1. NANOYOUTeachersTrainingKitinNanotechnologiesChapter4InformationandCommunicationTechnologies(ICT)MODULE1ApplicationsofNanotechnologiesWrittenbyLuisaFilipponiandDuncanSutherlandInterdisciplinaryNanoscienceCentreAarhusUniversity,DenmarkJanuary2010CreativeCommonsAttributionShareAlike3.0unlessindicatedintextorfigurecaptions.

2. NANOYOUTeachersTrainingKitModule2Chapter4ContentsIntegratedcircuits...........................................................................................................................5MoreMoore........................................................................................................................................................... 7MorethanMoore...................................................................................................................................................... 8BeyondCMOS............................................................................................................................................................ 9 Newdatastorageandprocessingnanotechnologies............................................................................................ 9Datastorage.................................................................................................................................11Theconceptofanuniversalmemory....................................................................................................................... 21Nanotechnologydevelopmentsindatastorage...................................................................................................... 21 MRAM.................................................................................................................................................................. 31 NRAMTM............................................................................................................................................................... 4 1 Phasechangememory ........................................................................................................................................ 4. 1Photonics.......................................................................................................................................15Photoniccrystals...................................................................................................................................................... 51 Applicationincommunication............................................................................................................................. 6 1 Propertiesofphotoniccrystals............................................................................................................................ 6 1 Fabricationofphotoniccrystals........................................................................................................................... 7 1Displays.........................................................................................................................................19OLEDs....................................................................................................................................................................... 9 1 ApplicationofOLEDs ........................................................................................................................................... 2 .2Page2of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 3. NANOYOUTeachersTrainingKitModule2Chapter4QuantumDotLightEmissionDiodes(QD/LED)....................................................................................................... 22Electronicpaper(epaper)....................................................................................................................................... 32 Nanotechnologiesforepaper............................................................................................................................. 4 2Informationstoragedevices.........................................................................................................25Nanotechnologiesintags........................................................................................................................................ 5 2Wirelesssensingandcommunication...........................................................................................27Wearablesensingtextiles........................................................................................................................................ 92This document has been created in the context of the NANOYOU project (WP 4 Task 4.1). All information isprovidedasisandnoguaranteeorwarrantyisgiventhattheinformationisfitforanyparticularpurpose.Theuser thereof uses the information at its sole risk and liability. The document reflects solely the views of itsauthors. The European Commission is not liable for any use that may be made of the information contained Page3of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 4. NANOYOUTeachersTrainingKitModule2Chapter4Chapter4: ApplicationsofNanotechnologiesInformationandCommunicationTechnologies(ICT)Nanotechnology in many respects is already a key player in ICT research and development, both inacademiaandindustry.Computermicroprocessorsandmemorystoragedeviceshavefollowedapathofminiaturization in the last 20 years that has naturally brought transistors to have dimensions lowerthan100nm.Therearenowchallengestocontinuethisminiaturizationpathbecauseasthematerialsofsemiconductors,metalsandinsulatorsarereducednanosize,quantumeffectsstarttopredominateanddetermine their properties. This is resulting in a number of issues. Nanotechnology offers theopportunitytoexploit,ratherthanavoid,quantumeffectsforthedevelopmentofthenextgenerationofintegratedcircuits.Asminiaturizationcannotproceedforeverwiththemethodsandtoolsthathavebeen used so far, new approaches will be needed. Nanomaterials, precisely for their quantumproperties,andnanotechnologytoolsallowthecreatingofnewdatastorageandprocessingmethods.ThesedevelopmentsarediscussedinthesectionIntegratedcircuitsandDatastorage.ThesessionPhotonics looks into details in this emerging technology for optocommunication. Another essentialcontributionofnanotechnologyisinthefieldofdisplays,whicharebecomingthinner,lighterandlessenergyconsuming.ThecontributionofnanotechnologyinthisareaiscoveredinthesessionDisplays.ButtheevolutionoftheICTsectorwillmostlikelygobeyondwhatweconsidertodayaselectronics(i.e., devices that perform a task for us). There are visions of having electronics embedded in ourclothing, in the environment around us in what is conceived as a network of devices that createambient intelligence. Although still more a vision than reality, there is intense research on therealizationofthetoolsrequiredtorealizeambientintelligence.ThischapterlooksatthesevariousapplicationsareasintheICTsectorandconsiderswhattheimpactofnanotechnologiescanbeineach. Page4of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 5. NANOYOUTeachersTrainingKitModule2Chapter4IntegratedcircuitsInthelate1960sGordonMoore,cofounderofIntel,madeamemorableobservationthatbecamelaterknownasMooresLaw.Heobservedthatthenumberoftransistorsonachiproughlydoubledeveryeighteenmonths.Originallythiswasonlyanobservationbutwaslateradoptedasanindustrygoal.Asamatteroffacttheprogressionintransistordensityonachipinthelast40yearshasfollowedMooreslaw(Figure1).Inordertokeepupwiththislaw,transistorshavebecomesmallerandsmaller.Thefirsttransistorwasabout1cmhighandmadeoftwogoldwiresseparatedby0.02inchesonagermaniumcrystal.ThelatesttransistorsfromIntel(PenrynandNehalem)have45nmfeaturessizesandinaquadcoreconfigurationhaveover731million transistors! These numbers give an idea of the enormousminiaturizationeffortsthathasbeenachievedbythesemiconductorindustry. Scalingdownoftransistorshasbeenthedrivingforceforanumber ofreasons.Transistorsarethebasicbuildingblocksoftheelements in an integrated circuit (microprocessor, mass memory, logic gatesFigure 1. Curve shows the increase etc).Integratedcircuitsarethecoreoftheinformationandmemoryin number of transistors on storage device that are an essential part of all electronics we use:computer chip, which follows fromcomputers,torefrigerators,tocars,mobilephones,etc.AstheMoores prediction of doubling sizeofthetransistorisreduced,itsdensityonachipincrease,whichevery 18 months. (Image credit: increasesthespeed,theamountofmemorystoredperareaandthehttp://commons.wikimedia.org/wiki/User:Wgsimon, Creative Commons numberoffunctionsthatcanbeintegratedonasingledevice.AttributionShareAlike3.0) TIP FOR TEACHER: To illustrate this ask students to describe the size and function of the first mobilephone they can remember. In the early 1990s it was just a phone, quite bulky and heavy. Later itbecamesmaller,lighter,andwithmorefunctionsthanjustbeingaphone.Nowadayswehaveallinonedevicesthatarephones,musicdigitalplayers,radios,photocameras,internetplatforms,andmore!The enormous advancements in computing that has characterized the last fifteen years (including theadvent of internet and the so called Information Area) has been enabled by the miniaturization of allelementsincomputerchips.Inthefuturehighperformancecomputingisexpectedtodeliverthetoolsthatwedonthaveyet,likearealtimelanguagetranslatororubiquitoussensing. Page5of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 6. NANOYOUTeachersTrainingKitModule2Chapter4Scalingdowntransistorscannotgoindefinitelywiththetoolsandmaterialswehavenow.Expertssaythat the Moores law will last until year 2015, perhaps few years beyond. Eventually, we will reach apointwherethetransistorissosmallthatquantumeffectsstarttopredominate.Inatransistortheonandoffstatearedeterminedbytheflow(ornot)ofelectronsthroughthenpjunction(gate).Atverylow dimensions (e.g., 1 nm) electrons will be able to pass through the gate via tunnelling, which is afundamentalquantumeffect(fordetailsseeChapter4inModule1Fundamentalnanoeffects).Another issue is power consumption and heat generation. This is an issue that all people using amodern cell phone experience daily. As the amount of functions integrated on a mobile phone havebeen increased, so it has the amount of power consumed (the type and battery lifetime has becomedeterminant on quality and performance of the device, and cost). This leads also to heat generation,whichatsmallerscalesbecomesevenmoreimportantandisconsideredaresearchpriority.Reducingofpowerconsumptionisalsocritical,notjustfortheperformanceofthedevicebutalsoforenvironmentalconsiderations(energysaving).In simple words, by continuing using the current technology, we will reach a stage of developmentwherefurtherscalingwillcreateoppositeeffectssuchasgrowingenergyconsumptioninstandbymode,andperformancerestrictionsinactivemode.NewtechnologieswillbeneededtoallowminiaturizationofelectronicsdevicesalongMoorescurve.WHATCANNANOTECHNOLOGIESDO?Currenttransistorsarealreadybelow100nm,sotechnicallythesemiconductorindustryalreadymakesuseofnanotechnologies.Continueminiaturizationoftransistorsusing the CMOS platform (denominated More Moore technology) has already produced transistorssmaller than 100nm. The line mark was passed around year 2000, and today transistors are 45 nm.AlthoughtheMoreMooreapproachdoesinvolveworkingwithmaterialswithnanoscalesizes(andrelatedfabricationmethods),ithasthetaskofscalingexistingCMOSprocessesandreachingtheCMOSlimit (meaning the size limit obtainable with this technology). Some consider this not to be truenanotechnology, since it does not make explicit use of the unique properties of nanomaterials(quantumeffectsetc.).Thisdevelopmentline,meaningdevelopingfundamentallynewapproachestoinformation processing and data storage, beyond what we use today such as selfassembly, or totallynewmaterials(suchasmolecularelectronics)belongstothedomaincalledBeyondCMOS.Inadditionto those two domains is the More than Moore domain, meaning technologies that providefunctionalitybeyondtraditionalcomputing(suchasintelligentsystemsthatcaninterfacewiththeuser Page6of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 7. NANOYOUTeachersTrainingKitModule2Chapter4andambient).Withoutgoingtoomuchintothetechnicaldetailswewilloutlineinthenextsessionstheimpactofnanotechnologiesinthesedomainsoftechnologyinnovation.MoreMooreSemiconductor components (microprocessors, mass memories, logic gates) will need to follow theminiaturization trend described by the Moore law to keep up with the industry demand (MoreMoore).Thismeansintroducingnewmaterialsandnewdevicearchitectures.Oneofthemostcriticalelementsincurrenttransistorsistheinsulatinglayerbetweenthetwogateelectrodes.Thislayerisnowmadeofsiliconoxide;asthetransistorismadesmaller,thethicknessofthislayerisreducedtoapointthatleakage(passageofelectronsbetweenthetwoelectrodeswhenvoltageisoff,i.e.,tunnelleakagecurrent)becomesaproblem.Inthelatestprocessorssilicondioxideisreplacedwithahighpermittivitymaterial (highk) for low power consumption. Hafnium compounds are the most promising highkmaterialsandarecurrentlyusedinIntel45nmtechnologygeneration(node).As the materials used in transistor change and smaller features are needed, the fabrication methodsusedinCMOSalsoneedtoevolve.Ingeneral,thelimitofthesmallestsizethatcanbecreateddependsonthetoolused.Featuresabout500nminsizecouldbefabricatedthroughopticallithography,butinorder to create smaller features extremeUV lithography was needed. Advancements in CMOStechnology have always implicated enormous investments for the development of fabricationtechniques able to deliver the required transistor size. As new materials are introduced in CMOStechnology, also new fabrication technologies need to be integrated. For instance the 45nm node iscreated using a fabrication process which is different from the conventional topdown lithographyapproach.HafniummaterialsarenormallydepositedusingtheAtomicLayerDepositionmethod(ALD)whichisabottomupfabricationmethod(forareviewoffabricationmethodsusedinnanotechnologiessee Chapter 7 in Module 1 (Fabrication methods). The method is believed to be used in the lastgeneration of Intel processors. Another nanofabrication method that is being considered to continuethe Moores law of miniaturization is Nano Imprint Lithography. Although there are numerousfabricationtechniquesthatcanbeusedtomakenanoscalefeatures(ofwhichtheScanningTunnellingMicroscopeisthemostpowerfulintermsofcapabilities),inthecontextofthesemiconductorindustryonly few are feasible candidates. Any new fabrication technique (different from conventionallithography) must satisfy a number of stringent requirements: resolution, defect rate, throughput(meaning being able of producing many features quickly), and must be easily integrated in currentfabrication facilities (otherwise a massive investment of money would be needed). Among all, nano Page7of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 8. NANOYOUTeachersTrainingKitModule2Chapter4imprint lithography seems to be the technology that at the moment can satisfy those needs and willmostlikelybethetechnologyusedforthefuture32nmand22nmnodes.Anotherkeyelementinintegratedcircuitswhichisstartingtocreateproblemsisthecopperconnectorsbetween the transistors. The effective resistivity of copper increases at smaller dimensions and theintegrity of the signal as it travels along the connector is becoming a major issue. Nanotubes andnanowires are now being considered as alternatives to conventional copper. Carbon nanotubes areconsideredanideamaterialsincetheycanbeoutstandingconductors(withalmostnullresistanceandheatdissipation),theyareextremelystrongmechanicallyandinerttochemicals.Thecurrentproblemisitsfabrication(purecarbonnanotubesarehardtoproduce)andalignment.MorethanMooreThe More than Moore domain refers to the development of functional components beyond thetraditional computing ones (microprocessors and memory). The future electronics will integrate aninterface with the real word (so called ambient intelligence) and will need to integrate not just aprocessor and memory, but also sensors, actuators, RF interfaces etc. They will also need to satisfy anumberofrequirements,suchaslowpowerconsumption,flexibility,thermalmanagement,andlastbutnotleast,cost.Nanotechnologiesaregoingtohaveanessentialroleinallthosesystems.InthelastpartofthisChapterweprovidesomeideasofwhatambientintelligencemightdoforusandwhatitmightimplyintermsofsocialandethicalconsequences.Adetailedanalysisofthetechnicalelementsthatwillbeintegratedinthesesystemsisnotcoveredhereas it would be too advanced for a highschool level. We will only outline that new materials andfabrication methods will be needed in order to integrate these smart multifunctional systems andconnect them with the outside word. Different nanodevices based on different technologies andprocesses will need to coexist within the same package. This is conceptually very different from thecurrent concept of multifunctionality where different packages with specific functionalities areseparated and added together only the end of the manufacturing process. In the future there will besysteminpackagesolutionwherethedifferentfunctionalitiesareintegratedinone3Darchitectureasthe package is constructed (nanosensors, nanoactuators, processors etc). This requires theheterogeneous integration of electrical and a nonelectric component, which in turn requires newmaterials to be developed (like plastic electronics). In the short term nanotechnologies will probablycontribute in improving the properties of current materials, for instance with the addition ofnanoparticles to adjust parameters such as electrical resistance, thermal conductivity, coefficient of Page8of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 9. NANOYOUTeachersTrainingKitModule2Chapter4thermalexpansionetc.Inthelongtermnanotechnologiesareexpectedtobeusedtodevelopnanoscaleinterconnectorsandselfassemblytechnologiestogobeyondcurrentarchitectures.BeyondCMOSIt was mentioned before that miniaturization of microprocessors and memory cells cannot continueindefinitely,andMooreslawwillnecessarilycometoahalt,ifthesameCMOStechnologyisused.Onthe other hand, miniaturization and system integration will surely continue to be fundamental in ourcommunication society, even more than today. Ubiquitous sensing, ambient sensing, constantnetworkingandcommunicationinanalwaysconnectedstatuswillmostlikelybepartofourfuture.Forthistobepossible,newmaterialsandprocessingmethodswillberequiredoncethedimensionsoftransistors become so small that quantum effects start to predominate. Nanotechnologies allowexploitingtheseeffectsandrealizethefuturegenerationofelectronicstostoreandprocessinformationwherequantumeffectsandothernanoeffectsdeterminethepropertyandfunctionalityofthedevice.Without going into too much details, below we describe some fundamental developments thatresearchersareworkingontoensurethatminiaturizationcancontinuebeyondtheintrinsiclimitsoftheCMOStechnology.NewdatastorageandprocessingnanotechnologiesMicroprocessors work on processing information through passage of an electrical signal. In the futureinformation processing will be done using a state variable different from electric charge, such as spin(spintronics), molecular states (molecular electronics), photons (photonics), mechanical state,resistance, quantum state (including phase) and magnetic flux. These new state variables will requirenew materials to be used (e.g., relying on spin implies using magnetic materials rather than asemiconductor)andnewfunctionalorganizationofthedevice(architecture).Below is a list of some new concepts that are being developed for processing and data storage thatmakeuseofstatevariablesdifferentfromtheconventionalonesusedinCMOS(electriccharge).Spintronics:thisisanewtypeoftechnologythatmakesexploitsthespinoftheelectron(ratherthanonly its charge) to store and process information. It requires thin layers of magnetic materials. Thegiantmagnetoresistance effect (GMR) represents the first type of this new technology, and is used inthe new generation memory devices like the Magnetic Random Access Memory, or MRAM (used forinstance in the Apple iPod). The GMR and data magnetic storage devices based on this effect arediscussedinthenextsessionDataStorage. Page9of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 10. NANOYOUTeachersTrainingKitModule2Chapter4Photonics:Anotherpossibilityistheuseofphotons(ratherthanelectrons)inthevisibleorIRrangetotransmitandprocessdata(opticalcommunication).Inthiscasesemiconductors(likesilicon)nolongercan be used since they cannot emit and transport light efficiently. Other materials (photonic crystals)engineeredatthenanoscaleneedtobeused.PhotoniccrystalsandtheiruseinopticalcommunicationarediscussedinthededicatedsectionPhotonicsofthisChapter.Quantumelectronics:thistermmeanstheexplicituseofthetunnellingeffecttotransportelectronsfrom the source to the drain of the transistor. One such transistor exists and is called singleelectrontransistor(SET).Inthistypeoftransistor,betweenthesourceandthedrainisaquantumdot:electronsmusttunnelthroughthisdotinordertogetfromthesourcetothedrain.Basicallythisislikehavingtwoelectrodes(sourceanddrain)separatedbyathininsulatingbarrierwithathirdelectrode(thequantumdot,orquantumisland)inthemiddleofthisinsulatinggap.Thetransportofchargefromthesourcetothequantumislandandthenfromthequantumislandtothedrainoccursviathequantummechanicalprocessoftunnelling. Carbon nanotube transistors: In many ways carbon nanotubes are considered a dream materialwhen it comes to electronics: they can be conductive (or insulating) depending on their chirality (andwhen they are conductive, they are extremely good electronic conductors, with little resistance andconsequently little heat dissipation); they are strong (mechanically) and chemically inert, they areresistant to high temperatures, and they can be functionalized with specific molecules to act asanchoring point. Carbon nanotubes are about 12 nm in width, they are as narrow as the doublestrandedDNAmolecule(themoleculethatcarriesourgeneticinformation).Soarrangingnanotubesintoelectroniccircuitrycouldallowminiaturizationbyafactorofabout100overthecurrentlimit.Molecularelectronics:moleculesinnaturalsystems(plants,animals)arearrangedinmacromolecularsystems (nanostructures) that perform numerous tasks which involve the transmission of charges,photonsetc.Thesemacromolecularsystemshavedevelopedthoughmillionyearsofevolutionandareinfactanexampleofexcellencewhenitcomestoefficiencyofwork!Oneexampleistheelectricflowinnervous signalling, or the control of charges in the ionic pump, or the absorption of light andtransmission of photos and charge in plant chlorophyll. The examples are numerous. Molecularelectronicsisabranchofnanosciencethatwantstomakeexplicituseofmolecularassembliesforthetransmission and storage of data. The field includes molecular wires, molecular switchers, molecularsensors and other hardware components of electronics. The idea is to assemble molecules innanostructures that can perform a specific function (such as transport of charge) depending on its Page10of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 11. NANOYOUTeachersTrainingKitModule2Chapter4configuration.Anexamplecanbeatwoterminaltransistorhavingthreebenzeneringsthatactasthechargetransfersite.Thecentralbenzeneringisfunctionalizedwithtogroups(NH2andNO2)thatmaketheoverallmoleculeverysusceptibletoanelectronicfield.Theelectricfieldcaninducethedistortion(twisting)ofthemolecule.Basicallythisgivesrisetoanelectronicdevicewhereifavoltageisapplied,the molecule twists in a way that the current flow is stopped; when the voltage is turned off themolecule springs back to its native conformation and current flows again. This is just one of manymolecularelectronicdevicesunderresearch.InordertofabricateandtestsuchsmalldevicenanotoolsliketheSTMareneeded.Thesetypesofdevicesarestillinaveryearlystageofdevelopmentbecauseofthetimerequiredtofabricateandtestthem.Also,inordertomakeanyusefulmolecularcircuitavastnumberofdevicesneedtobeorderlyarrangedandsecurelyfixedtoasolidsupporttopreventthemfrom interacting randomly one with the other. In the future molecular wires (for instance made ofconductivepolymerssuchaspolypyrrole)orcarbonnanotubescouldbecomeintegratedinintegratedcircuits,whichwouldnotablyreducethesizeofcomputerchips(wiresusedtodayuseabout70%oftherealspaceonachip!).DatastorageDatastorageisakeycomponentofmanydevicesthatweuseeveryday:computers(thatcontainbothaharddriveandRAM),mobiledevices(inwhichthememorymedianormallyisamemorycard,thinkofyourdigitalcamera),andportablemediaplayers(likeiPods,mobilephonesetc.thatuseFlashmemory).Datastoragetechnologiesincludetwomaingroups,harddiskdrives(havingamechanicalcomponent)andsolidstatedatastoragedevices,whichcanbefurtherdividedinvolatileandnonvolatile.Volatilemeans that memory is lost once the power is turned off; nonvolatile means that memory is retainedwhenthepowerofthedeviceisswitchedoff. Volatile memory storage devices today include mainly Static Random Access Memory (SRAM) andDynamicRandomAccessMemory(DRAM). Nonvolatile memory storage devices, like Flash memory, are used in mobile devices and portablemediaplayers.Eachtypeofmemoryhasitsadvantagesanddisadvantages:DRAMhasasmallermemorycellsizethanSRAM,thereforecanstoremoredatabutrequirestoberefreshedperiodically,consumingpowerand Page11of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 12. NANOYOUTeachersTrainingKitModule2Chapter4loweringspeed;.SRAMcanstorelessdatabutisfaster;flashmemoryisnonvolatile,makingitidealfordeviceswherepowerisoftenturnedoff.Memory storage devices are described by their capacity (amount of data in MB), memory density (afunctionofthecapacityandthesizeofthememorycell),lifetime(howmanyread/writecyclesitcanlastbeforeitdegrades),read/writespeedandcost.TheconceptofanuniversalmemoryThe need for memory storage devices with an everincreasing density capacity has been the drivingforceforthisindustry.ThemotivationhasbeentheneedtokeeppacewithMooreslaw(andthereforereducingthesizeofthememorydevices),andtheincreaseinmobiledeviceswhichdemandlowpoweroperationandlowstandbybattery.Thesetwotrendshavecatalysedthesearchforauniversalmemory,meaning a memory storage device that addresses the major technical challenges of existing memorytechnology (DRAM, Flash memory etc.), while combining the value proposition of eachspeed, densityandnonvolatility.Althoughauniversalmemoryisstillaconcept,researchforitsrealizationisintenseand new technologies that have been developed try to go in this direction. Nanotechnology is anessentialpartofallofthese.NanotechnologydevelopmentsindatastorageInthelastfewdecadesthedimensionofmemorystoragecellshasbeendecreasing,followingMooreslaw.Thiscontinuingsizereductionthoughhasledtomemorycellswithextremelysmalltransistors.Atthe current 90nm process node, SRAM and DRAM are beginning to suffer from a number of scalingissues. As the semiconductor is reduced in size, quantum effects come into play, and electrons canjump from the source to the drain by tunnelling or just by thermal motion. Also, other elementsbecome critical, like charge leakage due to silicon substrate crystalline defects. In Flash memory aninsulating layer of silicon oxide wraps the gate architecture and serves as a barrier for storing thechange.Asthislayerbecomesthinner,thechargecanstarttoleakoutofthedevice.Theseareonlyfewoftheproblemsfacingtodaymemorystoragedevelopment.To deal with these challenges, new concepts have been recently introduced, that make use offundamentalnanoconceptsandnanotechnologytools: Magnetoresistive Random Access Memory (MRAM), where each memory cell is made of twoferromagneticthinlayersseparatedbyaninsulatinglayer. Page12of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 13. NANOYOUTeachersTrainingKitModule2Chapter4 Ferroelectric RAM (FeRAM), similar in architecture to MRAM, but where a ferroelectric layersubstitutesthedielectriclayerResistiveRAM(RRAM),inwhichaconductionpathiscreatedthroughadielectricmaterial Phase transition memory, also known as phase change memory (PCM), which uses the phasetransitionfromcrystallinetoamorphousofamaterial. Nanotube RAM, a trademark on the company Nantero (NRAMTM), which uses carbon nanotubes todeterminememorystates.Each of these technologies has a different level of maturity and time will be needed before they cancompetewithFlashmemory.Howeveradevelopmentinthissectorisveryrapidandisprojectedthatby2012nanotechnologyenabledstoragedeviceswillaccountfor40%ofthetotalmemorymarket.MRAMMagnetic materials are used in Magnetoresistive Random Access Memory (MRAM), in which eachmemorycellconsistsintwomagneticthinfilmmaterialsseparatedbyanisolatinglayer.Magnetic multilayer nanocomposites (meaning very thin film made ofmagnetic materials)displaymagnetoresistanceproperties.Magnetoresistance is a phenomenon where the application of a DCmagnetic field changes the resistance of a material. In metals this effectoccursonlyatveryhighmagneticfieldsandlowtemperatures.In1988it Figure 2. Arrangement forwas discovered that a very pronounced effect, now known as the giant producing giantmagnetoresistanceeffect(GMR),couldbeobtainedinmaterialsmadeof Magnetoresistance:layersofnonmagnetic (butalternating layers of nanometre thickness of ferromagnetic material andconductive)materialnonmagnetic, yet conducting material (Figure 2). The magnetic layers alternating with oppositelyforming the multilayer can have their magnetization vector aligned magnetized (arrows)(parallel) or not (antiparallel), as in Figure 2. Polarity is persistent, ferromagneticlayers.therefore the device is nonvolatile. If current flows through the deviceandthelayershaveaparallelconfiguration,theresistanceislowerthaniftheyweretobeantiparallel.IntheMRAMmemorycell,thetwothinlayersofmetalsareseparatedbyathininsulatingmaterial.Thisgivesrisetoanotheraffectcalledtunnellingmagnetoresistance(TMR)effect.IncontrasttoGMR,TMRuses ultrathin nonconducting spacer layers, which renders the ferromagnetic layers electrically Page13of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 14. NANOYOUTeachersTrainingKitModule2Chapter4isolated.Electronscanthustunnelthroughthisbarrier1.AsintheGMReffect,thepassageofacurrentchanges the polarity of the magnetic material causing either a high or a low resistance across theinsulating barrier, which can be read as a 1 or a 0. To write data in such memory cells, a current ispassedthroughthecellwhichaltersthepolarityofthemagneticlayers.Some materials have been discovered having even larger magnetoresistive effects than layeredmaterialsandthisphenomenoniscalledcolossalmagnetoresistance(CMR).Thesematerials(e.g.,LaSrandLaCamanganites)haveapeculiarcrystalstructurethatisresponsiblefortheCMReffectandcouldhaveanumberofapplicationsinmemorystoragedevices.NRAMTMThe company Nantero, Inc. has introduced a new type of nonvolatile random access memory calledNRAMTM where the N states for nanotube since it uses carbon nanotubes. The nanotubes areassembledasfibresandaresuspendedperpendicularlyacrosstrenchesofetchedsiliconwafers.Attheendofthesilicontrenchisplacedacontactelectrode.Whenapotentialisappliedbetweenthefabricand the electrode, the fabric bends and touches the electrodes. The interaction is based on Van derWaals forces and remains also after the power is turned off. When the fibre is far away from theelectrode,thejunctionhasahighresistanceandthisisreadasa0state.Ascurrentispassed,andthefibretouchestheelectrode,thejunctionresistanceislowered,andthisisreadasa1state.Carbonnanotubes are produced used a method alternative to the conventional one (chemical vapourdeposition (CVD)) and which does not require high temperatures. The process developed by Nantero,Inc.allowsproductionofpurecarbonnanotubesatroomtemperature.ThisisanaddedadvantagetothetechnologyasCVDrequiredtemperaturessohightodamagetheotherconstituentsofthememorydevice. The NRAM is considered a very important development towards the concept of universalmemory, and it has the advantage that it is fabricated using current CMOS technology platforms: thisensuresimmediatemanufacturability.PhasechangememoryPhase change memory (PCM) (also named phase random access memory, PRAM) is another newconceptinnonvolatilememorystoragethatispromising.Itusesamaterial(chalcogenideglass)which1Thetunnellingeffectisaquantummechanicaleffectwhichoccurswhenasmallparticlepenetratesabarrierbyusingaclassicallyforbiddenenergystate.Thiseffectisbasedonthefactthatparticles,e.g.,electrons,shouldbetreatedmoreasawavethenahardsphere.Thankstothetunnellingeffect,anelectriccurrentwillflowthroughathinisolatingbarrierwhenavoltageisapplied.Page14of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 15. NANOYOUTeachersTrainingKitModule2Chapter4can be "switched" between two states, crystalline and amorphous, with the application of heat. Theamorphous state has high resistance and is used to represent 0, whilst the crystalline state has lowerresistanceandisassociatedwiththestate1.Among all, PRAM (or PCB) is considered the most promising advancement in nonvolatile memorysolutions.InFebruary2008NymonyxstartedshippingthefirstPCMprototypesforcustomerevaluation.TheproductisnamedAlverstone;itisa128MBPRAM,producedona90nmCMOSfabric.NymonyxisthenewSTMicroelectronicsandIntelnonvolatilememorycompany.Advancementinthistechnologyisproceedingfast,andonDecember2009NymonyxannouncedapapershowingthescalingofPCMtothe45nm lithography node for the first time on a 1 GB product with an effective cell size of 0.015m2.Nymonyxresearchersreportgoodelectricalpropertiesandreliabilityresults,confirmingthatPCMhasreached the maturity to become a mainstream technology for high density nonvolatile memoryapplications.PhotonicsPhotonics is the study of interaction of light with matter. The field first begun in the 1960 with theinvention of the laser. Ten years after, the invention of the optical fibre as a means of transmittinginformationvialightformedthebasisforopticalcommunication.Thefieldisnowenormousandconsistofmanysubdisciplinesandapplications,likelasertechnology,biologicalandchemicalsensing,displaytechnology,opticalcomputing,fibreoptics,photoniccrystalsandmore.In1987EliYablonovitchatBellCommunicationsResearchCentrecreatedanarrayof1mmholesinamaterialwitharefractiveindexof3.6.Itwasfoundthatthearraypreventedmicrowaveradiationfrompropagatinginanydirection.Thisdiscoverystartedtheresearchonphotoniccrystals,butittookmorethanadecadetofabricatephotoniccrystalsthatdothesameinthenearIRandvisiblerange.Nowadaysphotonics crystals are an important nanomaterial investigated with numerous applications and inparticularforopticalcommunication.PhotoniccrystalsA photonic crystal consists of a periodic structure made of dielectric materials that affects thepropagationoflight.Essentially,photoniccrystalscontainregularlyrepeatinginternalregionsof highand low dielectric constant. Photons (behaving as waves) propagate through this structure or not dependingontheirwavelength.Theperiodicityofthephotoniccrystalstructurehastobeofthesame Page15of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 16. NANOYOUTeachersTrainingKitModule2Chapter4lengthscaleashalfthewavelengthoftheelectromagneticwaves,i.e.~200nm(blue)to350nm(red)for photonic crystals operating in the visible part of the spectrum. Such crystals have to be artificiallyfabricatedbymethodssuchaselectronbeamlithographyandXraylithography.PhotoniccrystalsexistinNature.ForinstanceinChapter2ofModule1(Naturalnanomaterials)itwas shown how the beautiful blue wings of some butterflies own their colour to their internalnanostructurewhichisinfactaphotoniccrystalstructure.Anotherexampleisopals.ApplicationincommunicationPhotonic crystals are now receiving much attention because of their potentials in particular in theopticalcommunicationindustry.Thecurrentexplosionininformationtechnologyhasbeenenabledbythesemiconductortechnologyandtheabilitythefabricatematerialswheretheflowofelectronscanbecontrolledinthemostintricateways.Photoniccrystalspromisetogiveussimilarcontroloverphotonswith even greater flexibility because scientists have far more control over the properties of photoniccrystals than they do over the electronic properties of semiconductors. The goal of putting moretransistors on a chip (to make smaller and faster integrated electronic circuits) requires furtherminiaturization. This unfortunately leads to higher resistance and more energy dissipation, putting alimitonMooreslaw(whichpredictsadoublingofnumberoftransistorsperintegratedcircuitevery2years). Researches are considering using light and photonic crystals (in alternative to electronstravellinginwires)forthenewgenerationintegratedcircuits.Lightcantravelmuchfasterinadielectricmediumthananelectroninawire,anditcancarryalargeramountofinformationpersecond.Giventhe impact that semiconductor materials have had on every sector of society, photonic crystals couldplayanevengreaterroleinthe21stcentury.PropertiesofphotoniccrystalsPhotoniccrystalsaredesignedtoconfine,manipulateandcontrolthepropagationofphotonsinthreedimensions. The properties of a photonic crystal are determined by the radius of the holes (or otherfeatures like dielectric rods) forming the array, the periodicity of the holes (or rods), the latticestructure,thethicknessofthematerial,andtherefractiveindex.The properties of photonic crystals can be understood by doing an analogy with semiconductors. Ingeneralinasemiconductorthevalenceorconductionelectronscanmoveinaperiodicpotentialarisingfrom the positively charged ion cores (the nucleus). The potential is characterised by two areas ofallowed energy, which are separated by a region of forbidden energy, called the energy gap, which Page16of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 17. NANOYOUTeachersTrainingKitModule2Chapter4meansthattherearecertainwavelengthsthatwillnotpropagateinthelattice(i.e.,noelectronswillbefoundinthebandgapregion).Thisistrueforaperfectsiliconcrystal.However,forrealmaterialsthesituationisdifferent:electronscanhaveenergywithinthebandgapiftheperiodicityofthelatticeisbroken.Thiscanbetheresultofamissingsiliconatom,orthepresenceofanimpurityatomoccupyingasilicon site, or if the material contains interstitial impurities (additional atoms located at nonlatticesites).Dopingofsemiconductorsisintentionallydoneinmicroelectronics.Nowconsiderphotonsmovingthroughablockoftransparentdielectricmaterialthatcontainsanumberoftinyairholesarrangedinalatticepattern.Thephotonswillpassthroughregionsofhighrefractiveindexthedielectricalternatedwithregionsoflowrefractiveindextheairholes.Thisisanaloguetotheperiodicpotentialthatanelectronexperienceswhentravellingthroughasiliconcrystal.Ifthereislargecontrastinrefractiveindexbetweenthetworegionsthenmostofthelightwillbeconfinedeitherwithin the dielectric material or the air holes. This confinement results in the formation of allowedenergyregionsseparatedbyaforbiddenregionthesocalledphotonicbandgap.Sincethewavelengthofthephotonsisinverselyproportionaltotheirenergy,thepatterneddielectricmaterialwillblocklightwithwavelengthsinthephotonicbandgap,whileallowingotherwavelengthstopassfreely.Inasemiconductoritispossibletobreaktheperfectperiodicityofasiliconcrystallatticebyintroducingdefects(doping),andhaveelectronsintheforbiddenenergygapregion.Similarly,itispossibletocreateenergy levels in the photonic band gap by changing the size holes (or rods) forming the photoniccrystals.Thisintroducesanallowedfrequency(whichmeansanallowedwavelength)inthephotonicbandgap,andthephotoniccrystalactslikeawaveguide.Thereforeinsimplewordssemiconductorsconsistofperiodicarraysontheatomicscalethatcontroltheflow of electrons; photonic crystals consist of periodic arrays on the scale of wavelength of dielectricmaterialthatcontrolthepropagationoflightwaves.Creatingperiodicstructuresoutofmaterialswithdifferent dielectric properties (high and low refractive index materials) serves as waveguides. Opticalpropertiescanbeabsolutelyundercontrolbycontrollingthestructureandmaterialcompositionofthephotoniccrystal.FabricationofphotoniccrystalsThere are different approaches to build a photonic crystal. The first ones to report this idea wereYablonivich and John in 1987, who fabricated a crystal for microwave wavelengths. The fabricationconsistedofcoveringablockofdielectricmaterialwithamaskconsistingofanorderedarrayofholes Page17of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 18. NANOYOUTeachersTrainingKitModule2Chapter4anddrillingthroughtheseholesintheblockonthreeperpendicularfacets.Thematerial,whichbecameknown as "Yablonovite", prevented microwaves from propagating in any direction in other words, itexhibited a 3D photonic band gap. Despite this early success, it has taken over a decade to fabricatephotonic crystals that work in the nearinfrared and visible regions of the spectrum. For instance, forvisiblelightalatticedimensionof500nmapprox.wouldberequired,whichmeansfabricatingamaterialwithholesseparatedby500nm.Thisisanextremelydifficulttaskwhichrequiressuitablematerialsandprocessingtechniques.Insteadofdrillingholesonasurface,anotherapproachtocreateaphotoniccrystalistobuildthelatticeoutofisolateddielectricmaterialsthatarenotincontact,asillustratedinFigure3.If an entire line defect is introduced in the lattice in Figure 3 by removing an entire row of rods, theregionswheretherodshavebeenremovedactlikeawaveguide,andanallowedenergyleveliscreatedinthephotongap.Awaveguideislikeapipethatconfineselectromagneticenergy,enablingittoflowinonlyonedirection.Oneinterestingcharacteristicofsuchawaveguideisthatlightpassingthoughitcanturnverysharpcorners,whichisnottrueinafibreoptic.Figure3.Thisisascanningelectronmicroscopeimageofaphotoniccrystal.Theperiodicarrangementoftheholesinthematerialcontrolsthemovementoflightwithinthecrystal.Eachholehasadiameterofabout200nm.(Imagecredit:A.Faraon,StanfordUniversity,NISENetwork,www.nisenet.org,licensedunderNISEnetworktermsandconditions).IfonlyonerodiseliminatedinthelatticeinFigure9(orifitsdiameterischanged),aresonantcavityisformed,whichalsoputsanenergylevelintothegap.Asmentionedbefore,thisenergygapdependsontheradiusoftherod,whichprovidesanopportunitytotunethefrequencyofthecavity.Thisabilitytotunethelightandconcentrateitinsmallspacesmakesphotoniccrystalsusefulforfiltersandcouplersinlasers.In theory photonic crystal applications reach across the entire electromagnetic spectrum, from UV toradio waves. In practice the challenge is the nanofabrication of these devices. Novel nanofabricationmethods, including selfassembly approaches, will play an essential role for the development of thisfield. Page18of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 19. NANOYOUTeachersTrainingKitModule2Chapter4DisplaysDisplay technology has progressed enormously in the last decade. Until few years ago, we had bulkytelevisionswithCathodeRayTube(CTR)technology,andmobilephoneswithblackandwhitedisplaysthatcouldshowonlytext.Nowadays,LCDtelevisionsarebecomingthenormandmobilephonesthatcan show photos and movies are the norm, many even with touchdisplays. This progress has beenenabled by an intense research in the field which is motivated by a billiondollar industry and by theconstantneedformorefunctionaldevices,thatcombineportability,imageandvideoquality,lowpowerconsumption,andlowcost.Thicknessandflexibilityarealsobecominganimportantrequirement.Herewereviewsomelatestadvancementindisplaytechnologyandtheimpactthatnanotechnologieshaveintheir development. We will describe in details Organic Light Emitting Diodes (OLEDs), Quantum DotLightEmittingDiodes(QD/LEDs)andelectronicpaper(epaper).AnotherareaofdevelopmentisFieldEmissionDisplays(FED)whichinasenseistheprogressionoftheoldCathodeRayTechnologytothenanoscale. FED uses an element, like carbon nanotubes, as an electron source, striking a colouredphosphor.Thistechnologyisnotcommercialyetanditsataprototypelevel.OLEDsCurrentdisplaysrelymainlyontwoapproaches:LiquidCrystalDisplay(LCD)andPlasmaDisplayPanel(PDP). Those two technologies have basically replaced the old cathode tube technology for displayswhichisnowbeingphasedout.PDPrequiresmuchmoreenergythatLCDtooperateandiscurrentlynotassuccessfulasLCD,especiallyinatimewhereenergyconsumptionisamajorconcern.LCDtechnologyon the other hand is becoming extremely common due to a considerable price drop in the last fewyears.LCDdisplaysoffersanumberofadvantagescomparedtotheoldcathodetubetechnology: first of all displays are much thinner and less bulky due to theirinherentstructureandassembly,andtheyprovideamuchbetterimagequality.However, LCDs have two main problems that are connected to their inherentcomposition: first, LCD displays can be difficult to see at oblique angles, aseasily seen on a laptop computer; second, they require backlight, whichconsumespower. Figure 4. OLED films about 200nm thick. (Image credit: R. Ovilla,University of Texas at Dallas, NISENetwork, www.nisenet.org, licensed underNISEnetworktermsandconditions). Page19of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 20. NANOYOUTeachersTrainingKitModule2Chapter4TheneedforbacklightexplainswhyinaLCDblacklooksmorelikedeepgraythantrueblack.OLEDhaveemergedasanewtechnologythatoffersanumberofadvantagescomparedtoLCD.Inthistechnology, the display is formed of an emissive and conductive layer sandwiched between an anodeandacathode.AvoltageisappliedacrosstheOLEDsothattheanodeispositivewithrespecttothecathode. This creates a flow of electrons from the anode to the cathode; therefore electrons areremoved from the conductive layer, and added to the emissive layer. The conductive layer becomespositivelychargedandtheemissivelayernegativelycharged.Thiscauseselectronholestoappearattheboundarybetweenthetwolayers:electrostaticforcesinduceelectronsandholestogetcloserandtheyrecombine,emittingenergyasaphoton.Emissionisinthevisibleregionandthisiswhatgeneratesthecoloursinthedisplay.MoleculesusedinOLEDsasthenamesuggestareorganicmoleculeslikeorganometallicchelatesandconjugateddendrimers(twotypesofmacromoleculesthatcanreachthenanoscale).Themoleculescanbedirectlyevaporatedorprintedonthepolymersubstrate,whichisanotableadvantage,andcanleadtoverycomplexmultilayerstructures.Themoleculesaredepositedinrowsandcolumnsontotheflatcarrier(simplybyprinting)andtheresultingmatrixofpixelscanemitdifferentcolours.ThereforethecolourgenerationinanOLEDisfundamentallydifferentthaninaLCDwhichispoweredby a fluorescent lamp (backlight) that is colourfiltered to produce red, green and blue pixels. Thus,when a LCD screen displays full white colour, twothirds of the light is absorbed by the filters. ThisexplainssomefundamentaladvantagesofOLEDsoverLCD: OLED pixels directly emit light, it does not require backlight, thus consume less power than LCDs.WhenintheOFFmodetheOLEDelementsproducenolightandconsumenopower.OLEDshaveamuchbetterpicturequalitybecausetheynaturallyachieveahighercontrastratio.ForaviewerthemostnoticeableeffectisthattheblackareasinanOLEDappeartrueback. OLEDs can be much thinner and lighter than LCD panels. In addition, OLED can be printed onto anysuitablesubstrateusinganinkjetprintersotheycantheoreticallybeincorporatedinflexiblesubstrateswhichopensupnumerousnewdisplaypossibilities(rollupdisplaysordisplaysincludedinfabrics).UnlikeLCDs,OLEDpanelscanbeseenwellundersunlightandatdifferentangles. Page20of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 21. NANOYOUTeachersTrainingKitModule2Chapter4OLEDtechnologyiscurrentlyusedinsmalldisplays(OLEDSareusedinnumerouscolourcellphones)butis not established as television panels due to some challenges that the OLED technology encounters.Manyofthesechallengescanbeaddressedwiththeuseofnanomaterialsandnanotechnologies.First,theorganicmoleculesusedintheOLEDhaveaninherenttendencytodegradeintime.Increasinglifetime of OLEDs is a research priority. This is particularly true for the blue colour (for instance thelifetime of a blue OLED is 14,000 hours whereas a typical LCD panel has a lifetime of 60,000 hours).Muchresearchisdedicatedinthesynthesisandtestingofneworganicmoleculesthatcanincreasethelifetime of OLEDs. The problem of OLERD lifetime is particularly important in those electronics thatrequire long lifetime (e.g., televisions). In devices that are used intermittently (mobile phones etc.)lifespanislessimportant.ThisexplainswhyOLEDtechnologyisalreadyfairlydiffusedinmobiledevices.AsecondproblemisinthenatureofthetopcathodelayeroftheOLED,whichneedstobeatransparentelectrode. Currently (Indium Tin Oxide) ITO is used since it offers a combination of conductivity andtransparency. The problem is in the availability of ITO, which is becoming less available, and in itsprocess conditions, which is done using chemical vapour deposition. This deposition method requiresveryhightemperatureswhichlimitthetypeofsubstratethatcabbeused.ITOisslightlyopaqueandthisaffectsimagequality.AveryactivefieldofresearchisthesearchofsuitablenanomaterialstoreplaceITOinOLEDcathodes. Onepossibilityiscarbonnanotubes.CurrentlytherearenumerousmethodstofabricateCNTs(alternativetoCVD)likespraycoatingandrolltorollprinting.AlsonumerouscompaniesareemergingthatproduceCNTsandthepriceisdropping.AnotherissueinOLEDsisthattheorganicmoleculescontainedwithinareverysensibletowaterandother substances. Therefore coating and packing of the OLED components is of fundamentalimportance. One of the problems is that current packaging materials are either too brittle (which is aproblem in flexible screens) or require too high temperature during their production process, whichwoulddestroythedevice.Currentlyalternatedlayersoforganicandinorganicmaterialsareused.Thisgives some level of flexibility and blocks the entrance (although not total) or foreign substances.Nanomaterials could help solve this challenge: for instance recently a method was developed wherenanoparticlesareusedtofilltheporesintheseorganicandinorganiclayerswhichimprovedremarkablythepackagingonthesedevices. Page21of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 22. NANOYOUTeachersTrainingKitModule2Chapter4ApplicationofOLEDsOLED technology can be used for two main applications: displays and light sources. The possibility ofusing OLEDs instead of tradition light bulbs is very attractive in terms of energy consumption(conventional incandescent light loose most of their energy as heat). OLED technology is thusconsidered in light and signs. The potential of OLED technology in the energy sector is discussed inChapter3ofthisModule2(Applicationofnanotechnologies:Energy).Thesecondmainstreamapplicationisinthedisplayindustry.Currentlytheyareusedassmallscreensformobilephone,portabledigitaudioplayers(MP3),carradios,digitalcamerasetc.OLEDtechnologyinTVisjustappearingonthemarket.ThefirstcommercialOLEDTVwastheSonyXEL1commercializedin2007(intheUSatacostofabout2,500US$).InOctober2008SamsungannouncedtheworldslargestOLEDTelevision(40inch)withaFullHDresolutionof1920x1080pixels.Thesamecompanyshowcasedthe thinnest OLED display, only 0.05 mm, meaning thinner than paper. This opens up numerousopportunities.Clearlyallmajordisplaycompaniesareinvestingalotinthisnewtechnology.ThefactthatOLEDcanbefabricatedonflexiblesubstratesopensthedoortoOLEDsintextiles,labelsandotherflexiblematerials.QuantumDotLightEmissionDiodes(QD/LED)Quantum dots (QD) are another class of nanomaterials that are under investigation for making moreefficient displays and light sources (QDLEDs). These are nanoscale semiconductor particlescharacterized by emitting a specific colour based on the size of the nanoparticle. A minute change inparticlesizeresultsinatotallydifferentcolourtheyemit;forinstancea6nmdiameterparticlewouldglow red, while another of the same material but only two nanometres wide would glow blue. LightemissionfromaQDismonochromatic,thereforeisverypure.Asaconsequence,theiruseindisplayswouldleadtoimageswithexceptionalimagequality.ThemostexcitingpropertyofQDLEDs,though,isthat they use much less power then currently employed LCDs where light is filtered by numerouspolarisers. Like OLEDS, QD LEDs emit light, rather then filtering it, so for this reason QDLEDs areexpectedtobemoreenergyefficient.InJune2006,QDVisionannouncedafirstproofofconceptofaquantumdotdisplay. Page22of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 23. NANOYOUTeachersTrainingKitModule2Chapter4Electronicpaper(epaper)Epaperisadisplaytechnologythataimsatmimickingtheappearanceofordinaryinkonpaper.Thereare various technologies to create an epaper, among which electrophoretic paper is the mostestablished. Unlike conventional flat panel displays, electrophoretic displays rely on reflected ambientlight, rather than emission of light from the display, and can retain text or images without constantrefreshing, thereby requiring much less power. This means also that they can be used under sunlightwithouttheimagefading.Epaperisalsoverylightandflexible.Epaper has numerous commercial applications, such as ebooks (meaning ereaders that can displaythe digital version of a book), epapers, electronic labels, general signage, timetables at bus stations,etc.The first electronic paper was invented in the 1970s by Nick Sheridon(Xeron) and was called Gyricon. The technology behind electrophoreticpaper is fundamentally different that the one behind other displays. Herethe information display is formed by the rearrangement of chargedpigment particles in an applied electric field. The particles are titaniumoxide(TiO2)about1micrometerindiameter,dispersedinoilwhereadarkcoloured dye has been added, together with surfactants and chargingagents.Themixtureisplacedbetweentwoparallelconductiveplatesandavoltageapplied.Thechargedparticlemoveelelctrophoreticallytowardstheplatewiththeiropposingcharge.Whentheparticlesareonthefrontsideofthedisplay,theparticlesscatterlightandappearwhite;iftheyareatthebacksideofthedisplay,itlooksblackbecausetheincidentlightisabsorbed Figure 5. Gyricon eby the dye. The back electrode is divided in a number of small picture paper rolled up. (Imageelements,thepixels,sotheimageisformedbydeliveringtheappropriatecredit: Eugeni Pulido,voltagetothepixel(resultinginawhiteorblackpixel).Thereforetheimage Wiki Commons, Creativeiscreatedbyarepeatedpatternofreflecting(white)andabsorbingregionsCommons Attribute(black). ShareAlike3.0) Page23of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 24. NANOYOUTeachersTrainingKitModule2Chapter4 Developersimaginethatepaperwillbeasupport(imaginearolltokeepin yourpocket thatopensuponcommand)wheretodownloadinformation (from an overhead satellite, a cell phone network, or an internal memory chip)andthenisusedasareadingsupport,whichdoesnotrequirepower andcanbeseenundersunlightetc.Oncereadingisdone,thedevicecanbe rolledupagain,placedinthepocketandreused.Figure6.Anexampleofanepaperdevice(ImageAtthemomentthetechnologyislimitedtoblackandwhitebutnumerouscredit:ManuelSchneider, companies are investing a lot to develop a coloured epaper solution.WikiCommons,CreativeAnother issue is its low refresh rate, making electrophoretic paperCommonsAttribute unsuitable for displaying animation or video. Some newspapers areShareAlike3.0) alreadyofferingtotheirsubscribersepaperversionsoftheirprints.NanotechnologiesforepaperSomenewmaterialsareemergingaselementsofepaper.InMay2008UnidymandSamsungproducedthe first active matrix epaper device incorporating carbon nanotube as the transparent electrodes.Otherapproachesusephotoniccrystals,liquidcrystalsandothernanomaterials.Another developmentuses aFigure 7. A thermochromicthermochromicdisplaywhichcanbeeasilydisplayunderdevelopmentfabricated using softlithography. Theat the Hong Kongthermochromicmaterial isa University of Science andmicroencapsulated powder mixed inside aTechnology. (Image credit:polymer (PDMS, the polymer used in softlithography). The reprinted with permissionthermochromic material is dark green at room temperature but turns from Liu et al., paperlikewhite when heated above 60 C. Once the two components have been thermochromic display,mixed, they form a polymer composite that can be spincoated over a Applied Physics Letters(2007),90, 213508.substrate and, once it is cured, it forms a thin polymeric sheet that hasCopyright2007the characteristic (inherent of PDMS) of being very flexible but alsoAmerican Institute ofresistant to stretching etc. The thermochromic display is basically made Physics.)of a single layer of thermochromic sheet in which a conductive wire,which is shaped in the logo desired, is embedded. When a voltage is applied, an electric current isgenerated in the wire, which creates a localized heat. Above 60 C, the colour of the thermochromiccomposite in the area corresponding to where the wire is becomes white, and the image of the logo Page24of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 25. NANOYOUTeachersTrainingKitModule2Chapter4appears. The main limitation of this technology is that the image is created through a wire, and notpixels.InformationstoragedevicesNumerous miniaturized devices exist now that can store and transmit data. Two examples are smartcardsandsmarttags.Thesedeviceshavebeencreatedtomeettheneedtocollectandtransmitdatausinglessspace(chips)andwirelessly.Theapplicationofthesedevicescoverspersonaldatacards(epatents,ehealthcards,creditcardsetc.),tagsforpackageprotectionandtrackingetc.Thetrendinthedevelopment of these devices has been the one allowed by miniaturization: integration of morefunctionsinasmallerspace.Inthefuturethistrendwillcontinueandnanotechnologywillbemostlikelytheenablertechnology.NanotechnologiesintagsProducts are most commonly identified and tracked using alabel,whichisalsoacode;theonestillusedcommonlyisthebarcode. In the last years we have seen the emergence ofanother labelling and tracking system called Radio FrequencyIdentification (RFID). An RFID is a small, wireless integratedcircuit (IC)chipwitharadiocircuitandanidentificationcode Figure 8. RFID chip on a stick with barembedded in it. The advantages of the RFID tag over other codeontheoppositesite(Imagecredit:scanable tags (like barcodes) are that the RFID tag is small WikiCommons,Publicimage).enough to be embedded in the product itself (not just on itspackage);itcanholdmuchmoreinformation;itcanbescannedatadistance(andthroughmaterials,such as boxes or other packaging); and many tags can be scanned at the same time. RFID tags arealreadybeingusedinmanyways,forinstanceforlivestocktracking(attachedtotheearorinjectedintothe animal) or in the latest epassports. They are used in libraries, schools, transport systems (tollroads),tickets(parkingtickets),sports(racetiming)etc.Developersofthetechnologyenvisionaworldwheretheycanidentifyanyobjectanywhereautomatically.ThecurrentsizeoftheRFIDchipisnowaboutthesizeofadustmite,thesmallerisabout50x50m.Therearealreadysomedevelopmentsthatmakeuseofnanotechnology,inparticularintagsthataredirectedtowardstheauthenticationandtrackingofvaluableproductssuchasdrugs.Thegoalistoavoid Page25of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 26. NANOYOUTeachersTrainingKitModule2Chapter4counterfeitingandmakesurethatthedrugisnotreleasedinthewrongmarket(e.g.,blackmarket).OneexampleisatechnologydevelopedbyNanoInk,whichisthecompanythatownsthepatentoftheDipPenNanolithography(DPN)2instrument,whichwasinventedbythecompanyowner.Thecompanyhaddeveloped a technique of encrypting pills using the DPN. Each pill can be encrypted with informationaboutplaceanddayofmanufacture,targetmarketandexpirydate.Tomakethisencryptingtechnologyfully working, the same encrypting should be placed on the package of the drugs. Another methoddeveloped at the National Physics laboratory in the UK makes use of electron beam lithography toencryptpills.Thiswaythepillcarriesinformationinaverysecureway:aspecialsreaderisneededforittobedecoded.Also,theinformationissotinythatitcannotbeseenwiththenakedeye,makingitidealforcovertlymarkingthings.Another strategy for authentication, developed in particular for packing, has been developed byNanoplexTechnologies(US)istheformofnanobarcodes.Thenanobarcodesaremadeofnanoparticlesofgold,silverandplatinum,whicharegrownintostrips.Eachstripehasadifferentmetalcombinationwhichleadstoadifferentreflectivityofthestripe.Aspecialmicroscopereaderisneededtodecodetheinformation. Nanoplex can create different codes by alternating the stripe order. Billions of differentcodescanbemade.Eachuniquecodecanbeassociatedwithaproductwhichallowsthecompanytotrackwheretheproductisorhasbeen.ELSATOPIC:DevelopersofRFIDtechnologyimaginethatonedaywecouldplaceanRFIDinvisibletagoneveryobject,tofollowitslocation,transport,butalsotoensure(inthecaseoffoodpackages)theproductintegrityetc.RFIDtechnologycouldbetheultimatesolutiontotheftandfraud.However,insomecasesRFIDchipshavebeenimplantedintohumans;forinstancein2004,theMexicanAttorneyGeneralsofficeimplanted18ofitsstaffmemberswithonesuchchip(calledVerichip)tocontrolaccesstoasecuredataroom.TheuseofRFIDimplantablechipsisstronglyopposedbyprivacyadvocatesandsomehumanrightmovementslikeFriendsoftheEarth,warningofpotentialabuse.Theyhavedenouncedthesedevicesasbeing"spychips"whichcouldbeusedbygovernmentsleadingtoanincreasedlossofcivilliberties.Ifprivateemployersweretousethistypeofchipsontheiremployeestheywouldhaveaccesstoanincredibleamountofprivateinformation.Inaddition,privacyadvocatessaythattheinformationcontainedinthischipcouldeasilybestolen,sothatstoringanythingprivatecouldleadtoidentitytheft.Intermsofsafety,theFoodandDrugAdministrationhaswarnedin2004that these chips pose potential medical problems. Electrical hazards, MRI incompatibility, adverse tissuereaction,andmigrationoftheimplantedtransponderarejustafewofthepotentialrisksFDAhasidentifiedwiththeVerichipIDimplantdevice.2FordetailsontheDPNanditsfunction,seeChapter7ofModule2Fabricationmethods.Page26of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 27. NANOYOUTeachersTrainingKitModule2Chapter4WirelesssensingandcommunicationAt the moment electronics for us means basically devices, pieces of equipment that can offer us aservice (computation, information, entertainment and communication). The development path as wehaveseenitinthelastyearshasbeenaddingperformanceandcomplexitytothedevices.Oneofthevisions in the ICT industry is the concept of ambient intelligence: computation and communicationalways available and ready to serve the user is an intelligent way, meaning satisfying certainrequirements.Thevisionisthatelectronicswillbeembeddedinournaturalsurroundings(cloths,books,doors etc.), present whenever we need it, enabled by simple and effortless actions, attuned by oursenses,adaptivetousersneedsandactions,andtotallyautonomous.Theconceptofambientintelligentispartlystillasciencefictionvision,andtechnologiesarenotdevelopedyetthatallowthisvisiontoberealized.However,thevisionofinterfacingactivelyhumanandelectronicsisnottotallyabstract:thinkforinstanceoftheWiisystem,whichallowsapersontocommand(andplay)withsoftwaresimplybymoving from a distance, or virtual reality games and communication tools. The vision of ambientintelligence though is even more ambitious. Scientific progress and industrial investment are likely tomakeambientintelligence(oratleastsomeofitsconcepts)arealityinthefuture.Electronicdevicesintheintelligentambientworldwillbecomeagatewaybetweentheuserandtheambient. A fundamental requirement is ubiquitous sensing and computing: devices must be highlyminiaturised,integratedintheambient,autonomous,robust,andrequirelowpowerconsumption.Theyshould be created easily and survive without particular management. All of these requirements arelikelytobemetwiththeuseofnanotechnologies;belowwelistsomekeyelements: Miniaturization and system integration: Numerous different functions (logic, memory, radiofrequency, sensors and software) will need to be integrated on a single component. This implies newand severe demands onto the microelectronic, optoelectronic and microsystem components that arethebuildingblocksoftheInformationSocietytechnologies.Itmeansdevelopingnewmanufacturingtechnologies and materials that can allow reaching this advanced system integration at feasible costs.Nanotechnologies allow using nanosized material (carbon nanotubes, molecular electronics etc.) andrealizenanosystemstransistorshundredoftimessmallerthenthecurrentones.Miniaturizationisthegateway to reach a number of key elements: mobility, low power consumption, more performance,smallsizesandlowweight,lowcost,highreliability,moreflexibilityandubiquity.Fromchipstoembeddedsoftelectronics.Electronicsnowareintheformofsolid,rigidwafersorchips.Torealizetheconceptofambientintelligenceakeyrequirementisembeddingelectronicsin Page27of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 28. NANOYOUTeachersTrainingKitModule2Chapter4many different types of materials, from plastic to textiles. Organic electronics (meaning naturallyconducting molecules, such as polypyrrole) will have an important role. At them moment, organicmaterials are used in OLEDs (see dedicated Session in this Chapter), organic solar cells (discussed inChapter3ofthisModule2ApplicationofNanotechnologies:Energy),andinorganictransistors(stillat a proofofconcept stage). Although all these systems are still in development, research is veryintense and it is likely that organic electronics will become a key component in our future electronicdevices. The reason is that organic electronics are produced depositing and pattering thin films oforganic conductors, semiconductors or insulators. Organic films can be deposited in vacuum, but alsoinexpensivelyfromsolutionorviahighresolutioninkjetprinting.Processingtemperatureisalwayslow(below 200 C) meaning that organic thin films can be integrated with soft materials like plastics,openingthedoorstoflexibleorganicelectronics. Embedded sensors. One of the key enablers of ambient intelligence is the presence of sensorsembedded in the user and in the ambient it needs to communicate with to gather information andcommunicatedatawirelessly.Nanotechnologiesmayrenderthispossiblebyincreasingthesensoryskillsofhumansbasedonwearableorembeddedsensors(forinstanceinclothing)andtheabilitytoprocessthis enormous amount of sensory data through powerful computers. In order to achieve a trueintegration between the sensor element and the physical object the device should adapt to theenvironment that surrounds it: basically those devices should become intelligent in the sense thatlearningshouldbeakeypropertyoftheirsystem,similarlytothewaysystemsgrowandadaptinthebiologicalworld.Ambientsensorsshouldalsoberobust,surviveinharshenvironmentsorinthecaseofwearableelectronicssurvivewashing,beinexpensiveandecologicallysustainable. Integrated power sources. Power supply is crucial for all embedded electronics, being this wearable(e.g., electronics in clothing, shoes etc.) or embedded in objects surrounding the user. For instance inthecaseofwearableelectronics,wherelowpowersarerequired,theelectricalpowercouldbeeitherthebodyheatorthebodymovement.Althoughthefieldisinitsinfancy,researchisveryintenseinthisfield and some systems have been demonstrated in laboratories in the form of miniaturisedthermogenerators or miniaturized energy scavenger systems (these are discussed in Chapter 3 ofModule2ApplicationofNanotechnologies:Energy). Page28of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433 29. NANOYOUTeachersTrainingKitModule2Chapter4ELSATOPIC:Clearlytherealizationofthevisionofambientintelligencerequiresmeetingnumerousscientificand technical challenges. The time frame from vision to reality could be decades. In addition, the conceptitself brings about a number of fundamental ethical and social questions: what does it mean to be human?Whatdoesitmeantosense?Isitethicaltoaugment(andinterferewith)thewayhumansinteractwiththeirsurroundingambient?Doeshumanprogressneedthistechnology?Questionsofpersonaldataprivacyalsoarise. The questions are numerous and intense discussion on these fundamental ethic questions is alreadytaking place. Nanotechnologies, being an enabler of the ambient intelligence vision, are necessarily part ofthesediscussions.WearablesensingtextilesSensors could be inserted inside our clothes to gather information about our location, and otherenvironmentconditionsaroundus,suchastemperature,pressureetc.Thiswouldfacilitateenormouslythetaskoflocatingmissingpeople.Forinstanceajacket(orotherwearabletextile)withanintegratedGPSsensorcouldbecomeastandardinchildrenclothingtoensuretheirsafety.Otherelectronicscouldbecomeintegratedaswell,suchasphones,musicdevicesetc.Withtheadvancementofnanoelectronicsthosetypeofclothingcouldbecomeareality.NANOYOUDILEMMA:TheexampleofthejacketwithanembeddedGPSrepresentsthebaseforoneoftheNANOYOUdilemmapartoftheNANOYOURolePlayCardGame(seewww.nanoyou.eu/en/decide).Imaginethisjacketusedforchildrenclothing:itwouldallowparentstoalwaysknowthelocationoftheirchildren.Iftheygetlost,theycouldbeimmediatelylocated.However,woulditmakethemfeelliketheyareunderconstantsurveillance?Isthisagainstthefundamentalhumanrightoffreedom?Intelligent sensors are already a reality in the form of wearable sensing textiles that can monitorfundamental physiological parameters like heart rate, temperature, breath rhythm etc., withapplications targeting sport monitoring and prevention of cardiovascular risk. For instance the ItaliancompanySmartexhasdevelopedaprototypethatmeasuresalloftheseparametersincludingposture.TheinformationregisteredbythesensingtextileissendtoacomputerviaBluetooth.Thecompanyisalso part of a new European project called Biotex which aims at creating wearable textiles with evenmore sophisticated sensing capabilities. The aim is to create biosensingclothes that provide remotemonitoring of diagnostics body builds to improve early illness detection. The approach aims atdeveloping sensing patches, adapted to different targeted body fluids and biological species to bemonitored,wherethetextileitselfisthesensor.Page29of29TheresearchleadingtotheseresultshasreceivedfundingfromtheEuropeanCommunitysSeventhFrameworkProgramme (FP7/20072013)undergrantagreementn233433