advanced quartz sensor technology for fm-afm€¦ · of scanner elongation z, acquired at room...
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Key Features
•SensitiveandFast•Reliable•Adjustment-Free•SimultaneousAFM&STM•NanoManipulation•AFMinLiquids•KelvinProbeMicroscopy
ADVANCEDQUARTZSENSORTECHNOLOGYFORFM-AFM
KolibriSensor
INNOVATIONINSURFACESPECTROSCOPYANDMICROSCOPYSYSTEMS
SPECS leads the way in state-of-the-art technology for electron spectroscopy and scanning probe microscopy.
SPECSSurfaceNanoAnalysisGmbH
SPECS headquarters with more than 150employeesislocatedinthecenterofGermany’scapital Berlin, with subsidiaries in Switzerland(SPECSZurichGmbH)andintheUSA(SPECSInc.).Furthermore, we have liaison offices in FranceandSpainandarerepresentedallovertheglobebyoursalespartners.
State-of-the-art scanning probe microscopy sytems
Weareateamofscientistsandengineerswhohavebeendedicating theirknowledgeandexperienceto the development, design, and productionof instruments for surface science, materialsresearch,andnanotechnologysince1983.
Ourkeytosuccesisknow-how,experience,closecontact to scientists from all over the world,customer orientation, reliable quality control,anddynamicresearchanddevelopment.
Schematic diagram of a mechanical oscillator as used as a force sensor in FM-AFM. The tip is part of the oscillating mass m.
m
k
tip
sample
ADVANCEDQUARTZSENSORTECHNOLOGYFORFM-AFM
Frequencymodulationatomicforcemicroscopy(FM-AFM)isapowerfulscanningprobetechniqueto image a large variety of surfaces on lengthscales ranging fromseveralmicrometers to theatomic scale using a tip as a probe. FM-AFMis based on the measurement of quantitiesrelated to tip-sample interaction forces.A mechanical oscillator - characterized by itsspringconstantk,eigenfrequencyf0,andqualityfactorQ-isusedasaforcesensor.Thetipispartoftheoscillatingmassm.
InFM-AFM,theforcesensorisdriventooscillatewithconstantamplitudeA;resonanceisimposedvia the phase relation between the excitationforce and the tip oscillation. The oscillationfrequency fof the forcesensordependson tip-sample forces. The basic measured quantity inFM-AFM is the frequency shift Δf of the forcesensor, defined as the difference between theoscillation frequency f with the tip subject tointeractionforcesandtheeigenfrequencyf0.
The mechanical tip oscillation is convertedto an electrical signal (deflection detection).The frequency shift is measured by frequencydemodulationwithaphase-lockedloop(PLL).
Frequency Modulation Atomic Force Microscopy
KolibriSensor
AdvancedQuartzSensorTechnologyforFM-AFMThe KolibriSensor combines great forcesensitivity with high acquisition speeds. It isself-actuating and self-sensing. It is compatiblewith powerful tip preparation techniques. Withits great simplicity andhigh reliability, it allowsthe researcher to focus on the experiment,not the force sensor. Fast. Symmetric. Lasting.AtrueKolibri.
The KolibriSensor is manufactured employing a sophisticated micro-fab-rication process. Individu-ally tested and specified, the KolibriSensor is a reliable plug-and-play SPM sensor with outstanding performance.
The KolibriSensor from SPECS is a quartz sensor for simultaneous FM-AFM and STM. It features excellent signal-to-noise ratio. It is simple to operate and reliable.
ADVANCEDQUARTZSENSORTECHNOLOGYFORFM-AFM
Spectral noise density of the force gradient ΔkTS in the free-oscillation regime measured at room temperature. A = 100 pm, Q = 27,000, k = 540 kN/m. The bandwidth of amplitude and phase loop was 50 Hz and 100 Hz, respectively.
0 200 400 600 800 10000.000
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∆kTS S
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oise
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sity
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/m)/
√Hz)
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pect
ral N
oise
Den
sity
(Hz/
√Hz)
ΔkTS = 4 * Δf * k/fres
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FM-AFM image of the Si(111) (7x7) surface acqui-red at room temperature with an Aarhus SPM. A = 200 pm, ∆f = -0.3 Hz, 5 nm x 5 nm, 256 x 256 Pixel
SmallerAmplitudes
Oscillationamplitudesmaybesetbelow20pm.The high spring constant of the KolibriSensorenables stable oscillation, the low-noisedeflectiondetectionagoodfrequencyshiftsignalevenat small amplitudes. Small amplitudesarefavorable forhigh-resolutionFM-AFMandareaprerequisiteforsimultaneousSTMandAFM.
HigherQFactor
The KolibriSensor is based on a symmetricallength extension resonator. The center ofmass remains at rest and reaction forces arecompensated inside the quartz with minimallosses. Very high Q factors, resulting in lowfrequency noise and high force sensitivity, areachievedindependentlyofthesensormount.
25s/frame
sensitive
TheKolibriSensoristhemostsensitivequartzbasedAFMsensor
HigherForceSensitivity
ThepiezoelectromechanicalcouplingconstantoftheKolibriSensorisabouttentimeshigherthanthat of typical quartz tuning forks, the 1 MHzresonance frequency of the KolibriSensor is onthe order of 30-50 times higher. This results ina remarkably low deflection noise floor of lessthan1fm/√HzwiththeexternalKolibriPreamp™.This key advantage of the KolibriSensor resultsin fasterdataacquisitionandhigher resolution.Evenwith itshighspringconstantof540kN/m,the KolibriSensor has a signal-to-noise ratio anorder of magnitude better than typical tuningfork setups whenmeasuring the force gradient(forthesameQfactorandoscillationamplitude).This surprising and experimentally verifiedresult is due to the KolibriSensor’s very strongdeflectionsignal.
KolibriSensor
Fast
FM-AFMimagingwasneverasfastaswiththeKolibriSensor
IncreasedScanningSpeed
The slow scanning speed achieved when usingtypical silicon cantilevers or tuning forks forUHV FM-AFM with acquisition times of severalminutesperframeisaseverelimitationinmanyapplications. The KolibriSensor with its highresonance frequency of 1 MHz and excellentsignal-to-noiseratioovercomesthislimitation.ItenablesfasterdataacquisitioninFM-AFMimagingand force spectroscopy. Atomic resolutionFM-AFM is now possible with unprecedentedacquisition times below one second per frame,evenoninsulatingsubstrates.TheKolibriSensorfacilitates rapid characterization of surfacetopography on large scales at astonishingscanningspeeds.
FM-AFM image of KBr(001) acquired at room temperature with an Aarhus SPM.Upper: 0.8 Sec./Frame, 1.5 nm x 1.5 nm , 64 x 64 Pixel, A = 100 pm, ∆f = +3.0 HzLower: 300 nm x 300 nm, 256 x 256 Pixel, A = 200 pm, ∆f = +0.6 Hz
50 seconds/frame100 seconds/frame
8 seconds/frame25 seconds/frame
0 seconds 4 seconds
Constant height images on Au(111) of the frequency shift Δf and the tunneling current It, acquired simul-taneously with a KolibriSensor and an Aarhus SPM at room temperature, A = 300 pm.
Constant current STM image of graphene on Ru(0001) acquired with a KolibriSensor with oscillating tip and an Aarhus SPM at room temperature. U = +0.7 V, Iset = 50 pA, A = 100 pm
Frequency shift, tunneling current and dissipation on Si(111) (7x7) acquired simultaneously as a function of bias at room temperature with an oscillation ampli-tude A = 300 pm.
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accurate
FM-AFMandSTM–Simultaneous,andEachatitsBestWith small oscillation amplitudes, theKolibriSensor enables simultaneous STM andFM-AFM.Foracquisitionofthetunnelingcurrent,the KolibriSensor’smetal tip is providedwith aseparate electrical contact, which guaranteesclean separation of STM and AFM signals. TheKolibriSensor is also excellent for conventionalSTMwithnon-oscillatingtip.
Topographic FM-AFM images acquired in the short-range attractive and repulsive regime at room temperature with an Aarhus SPM.
Δf = +2.2 Hz, A = 100 pm
Au(111) Si(111) (7x7) KBr(001)
Δf = +0.44 Hz, A = 200 pm
Δf = +0.22 Hz, A = 200 pm
Δf = -0.37 Hz, A = 400 pm
Δf = -0.16 Hz, A = 300 pm
Δf = -0.50 Hz, A = 300 pm
KolibriSensor
FM-AFMatSmallDistances
With its extraordinary force sensitivity, the KolibriSensor is excellentfor high-quality atomic-resolution FM-AFM imaging on various surfacesincluding insulators. The sensor’s stable oscillation at small amplitudesenables imaging in both the short-range attractive (negative Δf) andrepulsive(positiveΔf)tip-sampleinteractionregime.
Characteristics of the frequency shift Δf and the dissipation in the free-oscillation regime as a function of scanner elongation z, acquired at room tempera-ture with a KolibriSensor mounted to the scanner of an Aarhus SPM. No dependence of the frequency shift and the dissipation, hence the sensor’s Q factor, on the scanner elongation is observed. f = 999175 Hz, Q = 27500, A = 100 pm
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z Position Scan Piezo (nm)
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sipa
tion
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)
Δf (m
Hz)
-150 -100 -50 0 50 100 150105.8
105.9
105.9
106.0
106.0
106.1
106.1
A = 100 pm
Characteristics of the tunneling current and the frequency shift on Si(111) (7x7) as a function of tip-sample distance acquired at room temperature with a KolibriSensor. U = 0.8 V, A = 300 pm
Tunneling Current forwardTunneling Current backwardFrequency Shift forwardFrequency Shift backward
Distance z (nm)
Tunn
elin
g Cu
rren
t (nA
)
Frequency Shift (Hz)
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9Spectroscopy
With its well defined electrical characteristics,the KolibriSensor is the ideal sensor forquantitative spectroscopy studies. What ismore, with its ability to simultaneously acquireforce and tunneling data, it is the ideal sensorforquantitativestudiesofrelationshipsbetweendifferent tip-sample interaction mechanisms.For instance, it is possible to simultaneouslymeasure the frequency shift, the dissipation,the tunneling current, and the differentialtunnelingconductance.
WellDefinedOscillation
The design of the KolibriSensor ensures anoscillation of the tip perfectly aligned withits longitudinal axis. In particular, there is notiltedoscillationas is typical forcantileversandsome tuning fork implementations. The directpiezoelectric excitation avoids excitation oflateral modes. Due to the symmetric layout ofthe quartz resonator, mechanical interactionsbetween the sensor oscillation and the sensormount are minimized. High Q factors arereproduciblyachievedindependentofthesensormountandelongationofascanner.
DissipationMeasurements
WiththeKolibriSensor,quantitativedissipationmeasurementsareeasyandaccurate.NocalibrationisnecessarysincethedissipatedpowerisdirectlyrelatedtotheunitsofVoltandAmpere.Dissipationofforcesensoroscillationenergyarises,whenthetip-sampleinteractionforceasafunctionofdistanceexhibitshysteresis.Dissipationprovidesvaluableinformationinmanycontexts.
Force map F(x,z) acquired on insulating KBr(001) along the line indicated in the inset. The measurement was done at room temperature with a KolibriSensor-equipped Aarhus SPM. Thermal drift was compensa-ted using the Nanonis Atom-Tracking module. A = 400 pm, total acquisition time 32 s
z po
sitio
n (n
m)
x position (nm)
Bias spectroscopy atop graphene and Ru(0001) surface sites measured at room temperature with an Aarhus SPM.
Topography (z) and local contact potential difference (UCPD) measured simultaneously by FM-KPFM on graphene grown on Ru(0001). Data acquired at room temperature with an Aarhus SPM.
Δf = -0.42 Hz, A = 500 pm,fmod= 65 Hz, Umod = 0.4 V, 550 nm x 550 nm, 0.25 lines /s
KolibriSensor
KelvinProbeForceMicroscopy
The local contact potential difference (CPD)relates to many surface phenomena, includingcatalytic activity, reconstruction of surfaces,and local charge distribution. The metallic tipof theKolibriSensormakes itan idealprobeformeasuring the local CPD by bias spectroscopyand frequency modulation Kelvin probe forcemicroscopy(FM-KPFM).
Versatile
TheKolibriSensorexcelsinvariousapplicationsofSPM
ForceMapping
Ideal for rapid acquisition of force-distancecharacteristics, the KolibriSensor is an excellentchoice formeasuring 2-D and 3-D force volumedata.
Surface of cleaved muscovite imaged in 1 M KCl buffer solution by FM-AFM with a KolibriSensor. Data acquired with an Aarhus SPM modified for imaging in liquids. A = 300 pm, Δfset = +140 Hz
Frequency response of a KolibriSensor with the tip oscillating in air (black) and in water (red), measured with an Aarhus SPM modified for imaging in liquids.
FM-AFM image of Si(111) (7x7), acquired at low temperature. T = 2.4 K, A = 69 pm, Q = 80,000, ∆f = -1.3 Hz. Courtesy of Toshu An, group of Prof. Hasegawa, The University of Tokyo.
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SPMinLiquids
TheKolibriSensor isprotectedbyasophisticatedmetal casing. The tip protrudes to the outsidethroughaholewith adiameterof only 100µm.The tipcanbe immersed inwaterwithoutwaterenteringthecasing,thesensor’sQfactorremainslarge.Sincesolelythetipisoscillatingintheliquidwhilethesensor’scasingandbaseareatrest,nospuriouspeaksarepresent.ThehighQfactorandexcellent noise floor below 1 fm/√Hzmakes theKolibriSensor an excellent force sensor for SPMin liquids. The KolibriSensor enables highest-resolutionFM-AFMinliquidswithunprecedentedeaseofuse.
LowTemperatureOperation
The adjustment-free, completely electronicself-sensing deflection detection makes theKolibriSensor ideal for low temperatureapplications where there is limited space,adjustment of optics would be complicatedor where complete darkness is important.The typical power dissipation of an oscillatingKolibriSensorisontheorderofPicowattsonly.
UpgradeyourSTMtoFM-AFM
The KolibriSensor features entirely electricexcitationanddeflectiondetectionbasedonthepiezoelectric properties of quartz. No externalactuatorsare required forexcitation.Deflectiondetection is adjustment-free. An excellentsignal-to-noise ratio is achieved with theexternal KolibriPreamp. Therefore, retrofittingexisting (low temperature) STM systems with aKolibriSensor for combinedSTMandFM-AFM isquickandeasy.
Scanning electron micro-graph of the KolibriSensor tungsten tip protruding from the sensor’s metal casing.
reliable
KolibriSensoriscommerciallyavailablewithguaranteedperformance
GuaranteedPerformance
The KolibriSensor’s high quality standard isachieved by employing a sophisticated micro-fabrication process, developed in collaborationwiththeSwisswatchmakingindustry.Eachsensoris tested at the factory. Resonance frequencyandQ factor are documented and provided onaspecificationsheet.
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KolibriSensor
Scanning electron micro-graphs of the same tip, before and after sputtering with a parallel oriented Ar+ ion beam (acceleration voltage 3.8 kV).
FIM image of a polycrystal-line KolibriSensor tungsten tip, measured at a tip bias of U = 3 kV with the tip held at room temperature.
PowerfulTipPreparation
The sensor’s metal casing enables simpleand powerful in-situ tip preparation andsharpening by parallel ion beam sputtering,field ion microscopy (FIM), field emission andevaporation. Parallel ion beam sputtering isan extremely powerful preparation techniquefor tungsten tips. It results in sharp, clean andoxide-free tips favorable for highest-resolutionSTMandFM-AFMimaging.Alsoblunttipsortipscontaminated after prolonged imaging on bulkinsulators or molecular films can be restoredby sputtering. As its tip canbe sputteredmanytimes,aKolibriSensorhasaverylonglife.
MetallicTipandMetallicShielding
The KolibriSensor is completely enclosed ina sophisticated metal casing, only the sharpetched tungsten tip protrudes outside througha tiny hole. The rugged casing not onlysimplifies handling. It provides electromagneticshielding, it limits crosstalk, it enables scanningcapacitance microscopy and powerful tippreparationtechniques.
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Spectral deflection noise density measured with the FEMTO HCA-2M-1M-C (red), a current-to-voltage converter, and the SPECS KolibriPreamp (black). Both measurements were conducted under identical condi-tions at room temperature with a KolibriSensor oscilla-ting at an amplitude of A = 10 pm and an Aarhus SPM.
KolibriSensor
KolibriPreamp
sPeCs KolibriPreamp™
HighestPerformanceDeflectionDetectionWith the new KolibriPreamp, the oscillationof the KolibriSensor can be detected withunprecedented precision. The noise floor isbelow 1fm/√Hz, one order of magnitude lowerthanachievedwithtraditionalcurrent-to-voltageconverter setups and lower than achievedwith even the best interferometric detectionsystems. With the KolibriPreamp, users of the
KolibriSensorcanobtain lower frequencynoise,enabling faster scanning speeds and smalleroscillation amplitudes. The KolibriPreamp wasdeveloped by FEMTO® Messtechnik GmbH andtakes advantage of their excellent know-howand experience with preamplifiers. Excellentcharacteristics are achieved also with relativelylongwiringdistancesbetweentheKolibriSensorand theKolibriPreamp’s input. InUHV systems,the KolibriPreamp is operated outside thevacuum chamber. The KolibriPreamp combineslowest-noisedeflectiondetectionwith thegreateaseofuseandreliabilityofexternalelectronics.TheKolibriPreampseamlesslyintegrateswiththeNanonisOscillationController.
KolibriPreamp Specifications
Bandwidth(-3dB) 250Hzto15MHz
Gain 0.7V/nm,10V/pC
NoiseFloor <1.0fm/√Hz
Max.OscillationAmplitude 7nm
Output/InputImpedance 50Ω/1GΩ@DC
SupplyVoltage/Current* ±15V/±100mA
PowerSupplyConnector* LEMO1S,3PinFixedSocket
*TheSPECSKolibriPreampisfullysupportedbytheNanonisOscillationController.
2.76
Ø9Ou
ter c
leara
nce
Ø2.5Cable clearance
Ø6
Top-view
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Test stage with KolibriReceptor
KolibriReceptor
SPECS KolibriReceptor Specifications
Springs CuBe
Baseplate Al2O3
SpringContacts CuBeGoldplated
Weight 0.12g
Cables 3xcoppercoax,ø0.35mm,l=30cm
Kolibrisensor starter Kit
GettingStarted
SPECS provides a plug-and-play starter kitcomprising all components required to learnmoreaboutsensoroperationandhandling.
Thestarterkitcontains:
•ThreeKolibriSensors(native)•SPECSKolibriPreamp
•TeststagewithKolibriReceptor•SpecialtweezerstohandleKolibriSensors•Lownoisecablingfordirectconnectionof
theNanonisOscillationController
•Stand-aloneNanonisOscillationController
Kolibrireceptor™
PreciseKinematicMount
The KolibriReceptor is a precise kinematicmount with reliable electrical contacts for theKolibriSensor.ItisfullyUHV,lowtemperature,andhighmagneticfieldcompatible,andcanbedirectlyused as a building block in advanced scanningprobemicroscopedesigns.Thelightweightdesignallowsdirectmountingtoascanner.Thesnap-inmechanism allows inserting and removing thesensorwithawobblestickorevenwiththecoarsepositioningsystemoftheSPM.
Sensor weight: 0.4 gScrew socket material/height: Al2O3/0.635 mm
Ø123
2
1Top-view
Ø2.2Ø4.5
Ground contact (4)on backside
KolibriSensor
Bruker Adapter with KolibriReceptor fitting the Bruker MultiMode SPM head. Cable: 3x copper coax, ø 0.35mm
Kolibrisensors in Various Forms
KolibriSensorisavailableinvariousadaptationsfordifferentsystems
KolibriSensorBrukerAdapterKit
SPECSprovidesaplug-and-playkitcomprisingallcomponentsneededtostartimagingwithBrukerMultiMode®SPMs.
Thekitincludes:
•ThreeKolibriSensors(Native)•SPECSKolibriPreamp
•BrukerAdapterwithKolibriReceptor•SpecialtweezerstohandleKolibriSensors•Lownoisecablingfordirectconnectionofthe
NanonisOscillationController
ScrewmountKolibriSensor
The Screwmount option provides a convenientwayformountingandelectricallycontactingtheKolibriSensorbymeansofthreescrews(M1.6).
Sensor weight: 0.2 gClamp socket material: Stainless steelCable: 2x copper twisted pair
Sensor weight: 0.4 gHandle plate material/height: Al2O3/0.635 mm
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KolibriSensorforAarhusSPM
The KolibriSensor for the SPECS Aarhus SPMfeatures a socket for clamp insertion. Directcablingtothesensorisprovided.
KolibriSensorforTyto™SPM
The KolibriSensor for the SPECS Tyto SPM isdesignedformanipulationwithawobblestick.
Sensor weight: 0.11 gSubstrate material/height: Al2O3/0.4 mmCap material: TitaniumSensor without casing on request
KolibriSensor
SPECS KolibriSensor Specifications
ResonanceFrequency 1MHz
QFactor 10,000–100,000
TipMaterial/Weight Tungsten/1µg
SpringConstant 540kN/m
PiezoCoupling 65µC/m
NoiseFloor <1fm/√Hz
TypicalOscillationAmplitude 100pm
NativeKolibriSensor
sample
A
1: Uexc 2: Iosc
3: Itunnel
casing
oscillatingquartz rod
4
wire
metallic tip
1mm
PLL: Nanonis OC
Output: Excitation
Input: Oscillation
Tunneling Current
Any STM Preamp
SPECS KolibriPreampQuartz oscillator
Tip
19
Schematic Drawing
Equivalent Circuit
Recommended Instrumentation
NanonisOscillationControllerfortheFinestControloftheKolibriSensorThe Nanonis Oscillation Controller providesa convenient and proven way to drive theKolibriSensor. It affords both high-stabilityamplitude control and low-noise frequencydemodulationinasingledevicefullyintegratingwith the Nanonis SPM Control System.TheNanonisOscillationControllerfeaturesultra-low input noise, extreme frequency stabilityand highest frequency resolution essentialto take full advantage of the KolibriSensor.The control parameters for amplitude controlandfrequencydemodulationareuseraccessibleand can be auto-tuned using the uniqueperfectPLL™algorithm.
CompleteSPMSolutionsfromSPECS
For complete high-performance SPM solutionsincorporating KolibriSensor technology pleaserefer to our separate brochures on the provenAarhus SPM family offering extreme stability,speed, and highest productivity on a dailybasis inthetemperaturerangeof90Kto400K(1300 K optional), or the revolutionary SPECSultra-low temperature microscope JT-SPMwith lowest cryoliquid consumption foratomic manipulation and highest-resolutionspectroscopy at temperatures down to below1 K with 4He (below 500mKwith 3He optional)andoptionallyinmagneticfieldsupto3T.
sPeCsSurfaceNanoAnalysisGmbHVoltastrasse513355Berlin / Germanywww.specs.com