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BAYINDIR RESEARCH GROUP

JOURNAL CLUB

Nanotech 2011, Boston

PRESENTER(S): OSAMA TOBAIL

ARTICLES:

Carbon Nanotube Computer (Nature Sep. 2013)

Sub 10-nm Carbon Nanotube Transistor (ACS Nano Jan 2012)

http://bg.bilkent.edu.tr/jc/jc.html10/7/2013

BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr

TITLE

210/7/2013

The miniaturization of electronic devices has been the principal driving force behind the semiconductor industry,and has brought about major improvements in computational power and energy efficiency. Although advanceswith silicon-based electronics continue to be made, alternative technologies are being explored. Digital circuitsbased on transistors fabricated from carbon nanotubes (CNTs) have the potential to outperform silicon byimproving the energy–delay product, a metric of energy efficiency, by more than an order of magnitude. Hence,CNTs are an exciting complement to existing semiconductor technologies1, 2. Owing to substantial fundamentalimperfections inherent in CNTs, however, only very basic circuit blocks have been demonstrated. Here we showhow these imperfections can be overcome, and demonstrate the first computer built entirely using CNT-basedtransistors. The CNT computer runs an operating system that is capable of multitasking: as a demonstration, weperform counting and integer-sorting simultaneously. In addition, we implement 20 different instructions from thecommercial MIPS instruction set to demonstrate the generality of our CNT computer. This experimentaldemonstration is the most complex carbon-based electronic system yet realized. It is a considerable advancebecause CNTs are prominent among a variety of emerging technologies that are being considered for the nextgeneration of highly energy-efficient electronic systems3, 4.

http://www.nature.com/nature/journal/v501/n7468/full/nature12502.html#ref1





First computer made of carbon nanotubes is unveiled

310/7/2013

First computer made of carbon nanotubes is unveiledBy James Morgan Science reporter, BBC News, 25 September 2013

Cedric

Max Shulaker with Cedric, the first carbon computer: "There is no limit to the tasks it can perform".

Max


Cedric, Is it the start of Si age end?

410/7/2013

Cedric's vital statistics• 1 bit processor• Speed: 1 kHz• 178 transistors• 10-200 nanotubes per transistor• 2 billion carbon atoms• Turing* complete• Multitasking

How small is a carbon computer chip?• 100 microns - width of human hair • 10 microns - water droplet• 8 microns - transistors in Cedric• 625 nanometres (nm) - wavelength of red light• 20-450 nm - single viruses• 22 nm latest silicon chips• 9 nm - smallest carbon nanotube chip• 6 nm - cell membrane• 1 nm - single carbon nanotube

The transistors in Cedric are built with "imperfection-immune" designCedric can only count to 32, but in principle it could count to 32 billion

*After Alan Turing: general purpose computer is called Turing equivalent or Turing complete.

http://www.bbc.co.uk/news/technology-13283882


Background

510/7/2013

MIPS (Microprocessor without Interlocked Pipeline) Architecture, From Wikipedia

How Microprocessor execute programs?


TITLE

610/7/2013

The miniaturization of electronic devices has been the principal driving force behind the semiconductor industry,and has brought about major improvements in computational power and energy efficiency. Although advanceswith silicon-based electronics continue to be made, alternative technologies are being explored. Digital circuitsbased on transistors fabricated from carbon nanotubes (CNTs) have the potential to outperform silicon byimproving the energy–delay product, a metric of energy efficiency, by more than an order of magnitude. Hence,CNTs are an exciting complement to existing semiconductor technologies1, 2. Owing to substantial fundamentalimperfections inherent in CNTs, however, only very basic circuit blocks have been demonstrated. Here we showhow these imperfections can be overcome, and demonstrate the first computer built entirely using CNT-basedtransistors. The CNT computer runs an operating system that is capable of multitasking: as a demonstration, weperform counting and integer-sorting simultaneously. In addition, we implement 20 different instructions from thecommercial MIPS instruction set to demonstrate the generality of our CNT computer. This experimentaldemonstration is the most complex carbon-based electronic system yet realized. It is a considerable advancebecause CNTs are prominent among a variety of emerging technologies that are being considered for the nextgeneration of highly energy-efficient electronic systems3, 4.






SUBNEG and program implementation

710/7/2013

MM Shulaker et al. Nature 501, 526-530 (2013) doi:10.1038/nature12502

SUBNEG = Subtract and Branch If Negative

Example of non-pre-emptive multitasking


Schematic of CNT computer

810/7/2013


Timing diagram of the CNT computer:The lines show the waveforms corresponding to each signal; of particular note are the transitions of the lower five signals with respect to the clock signals.

Schematic of the entire CNT computer:composed of the four subunits: 1. instruction fetch, 2. data fetch, 3. arithmetic operation4. write-back.

All components apart from the memory are implemented entirely using CNFETs.

Logic gates and latches are built fromTransistors (CNFETs)


Characterization of CNFET subcomponents

910/7/2013


The CNFET computer is composed of 178 CNFETs, with each CNFET comprising ,10–200 CNTsAll p-type-transistors logic circuits


CNT computer results

1010/7/2013



Extended Data Figure 1: Fabrication flow for the CNT computer

1110/7/2013

I. prepare the final substrate for circuit fabrication

II. transfer the CNTs from the quartz wafer (where highly aligned CNTs are grown) to the final SiO2 substrate

III. continue final device fabrication on the final substrate


Extended Data Figure 2: Multibit arithmetic unit

1210/7/2013


Extended Data Figure 2: Multibit arithmetic unit

1310/7/2013


Extended Data Figure 3: Internal versus external connections of CNT computer

1410/7/2013

a, Schematic of the CNT computer, showing that all connections are fabricated on-chip and that only signals reading or writing to or from an external memory are connected off-chip. b, SEM of the CNT computer, showing which connections are made to and from the CNT computer from the probe pads. The SEM is colour-coded to match the coloured wires in a.


Extended Data Figure 4: PMOS-only logic schematics

1510/7/2013

a, Schematic of PMOS-only inverter. b, Schematic of PMOS-only NAND gate.

A B O/P0 0 10 1 11 0 11 1 0


VLSI-compatible Metallic CNT Removal (VMR)

1610/7/2013

N. Patil et.al. IEEE Transaction on Nanotechnology (2011)


Title

1710/7/2013


Motivation

1810/7/2013

Within the next decade, computing technology will require transistors with channel length below 10 nm

ROBERT F. SERVICE, 20 FEBRUARY 2009 VOL 323 SCIENCE

New material needed for sub 10nm devices


Single Wall Carbon Nanotubes provide a solution

1910/7/2013


Device Fabrication

2010/7/2013

Figure S1. (a) SEM image of aligned CNTs after transfer onto substrate with local bottom gates. CNTs are ~50 µm long, extending from one catalyst stripe (bright, vertical line) to another. (b) AFM image of nanotube used for diameter extraction. Average diameter was obtained from several AFM images. (c) SEM image of a set of devices on a single CNT showing how the staggered source/drain contacts enable a variety of channel lengths, including sub-10 nm. (d) Cross-sectional TEM image showing the sidewall structure of the contacts and a sub-10 nm channel.


Device characterization

2110/7/2013


Device characterization - evaluation

2210/7/2013


Device characterization - evaluation

2310/7/2013


What can we do?

2410/7/2013

Device modelling based on experimental results

Tube separation, alignment for better quality devices

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bayindir research group journal club · bayindir research group journal club nanotech 2011, boston...

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