Microsystems LaboratoryUC-Berkeley, ME Dept.

1Liwei Lin, University of California at Berkeley

Introduction to Nanotechnology and Nanoscience – Class#10

Liwei Lin

Professor, Dept. of Mechanical Engineering Co-Director, Berkeley Sensor and Actuator CenterThe University of California, Berkeley, CA94720

e-mail: lwlin@me.berkeley.eduhttp://www.me.berkeley.edu/~lwlin

Microsystems LaboratoryUC-Berkeley, ME Dept.

2Liwei Lin, University of California at Berkeley

Outline

CNT ApplicationsHW#4Paper 4CNT Supercapacitors

Microsystems LaboratoryUC-Berkeley, ME Dept.

3Liwei Lin, University of California at Berkeley

CNT Membrane

Microsystems LaboratoryUC-Berkeley, ME Dept.

Properties of CNT and Graphene

4Liwei Lin, University of California at Berkeley

Nature Nanotechnology 7,562–566 (2012)http://www.extremetech.com/wp-content/uploads/2013/02/elephant.jpg

Microsystems LaboratoryUC-Berkeley, ME Dept.

Electromigration is a problem for metal wires at small sizes• Covalent structure of CNT

prevents similar breakdown

Nanotubes For Wiring

Nanotube current densityis enormous

J ~ 105 A/cm2 J ~ 109 A/cm2

Contact resistance is necessarily large with this fabrication

Microsystems LaboratoryUC-Berkeley, ME Dept.

6

HW #4

Microsystems LaboratoryUC-Berkeley, ME Dept.

7Liwei Lin, University of California at Berkeley

HW #4

Microsystems LaboratoryUC-Berkeley, ME Dept.

Microsystems LaboratoryUC-Berkeley, ME Dept.

How CNT Field Emission Display works

9Liwei Lin, University of California at Berkeley

Diamond and Related Materials 10 2001 265-270

https://xja419.wordpress.com/2011/02/20/fed-field-emission-display/

Carbon Nanotubes — the Route Toward Applications

Renjie Tao

Carbon nanotubes—Structure

single-wall (SWCNT) multi-wall (MWCNT)

(n, m)

n = marmchair

n = 0

zigzagor m = 0 other

chiral

metal semiconductor

Thermo conductivity

Carbon nanotubes—Properties

3000 W/m*K (greater than that of natural diamond)

Superconductivitytransition temperatures: 5 K for 0.5-nm-diameter SWNTs

Stiffnesshigh Young’s modulus (0.64 TPa) and high tensile strength

modulus and strength are19 and 56 times that of steel wire

Single-wall

Carbon nanotubes—Synthesis and Processing1. carbon-arc discharge 2. laser ablation of carbon 3. chemical vapor deposition

SWNTs are presently produced only on a small scale and are extremely expensive ($750/g)All currently known synthesis methods for SWNTs result in major concentrations of impurities

Multi-wallCommercial access to MWNTs is less problematic

metallic, semiconducting, multi-wall

Important for electronic devices, displays, and nanoscale actuators

Patterning

Pattern catalyst first, nanotubes selectively growth afterwards

The Application of Carbon NanotubeMin Chen, Feb 24 2020

The Application of Carbon NanotubeIf the materials don’t have the real application for a long time, it will no longer be popular

Energy Storage

Hydrogen

Super Capacitors

Li‐ion Battery

Electrochemical DevicesThe advantages of carbon nanotube in making electrochemical devices

Accessible surface area of porous nanotube arrays

High electronic conductivity

Useful mechanical properties

Double layer charge injection 

Super Capacitors Electrochemical actuators

Lithium ion battery

Electrochemical DevicesSuper capacitors

Capacitance=

Concentric cylinders:

R1≈R2, R1/R2≈1ln(R1/R2) ~0, C ↑

Advantages:

Supercapacitors with carbon nanotubeelectrodes can be used for applications thatrequire much higher power capabilities thanbatteries and much higher storage capacitiesthan ordinary capacitors.

The capacitances (180 and 102 F/g forSWNT and MWNT electrodes, respectively)and power densities (20 kW/kg at energydensities of 7 W∙hour/kg for SWNT electrodes)

MnO2 ( 200‐600F/g ) NiO ( 400‐900F/g ) (recently)

Electrochemical DevicesElectromechanical Actuators

Nanotube electromechanical actuators function at a few volts, compared with the 100 V used for piezoelectric stacks and the 1000 V used for electrostrictive actuators.

Nanotube actuators have been operated at temperatures up to 350°C, and operation above 1000°C should be possible

The maximum observed isometric actuator stress of SWNT actuators is presently 26 MPa 

100 times that of the stress generation capability of natural muscle, and it approaches the stress generation capability of high modulus commercial ferroelectrics (40MPa)

Problem needs to solve: Creep

Electrochemical DevicesLithium‐ion Battery

Electrodes

high reversible component of storage capacity at high discharge rates

Maximum reported reversible capacity is 1000mA∙hour/g for SWNTs372mA∙hour/g for graphite and 708mA∙hour/g for ball‐milled graphite

Limitations:• The large irreversible component to capacity (coexisting with the large 

reversible storage capacity)• Absence of a voltage plateau during discharge• The large hysteresis in voltage between charge and discharge

Hydrogen StorageExperimental reports of high storage capacities are so controversial that it is impossible to assess the applications potential(2002)

Metal‐Organic Frameworks(MOFS)

Carbon Nanotube Composites (1st Commerical application)

Electronic conductivity: obviously improved by low loading level

Mechanical Properties: modulus and strength dramatically increased

Example: Vickers Hardness increased up to 3.5 times when loading 2% SWNT in Plastics

Field Emission Devices: Mechanism

• Electric field applied• Electrons emitted from nanotube• Field directs electrons to phosphor• Phosphor lights up from current• Enhanced with open SWNT or MWNT

Field Emission Devices: CNT vs Metal

• Discrete vs continuous energy states• Easier manufacturing

• Metals deteriorate easier, less vacuum required for CNT – 10^‐8 vs 10^‐10 torr• CNT can be screenprinted

• Stable emission• Long lifetime• Low threshold potential• Requires 4 mA/cm^2, vs 10 mA/cm^2 for metal

Field Emission Devices: Applications

• Flat panel displays• Lamps – good efficiency, long lifetime (8,000+ hours)• X‐ray – medical imaging – metal instead of anode, improved quality

• Microwave generation – very high current density required• Advantages over LCD: power consumption, brightness, viewing angle, response rate, operating temperature range

• FED still require advancements in: circuitry, low‐voltage phosphors, maintaining vacuum, spacers under high electric fields, elimination of faulty pixels

Nanotubesin Nanometer-Sized Electronic Devices

Instructor: Prof. Liwei LinPresenter: Kamyar Behrouzi

Course: ME218NSpring 2020

What Do We Need to Realize Nanoelectronics?

• Different Device Materials• Different Architectures• Different Assembly Processes

Carbon nanotubes are essential parts of the nanoelectronicsDevelopment of rational synthesis routes to multiply branched and interconnected low-defect nanotubes with targeted helicity would be a revolutionary advance for

nanoelectronics.

Applications

• Acting as wireBallistic current carrying: since nanotubes relay on ballistic current transfer so their current carrying densityis around 10 while for metals this value is around 10

No current-induced electromigration: at small scale when the conductive wires diameter become very smallthe current-induced electromigration causes interconnection between wires, but covalently bonded structure ofcarbon nanotubes prevent this problem.Problem of contact resistance: unfortunately, the ballistic current carrying capability is less useful for presently envisioned applications because of necessarily large contact resistances. Contacting all layers in a MWNT could reduce this contact resistance, but it cannot be totally eliminated.

Non-volatile memoryRef: T. Rueckes et al., Science 289, 94(2000).

SWNT four-terminal electronicsRef: M. S. Fuhrer et al., Science 288, 494 (2000).

Applications

• Nanotube-Field Effect Transistor (NT-FET)

Semiconducting nanotube: SWNT can behave like metalsor semiconductors based on their structure. We can usesemiconducting SWNT in FETs to make channel betweensource and drain. Fig.3.A and BMetal or Semiconductor: in the case of SWNT we cannotdetermine whether the proposed nanotube which has beenlocated between source and drain through random processor via AFM is semiconductor or not. This problem can besolved by reducing the walls of the MWNT to reach out theappropriate property. This technique seems applicable butstill not reliable and mass producible.Size problem: If we can solve the proposed problems butthere is still an unsolved problem which is the size of theNT-FETs. At 2002 (publishing year of this paper) FETs’ sizewere a few hundred of nanometers but nowadays, we havetransistors with 5nm channel length and so this problem isgoing to be solved.Integration: one of the important notes about NT-FETs istheir ability to be integrated.

Applications

• SensorsElectronic transport and thermopower: non-metallicnanotubes due to their electronic transport andthermopower (voltages between junctions caused byinter-junction temperature differences) are verysensitive to substances that affect the amount of theinjected charge.Low amount of sample: due to the small size ofnanotubes they require very little amount of sample fordetection.Major Challenges: these nano sensors should be able to differentiate between absorbed species in complex mixtures and provide rapid forward and reverse responses

• ProbesMechanical robustness and low buckling force:these two mechanical features are helping to increaseprobe lifetime and reduce sample damage.Cylindrical shape and small tube diameter: these two geometrical features lead to enable imaging in narrow, deep crevices and improve resolution in comparison to conventional nanoprobes, especially for high sample feature heights.Covalently modified nanotube tip: attaching molecules such as ligands to the nanotube can enable us to map the chemical and biological functions.Nanoscopic tweezer: through electrostatic interaction between two nanotubes on the probe we can make nanoscopic tweezer which can be used as the nanoprobes for assembly.

https://www.indiamart.com/proddetail/carbon-nanotube-based-afm-probe-14893761048.html

He, M; Croy, R. G.; Essignmann, J. M.; Swager, T. M.“Chemiresistive carbon nanotube sensors for N-nitrosodialkylamines.” ACS Sens. 2019, 4,

2819-2824.

Research Statistics in Nanotube Field

Thanks For Your Attention

Microsystems LaboratoryUC-Berkeley, ME Dept.

Electrochemical Energy Storage

1/29/2014

High energy density High power density

SupercapacitorsBatteriesFuel Cells Capacitors

1) D. Linden, T. Reddy, Handbook of Batteries,  McGraw ‐Hill, 2002.http://www.eng.fiu.edu/mme/Robotics/elib/RehargeableBatteries‐Paper‐MEI‐2012.pdf

85 Wh/kg(1)

0.05 kW/kg(1)

102 ‐103 cycles(1)

6 Wh/kg(2)

57 kW/kg(2)

106 cycles(2)

Cathode

Anode

Cathode

Electrolyte

Anode

Porous carbon (Electric Double Layer Capacitors)

Redox material (Pseudocapacitors)

2) Skeletontech, “SkelCap 2500, 4500, 3300, 4000” datasheet, December 2012.

Microsystems LaboratoryUC-Berkeley, ME Dept.

Carbon nanotubes (CNTs)

RuO2

Carbon nanotubes  (CNTs)

RuO2

1/29/2014

State of the Field

Pseudocapacitive Material High Surface‐Area Electrode

MnO2

Fe3O4

Conductive polymers

VOx

Activated carbon

Mesoporous carbon

Pseudocapacitors

Carbon aerogel*

2/24/2021 34

CNT-based Supercapacitor• Motivation• Micro Supercapacitor

— Stage 1: CNT forest electrodes— Stage 2: Functionalized CNT electrodes— Stage 3: Ultra-long CNT electrodes— Stage 4: Deeply-packed CNT electrodes

• Micro Battery• Summary

2/24/2021 35

Energy Storage Overview

•Regenerative brakes

•Camera Flash•Energy Buffer•Wireless Sensor Networks

2/24/2021 36

MEMS/Nano Battery

• Zinc-Air (UCLA) Electroplating, 10µm diameter, 200µm high

•Li-ion battery on Silicon, (Philips) DRIE, 1µm gap, 25µm Deep

•C-MEMS, (UCI), SU8 pyrolysis10µm diameter, 200µm high

•Si Nanowire, Li-ion battery, (Stanford), ~100nm diameter

2/24/2021 37

Motivation1. Miniaturization

2. Performance

•Audio Quality

•High Current

•Energy Storage

Supercapacitor

2/24/2021 38

SACd

©2011 University of California March 2011 Berkeley Sensor & Actuator Center

Spring 2011

I. Carbon Nanotube Forest Electrodes

MEMSSupercapacitor

EI E

SP

CC C dCV V

A

©2010 University of California Berkeley Sensor & Actuator Center 40/13

Aligned CNT Electrodes

2max

12

E CV

0 r SACd

Energy density

Power-like Network Tablet-like Network Vertical NetworkIon Diffusion Resistance Power density2

maxmax 4 s

VPR

4/14

©2011 University of California March 2011 Berkeley Sensor & Actuator Center

Spring 2011

CNT Growth on conductive substrates

5nm Fe as the catalyst for all the samples

2m

©2011 University of California March 2011 Berkeley Sensor & Actuator Center

Spring 2011

Fabrication process

1. Thermal oxidation

Silicon

SiO2

PRMetal layers

CNT

2. Lithography3. Deposit metal layers4. Lift-off5. CNT thermal CVD

growth6. Assembly

©2011 University of California March 2011 Berkeley Sensor & Actuator Center

Spring 2011

43

Supercapacitor electrodes using CNT Forests

100m 100m

100m 4m

h~80m

Uniform height

500m