Charles M. LieberHarvard University

Nanowires: A Platform for Nanoscience & Nanotechnology

http://cmliris.harvard.edu

Lieber Research GroupBrian TimkoPing XieJian-Ru GongTzahi Cohen-KarniLu WangDidier Cassanova

Quan QingBozhi TianThomas KempaHwan Sung ChoeSirui ZouYizhe Zhang

Hao YanYongjie HuGuihua YuYajie DongXiaocheng JiangQuihua Xiong

Xiaolin ZhengYing Fang Xuan GaoYat LiHong-Gyu Park Won-Il ParkJie Xiang

Ritesh AgarwalWei LuAli JaveyFernando PatolskySilvija GradecakAlex Wong Pavle RadovanovicChen Yang Mike McAlpineYue Wu

Outline of PresentationNanowire Platform Functional Nanowire DevicesNanoelectronic-Biology InterfaceConclusions

Nanowires as a Platform

Synthetic control of structure and composition on many length scales Predictable and tunable electronic properties allow fundamental limits of nanodevices/1-dimensional systems to be addressedNanowires with controlled chemical and electronic properties represent an ideal building block for exploring new functional devices and hybrid materials. Nanoscale wires/nanowires are of central importance to integrated nanosystems

Exploit to answer what is possible!

Si/Au phase diagram

Wagner, Whisker Technology, (Wiley, New York 1970) p. 47

AuSi(ls) + Si(s)

History: Key Growth Concepts

AuSi(ls)

r

rmin = 2σLVVL /RTlnσ~ 100 nm

σLV is liquid-vapor interfacial free energyVL is the liquid molar volumeσ is the vapor phase supersaturation Wagner & Ellis, Appl. Phys. Lett. 4, 89 (1964)

Nanowires: A General & Predictable Approach

Breaking symmetry for 1D growth. Nanoscale wires can be prepared rationally by exploiting a catalyst to direct preferentially the addition of reactant.

supersaturation/nucleation

growth

termination

reactor hot zoneThe key issue for controlled nanowire growth is the generation of nanometer scale ‘catalyst’ clusters.

The growth process begins when the catalyst becomes supersaturated with reactant, and terminates when the nanowires pass out of the hot reaction zone.

Morales & Lieber, Science 279, 208 (1998)Hu, Odom & Lieber, Acc. Chem. Res. 32, 435 (1999)

Nanowires: A General & Predictable Approach

Breaking symmetry for 1D growth. Nanoscale wires can be prepared rationally by exploiting a catalyst to direct preferentially the addition of reactant.

supersaturation/nucleation

growth

termination

reactor hot zoneThe key issue for controlled nanowire growth is the generation of nanometer scale ‘catalyst’ clusters.

The growth process begins when the catalyst becomes supersaturated with reactant, and terminates when the nanowires pass out of the hot reaction zone.

Morales & Lieber, Science 279, 208 (1998)Hu, Odom & Lieber, Acc. Chem. Res. 32, 435 (1999)

Nanocluster-Catalyzed Nanowire Growth: An Early Summary

minimum diameters ~3 nm with single crystal structurescontrolled nucleation yields monodisperse diameters with controlled lengthssurface properties tailed for assembly and device properties

Material Group IV Group IVAlloys:

III-V III-V Alloys II-VI

SiGe

SixGe1-x GaAsGaPGaNInAsInP

GaAsxP1-x

InAsxP1-x

ZnSZnSeCdS

CdSe

GrowthConditions

330-1200Fe, Ni, Au

850-950Fe, Au

700-1000Cu, Ag, Au

800-950Au, Ag

700-1000Au

Composition pure 1:1 defined bystarting

composition

1:1

Duan & Lieber, Adv. Mat. 12, 298 (2000)

How Perfect are Nanowires?Low-temperature transport provides measure of ‘impurity and defect-free’ length scale.

S DVgate

Constraints for observing quantized charge transport:

1. Charging energy U=e2/C > kBT

2. ( )Ω≈>> kehRt 262( )( ) hCRCetE t >=ΔΔ 2

Vsd

I

Vsd

dI/dVsd

Vg

dI/dVsd

Vg

V sd

Tilke, etc. JAP, 89, 8159, 2001

Single Electron Tunneling in Silicon Nanowires

Regular period for coulomb charging peaks consistent with single charge tunneling through one quantum structure with discrete energy levels.Transport through single quantum structures is observed for nanowire lengths up to at least 400 nm, ca. 10x longer than in any nanofabricated silicon.

Impurities or defects that perturb electronic transport must be separated on length scale >400 nm!

T = 4.2 KL = 400 nm

Zhong, Fang, Lu & Lieber, Nano Lett.5, 1143 (2005)

Nanowire Heterostructures & Superlattices

1-d growth nucleation

axial growth

axial heterojunction/superlattice

Gudiksen, Lauhon, Wang, Smith & Lieber, Nature 415, 617 (2002)

Lauhon, Gudiksen, Wang & Lieber, Nature 420, 57 (2002)

radial growth

axial growth

radial heterostructures

Germanium/Silicon Core/Shell Nanostructures

Lu, Xiang, Timko, Wu & Lieber, PNAS 102, 10046 (2005)

Core/shell nanowire structure enablesControl of surface defects and statesDesign of carrier gases confined in uniform 1D potentialReduced scattering and correspondingly achieve higher mobility transistors as well as enable new studies of quantum phenomena at low-temperatures!

5nm

Si

Ge

Pushing Nanowire Transistor Limits

Transconductance = 26 μS/VMax Ion= 35 μAScaled values (Vdd=1V; 70/30 on/off):

Gm = 1.4 mS/μmIon = 0.78 mA/μm

Transconductance = 60 μS/VMax Ion= 91 μA. Scaled values (Vdd=1V; 70/30 on/off):

Gm = 3.3 mS/μmIon = 2.1 mA/μm

Xiang, Lu, & Lieber, Nature 441, 489 (2006)

First demonstration that a nanowire transistor could exceed limits of top-down devices!

Nanowire FETs: How Good Are They?

Transconductance = 182 μS/VMax Ion= 152 μAScaled values (Vdd=0.5V; 70/30 on/off):

Gm = 5.0 mS/μmIon = 1.7 mA/μm

S = 160 mV/decade

L= 40 nm, 8x faster than Si p-MOSFET, and shows fundamental limit > 2 THzIon is ~100% of the ballistic limit at low bias

Hu, Lieber & coworkers, Nano Lett. 8, 925 (2008)Xiang, Lu, & Lieber, Nature 441, 489 (2006)

Fully control of interdot coupling and barrier height by local top gatesPlunger gates control charge numberDouble dot capacitively coupled to sensor dot on adjacent nanowireCharge sensing critical for single-electron double dots and spin control

Double Quantum Dot with Integrated Charge Sensor Based on Ge/Si Nanowires

Hu, Churchill, Lieber & Marcus, Nature Nano. 2, 622-625 (2007)

T = 100 mK

T = 100 mK

Integrated Charge Sensors and Fast Manipulation

• scaled dot size defined by lithography• two charge sensors on same nanowire allows readout of double dot charge state• two RF gates allow fast (~1ns) manipulation of double dot

NW

60

55

50

45

40

V R (m

V)

400395390385380VL (mV)

-30-25-20-15-10-5

current (10-12A

)

Ic0c1_1380

bias=-0.2 mV10 MHz

60

55

50

45

40

V R (m

V)

400395390385380VL (mV)

-60-50-40-30-20-100 current (10

-12A)

Ic0c1_1381

bias=-0.2 mVno RF pulses

honeycomb (no pulses):

square wave on VL and VRRF in

Core/Shell Architecture & Photovoltaics: What is possible and what can we learn?

p-type/intrinsic/n-type (p-i-n) core/shell/shell silicon nanowires in which the structure and composition of the core and shells are readily controlled. Radial structures might enable improved carrier collection and overall efficiency, comparable to single crystal semiconductors,while retaining solution processing of nanoparticle and organic systems.

Tian, Zheng, Kempa, Lieber & coworkers: Nature 449, 885 (2007)

p-i-n Core/Shell Nanowire Properties

Dark current-voltage (I-V) data demonstrate (i) ohmic contacts and (ii) good rectifying/diode behavior with quality factors, n, of ~2.Under 1-sun illumination, yield an open circuit voltage of 0.260 V, a short circuit current (density) of 0.503 nA (24 mA/cm2), and stable operation of at least 8-months!1-sun efficiency, ~3.5%, and current density exceed values achieved with nanoparticle & nanorod composite systems, although open circuit voltage is lower.Power output is ~ 1 nW (ca. 100 W/m2)

Tian, Zheng, Kempa, Lieber & coworkers: Nature 449, 885 (2007)

Axial & Coaxial p-i-n Nanowire Platforms for Photovoltaics

Optical absorption and transport characteristics are unique compared to radial core/shell nanowires. Important point of comparison for studies of carrier generation, recombination and collection at the nanometer scale.

Axial p-i-n Nanowires: Synthesis & Properties

Controlled modulation of p-, i-, and n-type diode regionsEtching delineates different doped Si regions

Kempa, Tian, Lieber & coworkers, Nano Lett. 8, 3456 (2008)

Good quality diodes (not Schottky) with quality factors for i = 4um of 1.2-1.3.∆Isc is proportional to ∆ilength implies that photocurrent is predominantly from i-region

Exploring Novel Nanostructure To Push Limits of Photovoltaic Efficiency

Controlled synthesis enables integration of ≥2 p-i-n diodes in series with independent control of junctions.Substantial increase in open circuit voltage realized in ‘tandem’ axial single nanowire photovoltaic elements!

Qian, Lieber & coworkers, Nature Mater. 7, 701 (2008)

I. Tandem Solar Cells

II. MQW Solar Cells

Kempa, Tian, Lieber & coworkers, Nano Lett. 8, 3456 (2008)

Individual coaxial nanowires function as robust photovoltaic devices with sufficient power output to drive nanoelectronic devices ‘on chip’.A single photovoltaic nanowire integrated with a nanowire sensors is capable of powering the nanowire sensor device without external input.

Tian, Zheng, Kempa, Lieber & coworkers: Nature 449, 885 (2007)

Assembly of Multi-Functional Structures: NW-Photovoltaic Powered Nanodevices

Interfaces between nanoelectronic & biological systems

Natural length-scale for electronic interfaces

Nanoelectronic-Biological Systems

Create new tools for biophysics to healthcare

Hybrid materials that enable new opportunities in science & technology

Nanoelectronic – Biology Interface

Requirements:Nanoscale devices – the right size (stuff)Reproducible and tunable electronic properties Controlled and predictable bio-surface propertiesUnconventional fabrication to enable flexible and transparent substrates and/or 3D structures

⇒⇒ Nanowires

Nanowire Nanosensors: Beginning

A nanotransistor is transformed into a nanosensor by modifying the surface with a receptor.Changes in the surface charge ‘gate’the device and yield a conductance change.

Cui, Wei, Park & Lieber, Science 293,1289 (2001)

+ streptavidin(25 pM)

buffer

Detection of Proteins

Real-time label-free High-sensitivity and specificity

Nanosensor Chip for Real-Time, Label-Free Multiplexed Detection

Bottom-up/top-down hybrid fabrication yields large number of addressable nanowire elementsAssemble distinct types of nanowires on single chipPersonalize sensor elements with distinct receptors

Cui, Wei, Park & Lieber: Science 293,1289 (2001)Patolsky, Zheng, Lieber et al., PNAS 101, 14017 (2004)Patolsky, Zheng & Lieber, Nature Protocols 1, 1711 (2006)

Buffer

Multiplexed Cancer Marker Detection

1500

1600

1700

1800

1900

2000

2100

2200

0 2000 4000 6000 8000

Time / s

a

b

c

d

ef

PSA

CEA

MUC

Multiplexed, real-time monitoring of cancer marker proteins.Quantitative & selective detection of protein concentration to femtomolar level.General platform for multiplexed, ultrasensitive, real-time detection of proteins and other species!

1.4 pg/ml

2 pg/ml

Zheng, Patolsky & Lieber, Nat. Biotech. 23, 1294 (2005)

Undiluted Blood Serum Analysis

Serum samples are characterized after single step ‘desalting’purification. (1) buffer; (2) Donkey Serum (DS),59 mg/ml total protein; (3) DS + 2.5 pM PSA; (4) DS + 25 pM PSA

(1) DS + 0.9 pg/ml; (2) DS

Zheng, Patolsky & Lieber, Nat. Biotech. 23, 1294 (2005)

Marker proteins are detected selectively in presence of ca. 100-billion-fold excess of serum proteins!

• Vista combines nanowire devices and biotechnology to provide all the tools needed to measure biomarkers over time.

• Revolutionize monitoring of biomarkers of therapeutic response and toxicity in the clinic and lab for drug development through patient care.

Making Good on the Promise: Commercialization

Vista Therapeutics, Inc.www.vistatherapeutics.org

Ultimate Sensor: Single-Particle Detection

Can nanoscience enable detection at ultimate limit of a single biological entity?

Patolsky, Zheng, Lieber et al., PNAS 101, 14017 (2004)

Single-Particle Detection: How Small?

Can the sensitivity of nanowire sensors be pushed to enable true single molecule detection?Consider the case of small oligonucleotides:

Fang, Zheng, Tian, Yan, Zhou & Lieber

Nanoelectronic-Cell/Tissue Interfaces

Neurons+

Nanosensors

Nanowire nanoelectronic devices can enable:Interface to cells at natural scale of biological communicationInput/output of electrical signalsInput/output of chemical/biological signals

An example:

Nanowire/Neuron Junctions

NW1 NW2

NW3 NW4

axon

IC

IC Stimulation

NW1 Stimulation

Nanowire (NW) response correlated w/conventional measurementsMultiplexed recording with flexible arrays is straight forwardNanowire/neuron junctions can be localized at level of individual neurites

Patolsky, Timko, Lieber & coworkers, Science 313, 1100 (2006)

Nondestructive, Real-time Neurotransmitter Detection

X. Jiang, L. Wang, S. Zou & Lieber

Selective detection of neurotransmitter dopamine to at least 100 fM sensitivity Reversible & nondestructivePotential for high spatial and temporal resolutionPotential for simultaneous neurotransmitter & action potential recording

General Approaches for Building & Using Nanoelectronic Tools?

Nanowire-Heart Interfaces: Pushing the Limits

Timko, Cohen-Karni, Yu & Lieber

Flexible and transparent chips enable simultaneous electrical recording and optical imaging in 3D configurations not accessible with traditional planar technologies!Enables electrical recording with simultaneous optical registration down to cellular level with opaque tissue/organ samplesStarting point for implants, “smart” engineered tissue, and functional biomaterials.

Interfacing to Brain Slices

S. Pal & V. MurthyQ. Qing, B. Tian, & Lieber

Vision for Life SciencesNanoelectronic-Biological Interfaces Enable:

Diagnostic devices for disease detectionGeneral detection & kinetics platform New tool for single-molecule detection/biophysicsPowerful devices for electronic and chem/bio recording from cells, tissue & organsPotential implants for highly functional & powerful prosthetics, as well as hybrid biomaterials enabling new opportunities

Nanoelectronic-Biological Interfaces

ConclusionsSynthetic control of nanowire structure and composition demonstrated at level beyond other nanomaterials.Nanowire structural and compositional diversity exploited to push limits of conventional and quantum electronic devices, as well as to explore new device concepts, such as for solar energy conversion.Nanowire nanoelectronic devices demonstrated as broad tools for life sciences, from ultrasensitive detection to electrically-sensitive recording from cells and tissue with potential for novel interfaces for prosthetics.