Temperature Effects on the Electronic Conductivity of Carbon Nanotubes Mark Mascaro Department of Materials Science and Engineering Advisor Francesco Stellacci May 10, 2007

Dispersion and Functionalization of Nanotubes Nanotubes display unique electrical and mechanical properties, such as spectacular mechanical resilience and tunable conductivity, and are of interest as quantum wires, scanning probe tips, biosensors, and in many other applications. To use nanotubes in any system or device, it is necessary to achieve good dispersion or dissolution This can be achieved through purification techniques, surfactants, or chemical functionalization Chemical functionalization additionally provides a manipulable chemical handle, useful in controlling surface properties and designing self-assembly procedures Covalent chemical functionalization to the nanotube sidewall changes carbons from sp 2 to sp 3 hybridization, destroying electronic structure and conductivity

Carbene Functionalization Three bonding configurations O open is energetically preferred O open preserves sp 2 hybridization, and therefore conductivity Image from Lee and Marzari, Physical Review Letters 97:116801, 2007.

Electrode Fabrication 25 nm palladium electrodes Prepared by electron beam lithography (fingers) and optical lithography (pads) Large contact pad to accommodate destructive testing

Room-Temperature Resistance Measurements

Spread of many orders of magnitude in most samples Similarly-prepared samples show statistical dissimilarity, indicating uneven dispersion Tight spacing of resistance values in Carbene Prior, Pristine Prior, etc. indicates high nanotube density; implies significant resistance values

Multi-Pad Temperature Variation Measurements Samples containing several pads exhibiting approximately the ideal behavior were selected Sample brought to a certain temperature, multiple pads measured, then temperature adjusted again Plot of resistance against temperature for each sample shows no real behavior Contamination is a possibility Equilibration time is a possibility

Point-Dwell Test for Equilibration Predicted linear behavior is observed Random scattering of resistance values sampled immediately after chuck equilibration indicates sample likely equilibrates near-instantaneously

Single-Pad Temperature Variation Measurements: Carbene

Single-Pad Temperature Variation Measurements: Pristine

Single-Pad Temperature Variation Measurements: Nitrobenzene

Conclusions Carbene samples exhibit pristine-like behavior –Closely-spaced resistance values indicate a possible one-order difference –Similar temperature response –However, the precise difference cannot be quantified from this data alone This measurement technique is extremely sensitive to sample preparation –Dispersion cannot be measured or controlled for –Statistical methods were inconclusive: significant variation within identical samples made absolute comparison difficult –There is evidence of a contamination effect which permanently increases resistance in these samples upon temperature cycling

References Needs: 15, 17, 1. Jeffrey Bahr and James Tour. Covalent chemistry of single-wall carbon nanotubes. Journal of Materials Chemistry, 12:1952–1958, Sarbajit Banerjee, Tirandai Hemraj-Benny, and Stanislaus S Wong. Covalent surface chemistry of single-walled carbon nanotubes. Advanced Materials, 17:17-29, Robert Chen, Sarunya Bangsaruntip, Katerina Drouvalakis, Nadine Wong Shi Kam, Moonsub Shim, Yiming Li, Woong Kim, Paul Utz, and Hongjie Dai. Noncovalent functionalization of carbon nanotubes for highly specific electronic biosensors. Proc. Nat. Acad. Sci. USA, 100:4894, Y. Chen, R. C. Haddon, S. Fang, A. M. Rao, P. C. Eklund, W. H. Lee, E. C. Dickey, E. A. Grulke, J. C. Pendergrass, A. Chavan, B. E. Haley, and R. E. Smalley. Chemical attachment of organic functional groups to single-walled carbon nanotube material. Journal of Materials Research, 13(9): , Hongjie Dai. Carbon nanotubes: Synthesis, integration, and properties. Accounts of Chemical Research, 35: , Hongjie Dai, Jason H. Hafner, Andrew G. Rinzler, Daniel T. Colbert, and Richard E. Smalley. Nanotubes as nanoprobes in scanning probe microscopy. Nature, 384(6605): , Cees Dekker. Carbon nanotubes as molecular quantum wires. Physics Today, 52:22-28, Christopher A. Dyke and James M. Tour. Unbundled and highly functionalized carbon nanotubes from aqueous reactions. Nano Letters, 3(9): , Young-Su Lee and Nicola Marzari. Cycloaddition functionalizations to preserve or control the conductance of carbon nanotubes. Physical Review Letters, 97:116801, R. Saito, G. Dresselhaus, and M. S. Dresselhaus. Physical Properties of Carbon Nanotubes, Imperial College Press: London, Sander J. Tans, Michel H. Devoret, Hongjie Dai, Andreas Thess, Richard E. Smalley, L. J. Geerligs, and Cees Dekker. Individual single-wall carbon nanotubes as quantum wires. Nature, 386: , C. T. White and T. N. Todorov. Carbon nanotubes as long ballistic conductors. Nature, 393: , 1998.

AFM of Interdigitated Electrode