Thermoelectric devices allow one to recover electricity from waste heat, but current thermoelectric conversion efficiencies are below the level at which wide spread use becomes practical. However, nanowire arrays with diameters less than the thermal de Broglie wavelength are predicted to boost the efficiency of thermoelectric devices. A promising approach to produce nanowire arrays of such a small diameter (less than 10 nm) is electrochemical deposition within highly ordered nanoporous films formed by evaporation induced self-assembly of surfactants with metal oxide oligomers. However, key elements of our understanding of processing variables that control the formation of film topology remains elusive, in part due to the lack of characterization methods and analytical tools. Here, I will summarize my results on the development of grazing incidence small angle x-ray scattering (GISAXS) tools to quantitatively characterize highly-ordered nanostructured films,[1, 2] and show how we have used these tools to reveal a new understanding of how to control structure and topology of nanoporous films.[3-8] In particular we have developed a simple reproducible method to self-assemble highly ordered and oriented double-gyroid structure nanoporous films with facile mass transport.[4] This key advance enables these nanoporous films to be used to template 4 nm diameter nanowire arrays with high fill fraction. Finally, I will present results on the electrochemical deposition of bismuth telluride nanowire arrays within the nanoporous films and the development for use as nanostructured thermoelectric devices.[9]
REFERENCES
1. Tate, M. P.,* V. N. Urade, J. D. Kowalski, T. C. Wei, B. D. Hamilton, B. W. Eggiman and H. W. Hillhouse,* Simulation and Interpretation of 2D Diffraction Patterns from Self-Assembled Nanostructured Films at Arbitrary Angles of Incidence: from Grazing Incidence (above the critical angle) to Transmission Perpendicular to the Substrate, Journal of Physical Chemistry B, 110, pp. 9882-9892 (2006).
2. Tate, M. P.* and H. W. Hillhouse,* General Method for Simulation of 2D GISAXS Intensities for Any Nanostructured Film Based on a Discrete Fourier Transform: Implementation of the Distorted Wave Born Approximation, Journal of Physical Chemistry C, Articles ASAP, (2007).
3. Eggiman, B. W.,* M. P. Tate* and H. W. Hillhouse,* The Rhombohedral Structure of Highly Ordered and Oriented Self-Assembled Nanoporous Silica Thin Films, Chemistry of Materials, 18, pp. 723-730 (2006).
4. Urade, V. N., T.-C. Wei, M. P. Tate, J. D. Kowalski and H. W. Hillhouse, Nanofabrication of Double Gyroid Thin Films, Chemistry of Materials, 19, pp. 768-777 (2007).
5. Tate, M. P.,* B. W. Eggiman, J. D. Kowalski and H. W. Hillhouse,* Order and Orientation Control of Mesoporous Silica Films on Conducting Gold Substrates Formed by Dip-Coating and Self-Assembly: A Grazing Angle of Incidence Small-Angle X-ray Scattering and Field Emission Scanning Electron Microscopy Study, Langmuir, 21, pp. 10112-10118 (2005).
6. Tanaka, S., M. P. Tate, N. Nishiyama, K. Ueyama and H. W. Hillhouse, Structure of Mesoporous Silica Thin Films Prepared by Contacting PEO106-PPO70-PEO106 Films with Vaporized TEOS, Chemistry of Materials, 18, pp. 5461-5466 (2006).
7. Tate, M. P.,* C. M. Muzzillo and H. W. Hillhouse,* Mass Transport Rate Control During Spin Coating of Self-Assembled Films, Submitted, (2007).
8. Urade, V. N., L. Bollmann, J. D. Kowalski, M. P. Tate and H. W. Hillhouse,* Controlling Interfaction Curvature in Nanoporous Silica Films formed by Evaporation Induced Self-Assembly from Nonionic Surfactants: II Effect of Processing Parameters on Film Structure, Langmuir, 23, pp. 4268-4278 (2007).
9. Tate, M. P.* and H. W. Hillhouse,* 4 nm Nanowire Networks of Bismuth Telluride, Submitted, (2007).
* Indicates major and corresponding authors