| AVS 59th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM+SS+AS+NS-ThM |
| Session: | Nanoelectronic Interfaces, Materials, and Devices |
| Presenter: | J.C. Walrath, University of Michigan |
| Authors: | J.C. Walrath, University of Michigan Y.H. Lin, University of Michigan K.P. Pipe, University of Michigan R.S. Goldman, University of Michigan |
| Correspondent: | Click to Email |
Thermoelectric (TE) devices allow reliable solid-state conversion of heat to electricity. The efficiency of a TE device is determined by the figure of merit, ZT, which is sensitive to the Seebeck coefficient, S. Traditional S measurements are used to quantify thermally-induced electron transport on a macroscopic scale. A promising alternative method for nanoscale measurements of S is scanning thermoelectric microscopy (SThEM). In SThEM, an unheated scanning tunneling microscopy (STM) tip acts as a high-resolution voltmeter to measure the thermally-induced voltage, V, induced by a temperature gradient in a heated sample. SThEM has been utilized to measure V across a GaAs p-n junction [1], with the spatial profile of S determined through a comparison of the measured V with a simulation of a network of resistors and voltage sources, based upon a theoretical S-value [2]. Although this approach is useful for predicting the measured V, it does not provide a method for direct conversion of the measured V to a local S. We have developed a Fourier heat conduction model to calculate a temperature profile matrix, thereby enabling direct conversion between the measured V and the local S. According to our model, SThEM can be optimized by fine-tuning several parameters, including the cone angle of the STM tip and the relative thermal conductivity of the tip and sample. We applied our model to SThEM data across a GaAs p-n junction [1] and improved the agreement between the measured and theoretical S by 40%. Our progress towards SThEM measurements of CoSb3 and InAs quantum dots will also be discussed. This material is based upon work supported by the Department of Energy under Award Number DE-PI0000012. Y.H. Lin and R.S. Goldman are supported in part by DOE under contract No. DE-FG02-06ER46339.
[1] H.K. Lyeo, A.A. Khajetoorians, L. Shi, K.P. Pipe, R.J. Ram, A. Shakouri, and C. K. Shih, Science 303, 816 (2004).
[2] Z. Bian, A. Shakouri, L. Shi, H.K. Lyeo and C.K. Shih, Appl. Phys. Lett. 87, 053115 (2005)