Nanoscale thermoelectric properties of fs-laser induced nanotracks on Sb$_{2}$Te$_{3}$

Antimony telluride (Sb$_{2}$Te$_{3}$) is a canonical material for thermoelectric applications. It was recently shown that $\sim$20 nm diameter Sb$_{2}$Te$_{3}$ nanowires, fabricated by the vapor-liquid-solid method, exhibit $\sim$20{\%} enhancement in the Seebeck coefficient, S, in comparison to that of the bulk [1]. In addition, nanotrack formation was recently induced by fs-laser irradiation of Sb$_{2}$Te$_{3}$ [2]. Here, we report on the nanoscale thermoelectric properties of such fs-laser induced nanotracks on Sb$_{2}$Te$_{3}$ using scanning tunneling spectroscopy (STS) to probe the local density of states near the surface, and scanning thermoelectric microscopy (SThEM) to probe the local Seebeck coefficient just below the surface [3]. In the pristine (nanotrack) regions of Sb$_{2}$Te$_{3}$, STS reveals a bandgap of $\sim$0.3 eV (\textgreater 1 eV), suggesting the presence of an insulating surface layer in the irradiated regions. However, SThEM shows similar thermovoltages across both the pristine and nanotrack regions, presumably due to the buried regions of Sb$_{2}$Te$_{3}$. These data suggest that the nanotracks are buried beneath an insulating surface layer, consistent with our recent transmission electron microscopy observations. \\[4pt] [1] Y.M. Zuev, J.S. Lee, C. Galloy, H. Park, P. Kim, Nano Lett., \textbf{10}, 3037 (2010).\\[0pt] [2] Y. Li, V. A. Stoica, L. Endicott, G. Wang, H. Sun, K.P. Pipe, C. Uher, R. Clarke, Appl. Phys. Lett. \textbf{99}, 121903 (2011).\\[0pt] [3] J.C. Walrath, Y.H. Lin, K.P. Pipe, R.S. Goldman, Appl. Phys. Lett., in press (2013).