ICT2014 Abstracts

Group 15 chalcogenides M₂E₃ (M = Bi, Sb; E = Te, Se) and their solid solutions are important room temperature thermoelectric materials. It has been demonstrated that nanostructuring of these materials can lead to an increase in thermoelectric efficiency.¹ We present a new and versatile methodology for the deposition of highly oriented crystalline thin films, micron- and nano-scale patterned arrays and individually positioned nanocrystals of Bi₂Te₃ and Sb₂Te₃.

Chemical vapour deposition (CVD) is a low cost and scalable technique for the deposition of thin semiconductor films, though it often requires toxic gases as precursors. A safer and more convenient method may be to use a single molecular precursor which contains the required elements.² We have designed and synthesised such precursors for the CVD of group 15 chalcogenides, which were employed to deposit high quality thin films of M₂E₃ onto SiO₂ and TiN substrates using low pressure CVD at 450-500 °C. Films were characterised by X-ray diffraction, SEM, EDX and Raman spectroscopy, demonstrating that they were composed of single phase, highly <0 0 1> axis oriented hexagonal crystallites with a 2:3 ratio of M:E and very low impurity levels. Hall and Seebeck coefficient measurements of the thin films demonstrate that they have comparable electronic and thermoelectric properties to M₂E₃ thin films deposited by other methods.

Using lithographically patterned substrates, which exploit selectivity of deposition onto TiN over SiO₂, these materials can be confined precisely to micron-scale or nano-scale areas, creating a patterned array; in wells of below 200 nm single crystals selectively deposit into each well, with <1 1 0> axis orientation, whereas larger wells contain polycrystalline, <0 0 1> oriented films.

1. C. J. Vineis, A. Shakouri, A. Majumdar, M. G. Kanatzidis, Adv. Mater., 2010, 22, 3970-3980.

2. M. A. Malik, M. Afzaal, P. O’Brien, Chem. Rev., 2010, 110, 4417-4446.