The deposition of Bi2Te3 and Sb2Te3 thermoelectric thin-films by thermal co-evaporation and applications in energy harvesting

Abstract

Bismuth, antimony and tellurium compounds (Bi/Sb/Te) are known as the best thermoelectric materials for room temperature operation. Despite thermoelectric devices with these materials being used for many years in macro-scale dimensions (millimetres sized devices), only few attempts were done to reduce these devices to the micro-scale (micrometers sized devices). The deposition of thermoelectric films was reported before using techniques like electrochemical deposition (ECD), metal-organic chemical vapour deposition (MOCVD), pulsed laser deposition (PLD), sputtering and thermal evaporation [1-8]. Each technique has its vantages and disadvantages, and a summary can be found in the table 5.1. In this table, CVD and ECD present opposite characteristics: While CVD films present high figure of merit (ZT), but a low deposition rate and expensive and complicated equipment is required (specific gases are needed for the deposition), ECD is a simple process, allowing high deposition rates (tens of μm can be achieved) but resultant films present low ZT. However, ECD allows the creation of structures during the deposition process, using the LIGA process (from German “Lithographie, Galvanoformung, Abformung”, meaning Lithography, Electroplating and Molding). In this chapter, the deposition of Bi2Te3 and Sb2Te3 thin films by thermal co-evaporation is described.