Vertical Self-Defined Thermoelectric Legs for Use in Thin-Film μTEGs

Abstract:

Micro-thermoelectric generators (µTEGs) directly produce electrical power using temperature gradients available in the environment. Containing no moving parts, they are small, robust and well suited for emerging WSN and IoT applications. In particular, thin-film based µTEGs are desirable due to their cost and scalability advantages. However, the film-thickness constraints inherent to thin-film processes limit their potential usage. In order to maintain a temperature difference across the generator, the thermoelectric material must be thick for sufficient thermal resistance. This work establishes a new µTEG design to eliminate the thermal shorting issue. In the presented design, thermoelectric elements are formed on the sidewall of an array of high aspect-ratio pillars. This decouples the film thickness from the height of the thermoelectric allowing high thermal resistances with film thickness of less than two microns. Key to this design is the development of N-Bi2Te3/P-Sb2Te3 thermoelectric films grown over vertical surfaces. Additionally, thermocouple formation, and integration of the structure into functional µTEGs are also detailed.