| Thermoelectric (TE) materials have been widely investigated and used in a variety of systems such as solid-state coolers, infrared detectors, and power generators. Integration of TE thin films in micro-scale systems offers advantages such as integration, size, and weight for many new applications. In order to provide design flexibility for thermoelectric microsystems, high-quality TE thin films with good adhesion and uniformity are needed on a variety of substrates. Motivated by the applications of TE materials in microsystems, the goal of this dissertation is to explore the technology and characterization of co-evaporated high quality (Bi,Sb)Te-based thin films on various substrates.;Thermal evaporation is an attractive thin film deposition technique because of its relative simplicity, reproducibility, ease of process control, and high throughput. Characterization techniques are applied to a variety of TE films in order to enhance physical understanding of the effects of deposition conditions, substrate material/crystallinity, and substrate preparation on film properties. This dissertation shows that the grain size, composition, and TE properties of thin films depend strongly on the co-evaporation process conditions including substrate material, deposition substrate temperature, and elemental flux ratio. Our results show that maximum power factors are achieved on Poly-Si and Kapton® substrates at Tsub= 270 °C for n-type Bi2Te 3 films, and on oxide and poly-Si substrates at Tsub= 250°C for p-type Sb2Te3 films. The optimum (Bi,Sb)Te-based binary films have tellurium atomic percentage of about 60%.;This work moves beyond co-evaporation of binary alloys towards advanced thermoelectric films of ternary alloys. It demonstrates co-evaporation as a low-cost process for the deposition of telluride-based ternary films for the first time.;One of the main challenges in devices using TE thin films compared to bulk material is the increasing importance of contact resistance. Contact resistance can cause major degradation in TE microsystems performance. In this dissertation, test structures are introduced with novel material-shape combinations for minimization of electrical contact resistivity between (Bi,Sb)Te-based thin films and various contact metals. Characterization of resistivity based on the contact material, physical structure, and surface treatment facilitates control and reduction of electrical contact resistance. |
