Quantum well films have the potential to more than double the efficiency of thermoelectric devices used to convert waste heat into electricity. Quantum well films consist of many very thin alternating ceramic layers, each approximately 100Å thick, deposited on a
suitable substrate (typically Si). Unfortunately, the substrate, which is needed for mechanical support, can act as a thermal short. This can be overcome by maximizing the ratio of film thickness to substrate thickness. This project will fabricate very thick (>10m ) quantum well films on a very thin Si substrate (~5µ) leading to very efficient and stable power generation devices. Phase I demonstrated outstanding performance of multilayer boron carbine films for thermoelectric energy conversion. Individual films were found to have a figure-of-merit that was on order of magnitude greater than the bulk material. Combinations of these multilayer boron carbide materials were paired with multilayer Si/SiGe or bulk bismuth telluride, and a conversion efficiency of up to 24 percent was measured. The main focus in Phase II will be on increasing the ratio of multilayer film to substrate, by a progressive approach to thicker films and thinner substrates. Deposition and annealing process conditions will be selected to allow this increase without the build-up of unacceptable stress. Device structures will be built and tested.