Silicon Wafers Exhibiting Highly Surface-Related Thermoelectric Properties

Recognizing the facet-dependent electrical conductivity responses of silicon wafers should affect their thermoelectric properties, phosphorus-doped and intrinsic Si (110), (111) and (100) wafers were employed for electrical conductivity and thermal conductivity measurements. Particularly due to the large electrical conductivity differences, as well as considerable thermal conductivity variation, in these wafers, their room-temperature thermoelectric zT values can differ by an order of magnitude or more. X-ray diffraction (XRD) pattern analysis reveals lattice constant deviations in the wafers that cause these physical property changes, which also lead to large differences in their dielectric constants. Kelvin probe force microscopy (KPFM) also shows temperature-dependent surface potential and work function changes for the examined wafers. This work demonstrates that surface control or application of a pressure to introduce crystal lattice deviations can greatly tune a material’s transport properties.