Structure and thermoelectric properties of boron doped nanocrystalline Si0.8Ge0.2 thin film

The structure and thermoelectric properties of boron doped nanocrystalline Si0.8Ge0.2 thin films are investigated for potential application in microthermoelectric devices. Nanocrystalline Si0.8Ge0.2 thin films are grown by low-pressure chemical vapor deposition on a sandwich of Si3N4∕SiO2∕Si3N4 films deposited on a Si (100) substrate. The Si0.8Ge0.2 film is doped with boron by ion implantation. The structure of the thin film is studied by means of atomic force microscopy, x-ray diffraction, and transmission electron microscopy. It is found that the film has column-shaped crystal grains ∼100nm in diameter oriented along the thickness of the film. The electrical conductivity and Seebeck coefficient are measured in the temperature range between 80–300 and 130–300K, respectively. The thermal conductivity is measured at room temperature by a 3ω method. As compared with bulk silicon-germanium and microcrystalline film alloys of nearly the same Si∕Ge ratio and doping concentrations, the Si0.8Ge0.2 nanocrystallin...

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