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Temperature effects on the properties of Ge thin films

The effects of substrate temperature (T-s) on the properties of vacuum evaporated p-type Ge thin films have been investigated for 25 < T-s < 400 degrees C. Increase in the substrate temperature improves the crystallinity and increases the grain size resulting a gradual change from amorphous to polycrystalline structure which was attained above a substrate temperature of 225 degrees C. Low resistive (1 x 10(-2) ohm-cm) and high mobility (280 cm(2)/V . s) films were obtained at T-s = 400 degrees C. It has been observed that the conduction mechanism in polycrystalline films was dominated successively by hopping, tunneling and thermionic emission as the sample temperature was increased from 40 to 400 K. In amorphous samples, conduction was described in terms of different hopping mechanisms. (C) 1999 Kluwer Academic Publishers.