Temperature dependence of semiconducting and structural properties of Cr-Si thin films

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Abstract
Electrical and structural properties of coevaporated Cr‐Si thin alloy films and bilayer Cr/Si films as a function of annealing temperature from 10 to 1000 °K have been studied by in situ electrical resistivity and Hall measurements, and structural analysis including MeV 4He+ ion backscattering, x‐ray diffraction, Auger electron spectroscopy combined with Ar sputtering, electron microprobe, and scanning and transmission electron microscopy. In the as‐deposited state, the coevaporated alloy film was amorphous. Upon annealing, a sharp increase in resistivity occurred near 270 °C and the increase has been determined to be amorphous to crystalline CrSi2 phase transformation. The resistivity increased further with annealing up to 550 °C then a gradual decrease took place beyond 600 °C. In cooling, the resistivity increased monotonically with decreasing temperature. For the bilayer Cr/Si films, the annealing behavior is similar except the sharp increase in resistivity occurred around 450 °C due to the formation of CrSi2. The crystalline CrSi2 has been determined to be a semiconductor with an energy gap of 0.27 eV. It is p‐type, having a hole concentration of 4×1019 cm−3 at room temperature and a hole mobility of 7.2×104×T (temp)−3/2 cm2/V sec in the acoustic scattering region. The kinetics of amorphous‐to‐crystalline transformation of Cr‐Si alloy film in the temperature range of 225–25 °C has been determined to follow a t7 (time) dependence with an apparent activation energy of 1.13 eV.