Effect of thermal treatment on structure and properties of a-Si:H films obtained by cyclic deposition

The effect of thermal treatment in a vacuum on the structure and properties of amorphous hydrogenated silicon (a-Si:H) films obtained by cyclic deposition with intermediate annealing in hydrogen plasma was studied. a-Si:H films deposited under optimal conditions are characterized by the nonuniform distribution of the nanocrystalline phase (<1 vol %) across the film thickness and have the optical gap Eg=1.85 eV, the activation energy of conductivity Ea=0.91 eV, and a high photosensitivity (σph/σd≈107 under illumination of 100 mW/cm2 in the visible spectral range). Transmission electron microscopy studies demonstrated that thermal treatment in a vacuum leads to blurring of the initial layered structure of a-Si:H films and to a somewhat higher amount of nanocrystalline inclusions in the amorphous phase matrix. Thermal treatment above 350°C causes a dramatic increase in the dark conductivity, as well as the resulting decrease in the photosensitivity, of a-Si:H films.