Abstract
The silicon network of the ‘‘device-quality’’ hydrogenated amorphous silicon (a-Si:H) fabricated by a glow-discharge method has been studied by means of Raman spectroscopy, infrared spectroscopy, and mechanical stress measurements. Attention has been focused on the variation of the network structure induced by the change in fabrication conditions. An increase in the substrate temperature results in a shift of the TO peak in the Raman spectra toward a high wave number, an increase in the compressive mechanical stress, and a decrease in the hydrogen content in a-Si:H. It is found that the hydrogen content of the monohydride configuration (CHm) has a positive correlation with the compressive stress in a-Si:H, and the hydrogen content of the dihydride configuration (CHd) has the opposite correlation. It is also found that the position of the TO peak (ωTO) shifts toward a low wave number as the CHm increases, and that the ωTO shifts toward a high wave number when an external compressive stress is applied to a-Si:H. The experimental results suggest that the shift of the TO peak in the Raman spectra originates from the change in the force constant of Si–Si bonds induced by hydrogen atoms of a monohydride configuration in the silicon network. Variations of the silicon network caused by the change in substrate materials are also discussed.
Published Version
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