engleski

Raman study of "boson peak" in amorphous silicon: Dependence on hydrogen and carbon content

A systematic Raman study of dependence of ."boson peak" on hydrogen and carbon content in amorphous silicon thin films is presented. With increasing the hydrogen content the spectral form of the "boson peak" changes while its intensity remains constant. The opposite be­ haviour was observed with increasing the carbon content. These observations were interpreted in the frame of fractal model. The temperature reduced Raman spectra were decomposed on to phonon­ fracton curve and Gaussian shaped bands by fitting procedure. The increase of intensity of the "boson peak" (fractal component) with carbon content is qualitatively interpreted with appearence of nanometer-strained fractal regions which origin should be in homogeneous substitutional bonding of carbon atoms in a-Si network. The observed increase of fractal correlation length with hydrogen content is explained with reduction of internal strain influenced by hydrogen bonding. These findings were confirmed by Auger spectroscopy and atomic force microscopy at high magnifica­ tions where the homogeneous distribution of carbon atoms and nanometer-sized blobs of silicon atoms were observed.

Raman study

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