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Atomic Force microscopy is an important tool to study the atomic structure and electronic properties of the surface and has been extensively used to study the growth process, surface evolution, surface morphology and grain size of thin films. The technique has been used to detect the light induced structural changes in amorphous silicon films by measuring the change in surface roughness of these films before and after exposure to light. In a carefully designed experiment, the amorphous silicon films deposited on glass substrates are exposed to light through the substrate using an optical fiber. In this geometry, neither the sample nor the AFM probe is disturbed during light soaking. Several surface scans were recorded before and after light soaking and an statistical average of surface roughness in each state is taken. It has been observed that rms surface roughness increases significantly after exposure to light. The changes in surface topography and rms roughness are evidence of light induced structural changes in these films, which are otherwise difficult to detect. The experiment provides a direct way to understand the causes of light induced metastability in hydrogenated amorphous silicon thin films. Details of the experiment and the results will be presented at the conference. |