A theoretical investigation of photoluminescence spectra for amorphous silicon quantum-dots (1 - 4 nm), at room temperature, were used to study the effect of both spatial and quantum confinements spontaneously via determination the energy peak of maximum intensity transition. The results show a continuous shifting toward low energy peak (red shift) and toward high-energy peak (blue shift), with the decreasing of quantum dot size, due to spatial and quantum confinements respectively. These results have leaded us to believe that such quantum dot size (1 nm) changes the nature of amorphous silicon optical band gap from indirect to direct transition material.
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