Light and thermally induced metastabilities in electrochemically etched nanocrystalline porous silicon |
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| Authors: | NP Mandal M Awasthi A Konar A Kumar DN Patel |
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| Institution: | 1. Department of Physics , Indian Institute of Technology , Kanpur, 208016, India niriiitk@gmail.com;3. Humboldt-Universit?t zu Berlin, Institut für Physik , AG Moderne Optik, Hausvogteiplatz 5-7, D-10117 Berlin, Germany;4. Department of Physics and Department of Electrical Engineering , University of Notre Dame , Notre Dame, IN 46556, USA;5. Department of Physics and Applied Physics , University of Massachusetts Lowell, 1 University Avenue , Lowell, MA 01854, USA;6. Department of Physics , Indian Institute of Technology , Kanpur, 208016, India |
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| Abstract: | We observe that light soaking for short durations and thermal quenching in nanocrystalline porous silicon (PS) produce metastable states. These metastable states show higher dark and photo currents, large photoluminescence and a weaker electron spin resonance (ESR) signal. However, long exposures to light produce the opposite effect. The metastable states are stable against sub-band gap light exposures. These metastable states can be removed by annealing at 150°C for 1 h. ESR shows the presence of a-Si phase (g ～ 2.0058, 6.4 G) in PS sample, but it is not sufficient to explain all the experimental results. Rather, our experiments suggest that light soaking causes more than one type of defects in porous silicon. The structural changes involving the movement of hydrogen present at the surface of PS or at the PS/a-Si interface may be responsible for these effects. |
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