Optical absorption edge in structure-inhomogeneous a-Si:H-based alloys |
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| Institution: | 1. Department of Material Science, Moscow Institute of Electronic Technology, kor.405, kv.208 Zelenograd, K-498, Moscow 103498, Russian Federation;2. Delft University of Technology, Felmannweg 17, P.O. Box 5053, 2600, GB Delft, The Netherlands;1. Baskin School of Engineering, University of California, Santa Cruz, CA, USA;2. Nanostructured Energy Conversion Technology and Research (NECTAR), Advanced Studies Laboratories, University of California, Santa Cruz, and NASA Ames Research Center, Moffett Field, CA, USA;1. Department of Energy Systems Research and Department of Materials Science and Engineering, Ajou University, Suwon 16499, South Korea;2. Samsung Advanced Institute of Technology, Suwon 16674, South Korea;3. School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, South Korea;4. National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom;5. Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 34141, South Korea;6. Ames Laboratory, Ames, IA 50011, United States;1. Department of Materials Engineering, Federal University of Rio Grande do Norte, 59078-970, Natal, RN, Brazil;2. Department of Physics and Chemistry, School of Natural Sciences and Engineering, São Paulo State Universtiy (UNESP), 15385-000, Ilha Solteira, Brazil;3. Modeling and Molecular Simulation Group, São Paulo State University, 17033-360, Bauru, SP, Brazil;1. Chitkara University Institute of Engineering and Technology, Chitkara University, Punjab, India;2. Government Degree College, Sarkaghat, H.P. 175024, India |
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| Abstract: | In this paper we measure microstructure and optical absorption edge of a-Si:H and silicon-rich a-SiNr:H films prepared at deposition rates ∼0.8 nm/s by radio frequency plasma enhanced chemical vapor deposition method from hydrogen diluted SiH4 and SiH4 + NH3 mixtures, respectively. Microstructure of films was studied by atomic force microscopy and infrared spectroscopy. Both a-Si:H and a-SiNr:H films are inhomogeneous on a scale of ∼50 nm and contain Si-rich islands with hydrogen (in a-Si:H) or hydrogen and nitrogen (in a-SiNr:H) collected at their boundaries. It was found that different atomic configurations of N and H determined from IR data should be attributed to such islands and their boundaries. It was established that the optical gap is determined by the concentration of hydrogen (in a-Si:H) or nitrogen (in a-SiNr:H) in the islands while it is insensitive to variations of content of these alloy atoms at island boundaries. These results are interpreted in terms of a quantum well model modified to take into account structure of alloy atoms. |
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