Time-resolved Optical Properties of SiNW Oriented in <211> Crystallographic Direction
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.267
Time-resolved Optical Properties of SiNW Oriented in Crystallographic Direction Fatima1, Aaron Forde2, Talgat M. Inerbaev3,4, Nuri Oncel5, and Dmitri S. Kilin1 1 Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, USA
2 Department of Materials Science and Nanotechnology, North Dakota State University, Fargo, North Dakota 58102, United States
3
Sobolev Institute of Geology and Mineralogy, SB RAS, Novosibirsk, 630090, Russian Federation
4
L.N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan
5
Department of Physics & Astrophysics, University of North Dakota, Grand Forks, North Dakota 58202, USA
ABSTRACT:
Silicon nanowires (SiNWs) show unique optoelectronic properties such as band gap, radiative and nonradiative relaxations. In this research, the optoelectronic properties of SiNW are calculated by combining time-dependent density matrix methodology. Description of photo-excited dynamics processes is enabled by computing “on–the–fly” nonadiabatic couplings (NAC) between electronic and nuclear degrees of freedom using density functional theory (DFT). The dynamics of electronic degrees of freedom is propagated by the reduced density matrix with Redfield equation of motion. Oscillator strengths are used to compute radiative relaxation and to generate time resolved photoluminescence (PL) spectrum. Analysis of the simulated nonradiative decay shows that high-energy photoexcitation relaxes to the band gap edge on the order of 1 ps. We also simulate time-resolved emission spectra of the SiNW that reveals optical emissions above the optical band gap. These emission features are attributed to the interband transitions. The results of this study can be useful for the material choice for optoelectronic applications.
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INTRODUCTION Today the most important semiconductor material for the optoelectronics and photovoltaics industries is crystalline silicon (c-Si). This prominent position follows from unique properties such as the availability of large single crystals, high purity, effective conductivity engineering, and natural abundance. Because of indirect bandgap of c-Si, the optical properties are poor and does not show efficient emission and absorption of light [1]. Si nanostructures offer strong optical properties originating from quantum confinement. Silicon nanowires (SiNWs) represent a unique and special class of nanomaterials because of their intrinsic properties such as one dimensionality, high surface-to-volume ratio, and biocompatibility [2]. The development of SiNWs provides compatibility with existing silicon-based technology [3]. Several methods for fabricating SiNWs have been reported including the vapour–liquid– solid (VLS) method
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