Self-assembled growth and luminescence of crystalline Si/SiOx core-shell nanowires.
Crystalline Si/SiOx core/shell nanowires (NWs) are self-assembled by annealing Ni-coated hydrogenated Si-rich SiOx (SRO:H) films at 1100 degrees C in the presence of Si powder. Plasma-enhanced chemical vapor deposition is used to grow 100 nm SRO:H thin films with varying silicon concentration (n(Si)). The NWs vary from SiOx nanowires to Si/SiOx core/shell structures depending on the composition of the SRO:H substrate, with the fraction of core/shell structures increasing with increasing Si concentration. As n(Si) increases from 37 to 43 at.%, the average diameter of the NWs also increases from 48 to 157 nm. A growth model based on the diffusion-assisted vapor-liquid-solid mechanism is proposed to explain how the core/shell structures are self-assembled. Photoluminescence (PL) spectra of the individual NWs have two major emission bands in the near UV (381 nm) and blue (423 nm) ranges at n(Si) = 43 at.%, named as UV and BL PL bands, respectively. In contrast, only the BL PL band is observed at n(Si) < or = 39 at.%. These results suggest that the BL and UV PL bands can be attributed to the defect states in the SiOx shell and at the Si core/SiOx shell interface, respectively, and that the BL band is closely related to the growth process of the NWs.
Kim
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Department of Applied Physics, College of Applied Science, Kyung Hee University, Yongin 446-701, Korea.
Kim
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Shin
D H
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Hong
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Kim
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Kim
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Choi
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SH
Kim
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Elliman
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Kim
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D003460:Crystallization; D004058:Diffusion; D008027:Light; D049449:Luminescence; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission / Q000379:methods; D049329:Nanostructures; D036103:Nanotechnology / Q000379:methods*; D053770:Nanowires / Q000737:chemistry*; D011208:Powders; D012825:Silicon / Q000737:chemistry*; D013696:Temperature; D014466:Ultraviolet Rays
D011208:Powders; D012825:Silicon