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Oxidation Mechanism of Si1_xGex Nanowires with Au Catalyst Tip as a Function of Ge Content
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- Authors
- Jung Min Bae, Kwang-Sik Jeong, Woo-Jung Lee, Min Baik, Jaehun Park, Mann-Ho Cho
- Issue Date
- 2017-10
- Citation
- ACS Applied Materials & Interfaces, v.9, no.42, pp.37411-37418
- ISSN
- 1944-8244
- Publisher
- American Chemical Society(ACS)
- Language
- English
- Type
- Journal Article
- Abstract
- Si1-xGex nanowires (NWs) (0.22 ?돞 x ?돞 0.78) were synthesized using a vapor-liquid-solid procedure with a Au catalyst. We measured the intrinsic physical, chemical, and electrical properties of the oxidized Si1-xGex NWs using several techniques, including transmission electron microscopy, X-ray photoemission spectroscopy, and optical pump-THz probe spectroscopy. We suggest two distinct oxidation mechanisms depending on the Ge content in the Si1-xGex NWs: (i) when the Ge content is around 0.22, a Au catalytic effect brings about oxidation in both the axial and lateral directions; and (ii) when the Ge content is greater than 0.22, the Au tip is detached from the NW body and does not act as a catalyst, which is a result of the high degree of Ge-atom participation in the oxidation process. Additionally, we measured the photoconductivity decay time distribution for the Si1-xGex NWs before and after oxidation process; the decay time is significantly shortened in oxidized Si1-xGex NWs (0.22 < x), whereas it is maintained for Si-rich Si1-xGex NWs (x ≈ 0.22) as compared to the as-grown Si1-xGex NWs. It indicates that the number of defect states is generated with the formation of defective Ge oxide at the oxide-shell-layer/Si1-xGex-core-NW interface.
- KSP Keywords
- As-grown, Au catalyst, Axial and lateral, Decay time, Electrical properties, Electron microscopy(SEM), Ge content, High degree, Photoconductivity decay, Transmission Electron Microscopy(TEM), X-Ray photoemission spectroscopy(XPS)