| 2. |
- Nebol'sin, Valery A., et al.
(författare)
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Thermodynamics of oxidation and reduction during the growth of metal catalyzed silicon nanowires
- 2019
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 505, s. 52-58
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the thermodynamics of oxide formation, and the recovery of silicon and the metal catalysts from the dissociation of their respective oxides during the growth process of Si nanowires (NWs) under the Vapor → Liquid Droplet → Solid (VLS) mechanism. It is demonstrated that Si NWs under growth temperatures are thermodynamically unstable in any gas phase containing even a small concentration of O2, and under favorable kinetic conditions Si NWs should entirely convert into dioxide (SiO2). Thermal dissociation of SiO2 in the growth conditions for NWs is practically impossible as it would require either lowering the pressure of O2 to an unachievable, critically low value or raising the temperature to a point which is impossible to reach in ordinary conditions. Decreasing the diameter, i.e., increasing the Si NW dispersity, leads to an increase in the interaction with O2 and this O2 will be held more tightly by Si. Thus, thinner NWs should oxidize stronger than thicker ones. The main metal catalysts for NW growth, as well as Si, are characterized by significant affinity with O2 and inconvertible oxide formation reactions. The most stable Si NW growth is observed with metals (Au, Pt, Cu, Ni, etc.) whose oxides are less stable than SiO2. Only metals with a lower affinity to O2 than to H2 or any other reducing agent are applicable to guarantee the recovery process when used as a catalyst for the growth of NWs.
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| 3. |
- Karchevskii, E., et al.
(författare)
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Determination of permittivity from propagation constant measurements in optical fibers
- 2015
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Ingår i: Springer Proceedings in Mathematics and Statistics: 3rd Annual Workshop on Inverse Problems, 2013, Stockholm, Sweden, 2-6 May 2013. - Cham : Springer International Publishing. - 2194-1009 .- 2194-1017. - 9783319124988 ; 120, s. 55-65
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Konferensbidrag (refereegranskat)abstract
- We present a new method for determination of dielectric permittivity constant using measurements of fundamental mode of propagation constant in optical fiber’s. We first solve the forward spectral problem to compute the dispersion curve for the fundamental mode. Then using this curve we present an effective and accurate spline-collocation method for calculation of permittivity.
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