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Thermodynamics of oxidation and reduction during the growth of metal catalyzed silicon nanowires

Nebol'sin, Valery A.; Johansson, Jonas LU ; Suyatin, Dmitry B. LU and Spiridonov, Boris A. (2019) In Journal of Crystal Growth 505. p.52-58
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... (More)

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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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
A1. Growth models, A1. Nanostructures, A1. Surface processes, B2. Semiconducting IV materials
in
Journal of Crystal Growth
volume
505
pages
7 pages
publisher
Elsevier
external identifiers
  • scopus:85054455219
ISSN
0022-0248
DOI
10.1016/j.jcrysgro.2018.10.001
language
English
LU publication?
yes
id
d338993c-6044-4b02-9c95-40a828c7f0ab
date added to LUP
2018-10-26 13:26:56
date last changed
2018-10-26 13:26:56
@article{d338993c-6044-4b02-9c95-40a828c7f0ab,
  abstract     = {<p>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 O<sub>2</sub>, and under favorable kinetic conditions Si NWs should entirely convert into dioxide (SiO<sub>2</sub>). Thermal dissociation of SiO<sub>2</sub> in the growth conditions for NWs is practically impossible as it would require either lowering the pressure of O<sub>2</sub> 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 O<sub>2</sub> and this O<sub>2</sub> 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 O<sub>2</sub> 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 SiO<sub>2</sub>. Only metals with a lower affinity to O<sub>2</sub> than to H<sub>2</sub> or any other reducing agent are applicable to guarantee the recovery process when used as a catalyst for the growth of NWs.</p>},
  author       = {Nebol'sin, Valery A. and Johansson, Jonas and Suyatin, Dmitry B. and Spiridonov, Boris A.},
  issn         = {0022-0248},
  keyword      = {A1. Growth models,A1. Nanostructures,A1. Surface processes,B2. Semiconducting IV materials},
  language     = {eng},
  pages        = {52--58},
  publisher    = {Elsevier},
  series       = {Journal of Crystal Growth},
  title        = {Thermodynamics of oxidation and reduction during the growth of metal catalyzed silicon nanowires},
  url          = {http://dx.doi.org/10.1016/j.jcrysgro.2018.10.001},
  volume       = {505},
  year         = {2019},
}