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Room temperature synthesis of porous SiO 2 thin films by plasma enhanced chemical vapor deposition
| Content Provider | Semantic Scholar |
|---|---|
| Author | Barranco, Angel Cotrino, José Yubero, Francisco Espinós, Juan P. González-Elipea, A. R. |
| Copyright Year | 2017 |
| Abstract | Silicon dioxide thin films with variable and controlled porosity have been prepared at room temperature by plasma enhanced chemical vapor deposition in an electron cyclotron resonance microwave reactor with a downstream configuration. The procedure consists of the deposition of successive cycles consisting of a sacrificial organic-polymeric layer and, afterward, a silicon dioxide layer. Toluene and oxygen are used as precursors of the organic layers and Si(CH 3)3Cl and oxygen for the SiO2 . During deposition of the latter, the organic layer is simultaneously burned off. In these conditions, the release of gases produced by oxidation of the organic-polymeric layer take place while the oxide layer is being deposited. Thus, modification of the nucleation and growing mechanism of the silicon oxide thin film take place. The porosity of the final porous SiO 2 thin films increases with the thickness of the sacrificial organic layer. The porous SiO 2 films prepared with the aforementioned method are free of carbon and chlorine contamination as confirmed by Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. Depending on their porosity, the SiO 2 th n films are either transparent or scattered visible light. The former have refractive index lower than that of thermal silicon dioxide and the latter show membranelike behavior in gas diffusion experiments. All the samples have good adhesion to the substrates used for the deposition, either polished Si wafer, glass plates, or standard porous supports. They have columnar microstructure, as determined by scanning electron microscopy. A preliminary ultraviolet-visible characterization of the optically transparent thin films reveals that transmission of light through glass increases by 7%–8% when the porous silica is deposited on this substrate. These films prove to be very efficient as antireflective coatings and are of interest for photovoltaic and similar applications. It is possible to deposit SiO 2 thin films with densities as low as 0.65 g/cm 3 ~corresponding to a porosity of 70% ! by adjusting the thickness of the sacrificial and SiO2 layers. The films with high porosity are promising materials for the fabrication and/or modification of diffusion membranes. The gas adsorption properties and the type of porosity of the SiO2 thin films are assessed by adsorption isotherms of toluene at room temperature measured with a quartz crystal monitor device. The gas permeation properties of the films ~when used as membranes ! are analyzed by studying the diffusion rate of different gases through them. © 2004 American Vacuum Society. @DOI: 10.1116/1.1761072 # |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://idus.us.es/xmlui/bitstream/handle/11441/63465/Room%20temperature.pdf?isAllowed=y&sequence=1 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
