Selective Deposition Of SiO2 Thin Films In Acid Baths

Author

M. A. Smith
L. L. Levenson, Missouri University of Science and Technology

Abstract

We report observation of deposition of SiO₂ thin films on a variety of surfaces in nitric acid and hydrochloric acid solutions. Scanning electron microscopy shows that the films are composed of closely packed spheres 1000 Å in diameter. Chemical identification is made with Auger electron spectroscopy. The films are generally between 1000 and 2000 Å thick and are possibly hydrated. Deposition occurs in either acid for molarities in the 1-8 M range and at temperatures between 80 and 100 °C. The effects for molarities greater than 8 M and temperatures greater than 100 °C have not been investigated. Materials on which the films form in nitric acid are tantalum, gold, silicon, niobium and Al₂O_3; in hydrochloric acid, films will form on tantalum, gold, silicon and Al₂O₃. Materials which are insoluble in the acids but upon which films have not been observed to form are graphite, platinum, chromium (nitric acid) and niobium (hydrochloric acid). Deposition occurs inside a sealed vessel made entirely of Pyrex-type glass. Vessels are partially filled with acid and are heated so that the upper glass surfaces (not in contact with the acid reservoir) are about 10-30 °C cooler than the reservoir. Acid vapors condense on the cooler glass surfaces forming droplets that run down the vessel walls to the reservoir. This process of acid flow on the walls leaches SiO₂ from the glass and increases the SiO₂ concentration in the reservoir until the SiO₂ films form. It is believed that a supersaturated condition is present during SiO₂ deposition. Experiments show that cessation of acid condensation halts film formation. Attack of the vessel provides the sole source of SiO₂. Preliminary kinetic measurements indicate that vessels must be heated for periods longer than 150 h before deposition occurs. Iron can be incorporated into the SiO₂ films by the dissolution of iron metal in the acid before sealing of the vessel. © 1982.

Recommended Citation

M. A. Smith and L. L. Levenson, "Selective Deposition Of SiO2 Thin Films In Acid Baths," Thin Solid Films, vol. 95, no. 2, pp. 161 - 166, Elsevier, Sep 1982.

The definitive version is available at https://doi.org/10.1016/0040-6090(82)90238-3

Department(s)

Physics

International Standard Serial Number (ISSN)

0040-6090

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2023 Elsevier, All rights reserved.

Publication Date

10 Sep 1982