Optical modeling of iridium thin film erosion under oxygen plasma exposure

Abstract

This work is motivated by interest in use of iridium metal films in the space environment. Optical metrology is a sensitive tool for study of film roughness, optical constants, and microstructural properties. In the present paper, in situ spectroscopic ellipsometry is applied to monitor oxygen plasma etching of films of iridium/chromium on fused silica substrates, using an electron cyclotron resonance plasma source. Optical modeling allows for a fundamental understanding of the plasma etching mechanism. Analysis of spectroscopic psi and delta data at selected time slices suggests the iridium film is etched away gradually upon plasma irradiation, while showing no signs of oxidation or other chemical changes. Nanoscale atomic mixing and index of refraction grading are observed.

Effect of ion assistance parameters on the properties of Ir coatings

“…The complex of Ir properties opens up wide opportunities for the use of bulk materials and thin coatings in high-tech fields of science and technology. Such materials are used to protect rocket engine nozzles [2], in tools for the production of high-quality glasses [3], crucibles [4], heavy metal ion sensors [5], microelectronics [6,7], medicine [8], mirrors of X-ray telescopes [9], and elements of optical systems of spacecraft [10]. Thin Ir layers are used as an effective barrier to prevent the diffusion of carbon [11] and oxygen [12].…”

Oxidation of double glow plasma discharge coatings of iridium on molybdenum for liquid fuelled rocket motor casings

“…1,2 Iridium (Ir) has a high melting point of 2443uC, low vapour pressure at 2000uC and greatly superior oxidation and corrosion resistance compared with Mo above 1000uC. 3,4 Ir coatings have been considered as promising candidate materials for protection of carbon and refractory metals at ultra high temperatures. 5,6 Thus, to prevent the combustion and increase the service life of Mo nozzles, an Ir coating would be a potential candidate.…”

“…However, Mo oxidises significantly above 300-500°C and combusts at temperatures in excess of 1800-1900°C, typical of direct flame impingement 1 1,2. Iridium (Ir) has a high melting point of 2443°C, low vapour pressure at 2000°C and greatly superior oxidation and corrosion resistance compared with Mo above 1000°C 3 3,4. Ir coatings have been considered as promising candidate materials for protection of carbon and refractory metals at ultra high temperatures 5 5,6.…”