Decomposition, Oxidation, and Hydrolysis Kinetics of Monobutyltintrichloride

Due to its electrical, optical, and mechanical properties, tin oxide coatings can be found in a wide range of applications. Fluorine doped tin oxides are transparent for visible light, highly reflective for infrared radiation, and may have a sheet resistance down to 3 Ω/square. These thin films are used in architectural windows for reflecting heat [1], in solar cells for carrying the cell’s current without blocking sun light [2], in wear resistive coatings on glass bottles [3], and in gas sensors [4]. The most common method for producing tin oxide coatings on glass is chemical vapour deposition (CVD). Although a wide variety of precursors can be used, one of the most commonly used is monobutyltintrichloride (MBTC). Tin oxide deposition from mixtures of MBTC, oxygen, and water vapor is a difficult process to optimize and control; low conversion efficiencies are often observed and good film uniformity can be difficult to obtain. Chemical reactions in the gas phase are known to be important, even rate controlling, in some tin oxide deposition processes. Consequently, the chemistry and kinetics of MBTC thermal decomposition, oxidation, and hydrolysis reactions in the gas phase is a critical element in model development. This paper focuses on analysing the gasphase reactions occurring during deposition of tin oxide. The experiments are performed in a reactor system in which concentration and temperature distributions can be neglected, thus allowing analysis of the intrinsic chemical kinetics.