The formation mechanism of the core-shell structure of a BaTiO3(BT)–MgO–Ho2O3-based system was studied. Mg reacted with BT at low temperatures and showed poor diffusivity compared with Ho. The core-shell structure was considered to be formed by the suppression of the diffusion of Ho into the core region by Mg. Also, replacement modes of Mg and Ho in perovskite were investigated. Lattice parameters were determined at temperatures higher than the Curie temperature in order to avoid crystal structure change. It was confirmed that Mg dissolved in Ti site, and Ho dissolved in both Ba and Ti sites. This indicates that Mg ions act as acceptors and Ho ions act as both donors and acceptors in the shell phase.
A quick cleaning process was developed for a silicon carbide chemical vapor deposition reactor. For this purpose, the stability of the susceptor coating film made of pyrolytic carbon was evaluated by means of exposing it to 100% chlorine trifluoride gas for 10 min at various temperatures. The original surface morphology of the pyrolytic carbon film was maintained under 480 • C. The fluorine atoms incorporated into the pyrolytic carbon film were removed by annealing at 900 • C either in ambient hydrogen or in ambient nitrogen. Finally, the 30-μm thick silicon carbide film formed on the pyrolytic carbon was successfully cleaned by the chlorine trifluoride gas either at 400 • C for 30 min or at 460 • C for 15 min and by additional annealing in ambient nitrogen at 900 • Chemical vapor deposition (CVD) 1-5 is one of the most frequently used techniques for producing advanced materials. It consists of two processes, such as film deposition and cleaning. The cleaning process is necessary for removing the unnecessary film formed on the susceptor and various reactor parts other than the substrate, because such films very often emit small particles. In order to maintain a clean condition for the deposition, a cleaning process has been implemented in the CVD for producing various materials, except for silicon carbide.The semiconductor silicon carbide (SiC) film is produced by means of the CVD process. 3-5 For realizing high efficiency power devices, silicon carbide has suitable properties, 6 such as a wide bandgap, high electron mobility, high thermal conduction, and high chemical and mechanical stabilities. However, these significant chemical and mechanical stabilities often cause practical problems, particularly for the CVD reactor cleaning. Currently, the silicon carbide CVD reactor does not have a cleaning process, because the convenient non-plasma reactor cleaning gases, such as hydrogen chloride, cannot react with silicon carbide. 7 Thus, a new reactor cleaning gas and cleaning process need to be developed.For this purpose, the authors have developed the in situ silicon carbide CVD reactor cleaning process using chlorine trifluoride (ClF 3 ) gas. [8][9][10][11][12] Previous studies [8][9][10] have shown that the chlorine trifluoride gas could remove the various types of silicon carbide films formed on the silicon-carbide-coated carbon susceptor in spite of operating for a significantly long time, such as 1-2 hours. This very long time was unfortunately necessary, because the cleaning temperature must be kept low for suppressing any etching damage to the susceptor coating film made of silicon carbide. However, recently and fortunately, the pyrolytic carbon film has been found to have a very low etching rate by the chlorine trifluoride gas. 12 Thus, the combination of the chlorine trifluoride gas and the pyrolytic carbon coating film should be studied in detail for achieving a quick cleaning process which is applicable for industrial production.As an extension of our previous study, 12 this study evaluated the temperat...
In order to develop a cleaning process for the silicon carbide chemical vapor deposition reactor, the susceptor coating materials are developed for protecting the susceptor from the etching by chlorine trifluoride gas. The chlorine trifluoride gas does not give a serious damage to the pyrolitic carbon film at the temperatures lower than 480 °C, at which temperature the quick and practical reactor cleaning process is expected to be possible
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.