Papers by Keyword: MOCVD Process

Abstract: A modified large-size MOCVD reactor is developed to produce uniform and large-volume epitaxy thin film layer of gallium nitride (GaN). The full governing equations for continuity, momentum, energy and chemical species are solved numerically. It is investigated how thermal flow field, and the operating parameters affect molar concentration of each reactant, and the thin film uniformity. These parameters are involved such as the chamber pressure (100-700 torr), susceptor rotation rate (100-800). In this paper, the simulation results from these listed parameters shows that an optimum epitaxy layer can be achieved in the large-size reactor.

Abstract: Erbium oxide (Er₂O₃) was shown to be a high potential candidate for tritium penetration barrier and electrical insulator coating for advanced breeding blanket systems such as liquid Li, Li-Pb or molten-salt blankets. Recently, Hishinuma et. al. succeeded to form Er₂O₃ coating layer on large interior surface area of metal pipe using Metal Organic Chemical Vapor Deposition (MOCVD) process. In this work, Er₂O₃ coating layer of hydrogen penetration control on stainless steel 316 (SUS 316) substrate have been investigated to the effect of hydrogen penetration and using SEM, TEM and SAED patterns. Er₂O₃ coating layer of before hydrogen penetration was granular structures from SEM observation. Er₂O₃ coating layer was columnar grains from TEM observation. TEM image and SAED patterns obtained from Er oxide film can be understood that the growth direction of Er₂O₃ film was [110].

Abstract: Present work investigates the wear resistance of SAE 52100 steel coated with nanocoating Al2O3 by the Metal-organic Chemical Vapor Deposition (MOCVD) process. The wear tests by sliding and abrasion were performed in a ball-on-disc apparatus whose ball substrate was SAE 52100 steel. The MOCVD nanocoating processes were carried out in a research laboratory apparatus at 240oC under N2 + O2+ H2O atmosphere. The counterface discs were ABNT 1008 steel sheet used in the Brazilian fridge industry. The wear resistance of the nanocoated steel spheres were evaluated through the ball-on-disc test, using a sliding velocity 0.6 m/s, normal loads of 20 N and 30 N, total sliding distance up to 2400 m and controlled conditions of temperature and humidity at 25oC and 42% respectively. The balls material substrates were submitted to two distinct coating procedures: direct Al2O3 film deposition on substrate, or phosphatizing and then Al2O3 deposition via MOCVD. The discs were tested as received. From the plotted graphs of cumulative lost volume versus sliding distance, lower wear rates were observed for the nanocoated SAE 52100 sphere compared to the sphere without coating, i.e., nanocoating with Al2O3 increases the sphere wear resistance. This is probably due to a reasonable film adhesion. The balls phosphatized and coated with Al2O3 showed similar wear resistance but a spherical micro-grain film of Al2O3 . The wear mechanisms were also examined by scanning electron microscopy.

Abstract: CaCu3Ti4O12 (CCTO) thin films have been successfully deposited by Metal Organic Chemical Vapor Deposition (MOCVD) technique. A novel approach based on a molten multicomponent precursor source has been applied. The molten mixture consists of the Ca(hfa)2•tetraglyme, Ti(tmhd)2(O-iPr)2, and Cu(tmhd)2 [Hhfa= 1,1,1,5,5,5-hexafluoro-2,4- pentanedione; tetraglyme= 2,5,8,11,14-pentaoxapentadecane; Htmhd= 2,2,6,6-tetramethyl-3,5- heptandione; O-iPr= iso-propoxide] precursors. Film complete structural and morphological characterizations have been carried out using several techniques [X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM)].