Growth study of chemical beam epitaxy of GaNxP1−x using NH3 and tertiarybutylphosphine
Abstract A study in the growth of GaN x P 1 − x epilayers by chemical beam epitaxy using tertiarybutylphosphine (TBP), ammonia (NH 3 ), and elemental Ga or triethylgallium is reported. Monitoring reflection high-energy electron diffraction (RHEED) intensity oscillations, we observe that both group-III- and group-V-induced incorporation rates are increased when NH 3 is introduced into a single cracker with TBP. From the difference in the periods of group-V-induced RHEED intensity oscillations, a 16% N incorporation is expected, but X-ray rocking curve measurement shows only 0.08% N. Using separate TBP and NH 3 crackers results in no enhancement in incorporation rates. We conclude that the cracking efficiency of TBP is increased with NH 3 co-injection.
N incorporation in GaNxP1 − x and InNxP1 − x using a RF N plasma source
N incorporation in GaN x P 1-x and InN x P 1-x using a RF N plasma source We report a study of N incorporation behavior into GaP and InP as a function of growth conditions. With increasing N2 flow-rate fraction (N 2 flow rate over total group-V gas flow rate), the N composition increases up to a point but then saturates. This might be due to the small solubility of N in these materials or the leveling off of the active N species at higher N 2 flow rate. At a fixed N 2 flow-rate fraction, the higher the growth temperature T s is, the less N can be incorporated, which results from the lowering of the sticking coefficient of nitrogen at higher T s . Although the general trend of the growth condition dependence is the same for N incorporation in InP and GaP, the amount of N that can be incorporated is quite different. With GaP, N as high as 16% can be obtained, while with InP, only less than 1% can be incorporated. This is considered to be due to the very high equilibrium vapor pressure of N2 over InN compared to that over GaN.
Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment
Abstract The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M6C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M6C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M6C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M6C carbides, which results in a decrease of the lattice parameter.