Facet ridge end points in crystal shapes

Equilibrium crystal shapes (ECS) near facet ridge end points (FRE) are generically complex. We study the body-centered solid-on-solid model on a square lattice with an enhanced uniaxial interaction range to test the stability of the so-called stochastic FRE point where the model maps exactly onto one dimensional Kardar-Parisi-Zhang type growth and the local ECS is simple. The latter is unstable. The generic ECS contains first-order ridges extending into the rounded part of the ECS, where two rough orientations coexist and first-order faceted to rough boundaries terminating in Pokrovsky-Talapov type end points.Comment: Contains 4 pages, 5 eps figures. Uses RevTe

Non-universal equilibrium crystal shape results from sticky steps

The anisotropic surface free energy, Andreev surface free energy, and equilibrium crystal shape (ECS) z=z(x,y) are calculated numerically using a transfer matrix approach with the density matrix renormalization group (DMRG) method. The adopted surface model is a restricted solid-on-solid (RSOS) model with "sticky" steps, i.e., steps with a point-contact type attraction between them (p-RSOS model). By analyzing the results, we obtain a first-order shape transition on the ECS profile around the (111) facet; and on the curved surface near the (001) facet edge, we obtain shape exponents having values different from those of the universal Gruber-Mullins-Pokrovsky-Talapov (GMPT) class. In order to elucidate the origin of the non-universal shape exponents, we calculate the slope dependence of the mean step height of "step droplets" (bound states of steps) using the Monte Carlo method, where p=(dz/dx, dz/dy)$, and represents the thermal averag |p| dependence of , we derive a |p|-expanded expression for the non-universal surface free energy f_{eff}(p), which contains quadratic terms with respect to |p|. The first-order shape transition and the non-universal shape exponents obtained by the DMRG calculations are reproduced thermodynamically from the non-universal surface free energy f_{eff}(p).Comment: 31 pages, 21 figure

Thin Film Formation of Gallium Nitride Using Plasma-Sputter Deposition Technique

The formation of gallium nitride (GaN) thin film using plasma-sputter deposition technique has beenconfirmed. The GaN film deposited on a glass substrate at an optimum plasma condition has shown x-raydiffraction (XRD) peaks at angles corresponding to that of (002) and (101) reflections of GaN. The remainingmaterial on the sputtering target exhibited XRD reflections corresponding to that of bulk GaN powder. Toimprove the system’s base pressure, a new UHV compatible system is being developed to minimize theimpurities in residual gases during deposition. The sputtering target configuration was altered to allow themonitoring of target temperature using a molybdenum (Mo) holder, which is more stable against Gaamalgam formation than stainless steel

Radio-frequency MBE growth of cubic GaN on 3C-SiC(001)/Si(001) template

A 3C-SiC(001) was formed by coincidence site lattice matching on Si(001) through carbonization using acetylene (C 2 H 2 ) supplied by a jet nozzle. The 3C-SiC serves as a cubic template for the MBE growth of c-GaN on Si substrates. The Si substrate with lattice constant of a Si = 0.544 nm was covered with strained 3C-SiC whose lattice constant a 3C-SiC/Si = 0.445 nm expanded from that of the bulk 3C-SiC crystal (0.438 nm). Better quality cubic phase GaN film was grown on the strained 3C-SiC template layer when the Ga/N flux ratio approached unity of Ga rich side. The proportion of the cubic phase in the GaN layer was calculated to be 94.7% from the integrated intensity ratio of the X-ray diffraction peaks of c-Ga