We develop a simple reaction model for the liquid-solid phase transition in the context of the lattice Boltzmann method with enhanced collisions. Calculations for a two-dimensional test problem of Ga melting and for a two-dimensional anisotropic growth of dendrites are presented and commented on.

Homoepitaxial (100) β-Ga₂O₃ films were grown on substrates with miscut angles of 2°, 4°, and 6° toward [00$\overline{1}$ ] by metal organic vapor phase epitaxy. Step-flow growth mode, resulting in smooth film surfaces and high crystalline quality, could only be achieved if the diffusion length on the film surface corresponds approximately to the width of the terraces. Otherwise, 2D islands or step-bunching is obtained, which results in a deteriorated crystalline quality and reduced Hall mobility of the electrons. By varying the growth parameters such as the O₂/Ga ratio, Ar push gas flow, and chamber pressure, the diffusion length could be adjusted so that step-flow growth mode could be achieved at all miscut angles. Furthermore, the growth rate could remarkably be increased from 1.6 nm/min to 4.3 nm/min. For homoepitaxial β-Ga₂O₃ films grown in step-flow growth mode, TEM measurements revealed a high crystalline quality, which is correlated with a high Hall mobility of 131 cm²/V s at a carrier concentration of 1.6 × 10¹⁷cm⁻³, which is comparable with β-Ga₂O₃ single crystal bulk values. This study clearly points out the high potential of β-Ga₂O₃ films for high performance MOSFETs if the influence of the deposition parameters on the structural and electrical properties is well understood.

A phase-field lattice kinetic model is presented for the numerical simulation of the dendritic growth of a pure crystal in the presence of thermal transport. A finite-difference scheme for the phase field is combined with an explicit lattice kinetic scheme for the temperature field. The resulting scheme is advanced in time with an adaptive time-marching procedure which permits us to achieve long simulation times with larger time steps than explicit finite-difference and previous kinetic methods. The method is demonstrated for the case of dendritic growth of a single crystal over a wide range of Stefan and capillarity numbers.

We present a comprehensive density functional theory study addressing the adsorption, dissociation, and successive diffusion of water molecules on the two regular terminations of SrTiO3(001). Combining the obtained supercell-geometry converged energetics within a first-principles thermodynamics framework we are able to reproduce the experimentally observed hydroxylation of the SrO-termination already at lowest background humidity, whereas the TiO2-termination stays free of water molecules in the regime of low water partial pressures. This different behavior is traced back to the effortless formation of energetically very favorable hydroxyl-pairs on the prior termination. Contrary to the prevalent understanding our calculations indicate that at low coverages also the less water-affine TiO2-termination can readily decompose water, with the often described molecular state only stabilized toward higher coverages.