Theoretical study of the influence of temperature on SrO, BaO and TiO₂ growth and adsorption on GaN (0001) surface

The dynamics simulates of adsorption process of SrO, BaO and TiO₂ molecules on GaN (0001) surfaces at 300, 400, 500, 600 and 700℃ are studied by Ab initio molecular dynamics methods based on the first principles. The influences of temperature on the energies of system, dynamic trajectories, Mulliken charge populations, surface bonding electron density distributions (ELF) and diffusion coefficients in the adsorption process are discussed. Under different temperatures, the bonding time of O-Ga, the bonding atoms of O and Ga in SrO, the bonding order of O atom and Ga atom in TiO₂ are different. The temperature also has a significant effect on the final adsorption state and orientation of SrO, BaO and TiO₂ adsorption on GaN (0001) surface. In addition, the effects of temperature on adsorption energy of different adsorption systems are not the same. The order of preferential adsorption for small molecules in GaN (0001) substrate surface are successively TiO₂, SrO and BaO molecules. The higher the temperature is, the sooner the bonding time, the shorter the bond length under normal circumstances. The data analysis shows that the optimal growth temperatures of SrO and BaO are 600℃, but that of TiO₂ is 500℃. (authors)