Theoretical investigation on the structural properties of ZnO grown on sapphire

Abstract

We have investigated the growth mechanisms of ZnO on the c-plane sapphire(0001) substrates by the first-principles calculation. The first-principles total energy calculations of a sapphire slab with an isolated zinc adatom and an isolated oxygen adatom explain the experimental results such that the in-plane alignment between the ZnO and the sapphire is [10-10]ZnO//[11-20] sapphire. Moreover, from the experimental and theoretical results of GaN/sapphire growth mechanisms, the change of the polarity is very important for the migration barrier energy. The relative total energies for the isolated zinc adatom on the sapphire(0001) surface is very small while that for the isolated oxygen adatom on the sapphire(0001) surface is very large. When analogizing these relative energies with the experimental and theoretical results of GaN/sapphire growth mechanisms, we expect that the polarity of grown ZnO film on the sapphire substrate is the O-polarity. And the polarity of the direct growth of ZnO on the sapphire (0001) substrate does not change from the O-polarity under any growth conditions without using the low-temperature amorphous ZnO buffer layer. [DOI: 10.1380/ejssnt.2006.544]