Growth mechanism of ZnO deposited by nitrogen mediated crystallization

We investigate the growth mechanism of ZnO deposited by a nitrogen mediated crystallization (NMC) method. NMC is a method in which nitrogen is used to control nucleation via a nitrogen adsorption-desorption behavior. The growth of NMC-ZnO is classified into three stages, that is, the pre-nucleation stage, nucleation and grain growth stage for 4-30 nm in thickness, and coalescence stage for 31-100 nm in thickness. NMC-ZnO nucleation takes place in a very short period compared to that for conventional ZnO. Hence, NMC-ZnO has a uniform grain size distribution, flat surface with less spiky grains, and a longer lateral correlation length of the surface, leading to a larger grain size than in conventional ZnO. Utilizing this NMC-ZnO as a buffer layer, low resistive aluminum doped zinc oxide ZnO:Al (AZO) films are obtained at the buffer layer film thickness ranging from 4 to 30 nm. The lowest resistivity is 3.4 × 10^-4Ωcm for 90 nm thick AZO deposited on NMC-ZnO buffer layers of 10 and 30 nm in thickness.