Ordered Electronic Reconstruction of the (1120) ZnO Single Crystal

Abstract

Three-dimensional (3D) charge-written periodic peak and valley nanoarray surfaces are fabricated on a (112 over bar 0$11\bar{2}0$) ZnO single crystal grown via chemical vapor transport. Because the grown ZnO crystals exhibit uniform n-type conduction, 3D periodic nanoarray patterns are formed via oxygen annealing. These periodically decorated structures show that the peak arrays are conducting at the nanoampere level, whereas the valley arrays are less conductive. Energy dispersive spectroscopy indicates that the valley arrays are deficient in zinc by approximate to 4-6 at%, and that the peak arrays are deficient in oxygen, respectively. Kelvin probe force microscopy reveals the presence of periodic wiggles featuring variations of approximate to 70-140-meV between the peak and valley arrays. A significant decrease in the Fermi level of the valley region is observed (approximate to 190 meV), which corresponds to a high zinc vacancy doping density of 2 x 10(18) cm(-3). This result indicates the periodic generation of an extremely large electric field (approximate to 11 000 V cm(-1)) in the vicinity of the peak-valley arrays. Computational analysis corroborates the experimentally observed generation of V-Zn and the preferential formation of surface protrusions on ZnO (112 over bar 0$11\bar{2}0$) rather than on (0001), based on surface effects, along with the generation of peak and valley features.