Hexagonal Tubular Electrical Properties Of Zno Thin Films

Zinc Oxide(ZnO) is a very important semiconductor with a wide band gap, which possesses good optical, photoelectrical, and electron transporting characteristics. For years, ZnO has been studied widely to produce optical devices, lasers, piezoelectric sensors, photoconduction, light-wave conduction, and surface/bulk sound wave devices. Since the realization of ZnO-based practical devices depends greatly on the behavior of defects and the carrier transporting properties in ZnO thin films, it is a promising direction that would draw the researchers'attention in the future. In this paper, we did research focusing on the carrier distribution and basic electrical characteristics of a hexagonal microtube ZnO film, and the conclusions contained some reference values to further discussion of its optical and electrical characters.First, the high-frequency C-V profile of the sample was measured and certain energy variation was estimated to happen in ZnO conduction band. An effective model with a quantum well was also established, and the formulas were educed to calculate the capacitance numerically. Through simulation, our model seems reasonable, for the theoretical profile showing excellent agreement with the experimental one. Then, the apparent carrier concentration profile was extracted from the measured curve, which showed that the intrinsic defects in ZnO were evenly distributed, but the confinement happened in the well led to a region with high electron concentration.Second, based on the effective model, the distribution of two-dimension(2-D) electron gas was calculated theoretically by self-consistent solution of Poisson and Schrōdinger equations(SCPS). The equations were discretized by finite difference(FD) method and the source code for SCPS was achieved on Matlab software. Although the calculated distribution profile had obvious distortion when comparing with the one obtained from C-V profile, the accordance of total electron density in these two curves further proved that our model is practical and acceptable. In addition, the different influence of the effective quantum potential well parameters on the distribution of 2-D electron gas was also discussed.At last, the sample's I-V curve was measured and the major current component was decided to be the tunneling current raised by electrons in the ZnO/SiO2 interface. Thus, the charge distribution near the ZnO/SiO2 interface was calculated through SCPS method, so were the tunneling probability and the tunneling current density. The outcomes were compared with that obtained by classical F-N formulas and by measurement, demonstrating that, in small external electric field intensity, tunneling cunrrent was determined mainly by the trap states in the oxide, which consequently rose the distortion between theoreticl calculation and experiment.