First-principles Study Of Doping And Diffusion Property In ZnO

In this thesis, we have investigated doping and di?usion property in ZnO, by first-principles calculations. We systematically study the doping behavior in the kineticspoint view, via calculating the relevant di?usion energy barrier.First, we check the so-called LDA (GGA)+U corrected method in detail. Bycalculating the transition energy levels of Zn vacancy and O vacancy, we find thattransition energy levels are linearly dependent on U parameter. Then, we calculate thetransition energy levels of extensive n-type and p-type point defects, and find that therelative position of the transition energy levels vary slightly after correction, notice thattransition energy level of NO is too large (0.9 eV), which indicate that such correctedmethods have some problems for quantitative calculation.We investigate the di?usion property of intrinsic point defects in ZnO by CI-NEBmethod, and find that, Zn interstitial can di?use e?cient by both interstitial mecha-nisms and kick-out mechanisms, with 0.3-0.5 eV energy barrier; Zn vacancy and Osplit interstitial di?use with about 1 eV energy barrier. O split interstitial di?uses with0.5 eV energy barrier. The di?usion of O vacancy is sensitively dependent on thecharge states, 1.5 eV for +2 charge state, 2.5 eV for 0 charge state. The di?usion isessentially isotropic. Based on the calculation results, we can understand why ZnO isvery resistive to high-energy radiation.Then we investigate the vacancy mechanism of B, Al, Ga and In in ZnO, andobtain the relevant di?usion energy barrier, which is useful for understanding the ex-perimental di?usion data.Using CI-NEB method, we investigate the stability and di?usion behaviors of Li,Na, K and Ag interstitial, and find Li, Na and Ag interstitial is very stable, with morethan 1.6 eV annihilation energy barrier. K interstitial is less stable, with about 0.8 eVannihilation energy barrier. Li, Na, K and Ag interstitial are all fast di?users, therein,the di?usion of Li is isotropic, and di?usion of Na, K and Ag is highly anisotropic. We also investigate the stability and di?usion behaviors of N, P, As and Sb interstitial, andfind that N, P, As interstitial is stable, therein N is not easy to di?use with 1.8 eV energybarrier, P and As interstitial is easy to di?use. Sb tends to occupy the configurationwhich Zn is pushed o?-site.At last, we have developed a new calculation scheme to investigate the defect levelof point defects, that is, putting two defects in one supercell and observing the chargetransfer between them.