Self-diffusion, electrical properties and defect structure of undoped, single-crystal zinc oxide.

摘要

Oxygen and zinc tracer self-diffusion coefficients were measured using Secondary Ion Mass Spectrometry (SIMS). For oxygen diffusion, {dollar}sp{lcub}18{rcub}{dollar}O{dollar}sb2{dollar} was used as the tracer, and diffusion was measured from 850-1200{dollar}spcirc{dollar}C as a function of crystallographic orientation at {dollar}rm psb{lcub}Osb2{rcub}{dollar} = 1.0 atm. Diffusivities measured in this manner were isotropic, and the activation energy was 3.6-4.1 eV, indicative of an oxygen vacancy mechanism.; Zinc diffusion was measured using {dollar}sp{lcub}70{rcub}{dollar}Zn as the tracer as a function of {dollar}rm psb{lcub}Osb2{rcub}{dollar}, orientation, and temperature from 850-1020{dollar}spcirc{dollar}C. Diffusivities measured were isotropic with an activation energy of 3.9 eV, suggesting that zinc diffusion occurs via a vacancy mechanism.; The evaporation of ZnO was considered in its effect on the measurement of diffusion. For oxygen diffusion, evaporation was controlled by placing samples inside ZnO crucibles. For zinc diffusion, evaporation was controlled by placing sintered ZnO pellets adjacent to the samples during diffusion anneals. The effects of evaporation are discussed.; Electrical conductivity and thermopower were measured in the c-direction as a function of temperature and {dollar}rm psb{lcub}Osb2{rcub}{dollar}. Measurements are consistent with n-type conductivity. The behavior of the electrical properties as a function of oxygen pressure indicate the presence of an extrinsic donor impurity at intermediate-{dollar}rm psb{lcub}Osb2{rcub}{dollar}, and an intrinsic defect equilibrium at low-{dollar}rm psb{lcub}Osb2{rcub}{dollar}.; A defect chemistry analysis of the diffusion and electrical data suggests that impurities dominate the conductivity at intermediate oxygen pressure while the intrinsic equilibrium between electrons and oxygen vacancies dominates at reduced {dollar}rm psb{lcub}Osb2{rcub}{dollar}.