Diffusion and thermal stability of hydrogen in ZnO

We perform both first-principles calculations and kinetic Monte Carlo (kMC) simulations to study the diffusion and thermal stability of hydrogen in ZnO. The migration energy of a substitutional hydrogen (H-O) is 1.7 eV, much higher than the value of 0.4-0.5 eV for an interstitial hydrogen (H-i). Using as input the calculated energy barriers for H diffusion, kMC simulations show that while H-i diffuses out at low temperature, the thermal stability of H-O is maintained up to 475 degrees C, in good agreement with the annealing data. In addition, our calculations suggest that injected hydrogen from air turns into H-O, causing n-type conductivity. (C) 2008 American Institute of Physics.