The first-principles density functional theory is used to study the interaction of atomic hydrogen with ZnO surfaces. We find that atomic-hydrogen environments significantly reduce ZnO surface formation energies with hydrogen adsorption on the surface. The negative surface energy of the O-terminated ZnO(0001) surface is demonstrated in the O- and H-rich limits. The roughening and damage of ZnO surfaces are discussed in the context of the fluctuation of the surface formation energy.

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We conduct first-principles total-energy density functional calculations to study the interaction of H2 on ZnO surfaces. Four surface models of Zn-terminated (0001)-, O-terminated (0001)-, $(10{\bar 1}0)-$, and $(2{\bar 1}{\bar 1}0)-$oriented ZnO planes in the presence of H2 are evaluated. The relative stability of four different surface models is examined as a function of the chemical potentials of oxygen and hydrogen. We find that only surfaces of O-terminated (0001)-oriented ZnO models exhibit active sites for the dissociation of H2, which in turn enables the formation of water from dissociative chemisorption of 2H on the O-terminated ZnO(0001) surface. The surface energy of O-terminated ZnO(0001) surface in the presence of water was found to be negative under the O-rich and H-rich condition. The findings agree with the experimental observations that ZnO epitaxial layers are easily etched by hydrogen at typical growth temperatures.