Photoelectron spectroscopy study of ammonia adsorption on ZnO(10(1)over-bar0)

Ammonia adsorption on the nonpolar ZnO(10(1) over bar 0) surface has been studied using X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Ammonia adsorbs on the surface molecularly at room temperature. Adsorption induces the shift of the O 2p dangling bond state to the higher binding energy side. This implies the formation of the hydrogen bond between the surface O atoms and the H atoms of NH3. Annealing the ammonia-covered surface induces the partially decomposed NHx (x = 1, 2) species. All adsorbates are removed at the surface temperature of 625-650 K. When the surface is precovered with K, no adsorbed ammonia is observed. Not only a site blocking effect but also a nonlocal effect for poisoning is proposed.