ZnO(101¯0) is unstable in moderate pressures of water

Abstract A ZnO ( 10 1 ¯ 0 ) single crystal was investigated using in situ scanning tunneling microscopy and X-ray photoelectron spectroscopy. In roughly 1 mbar water the surface roughens within minutes. Hereby, the formation of ( 0001 ) - or ( 000 1 ¯ ) -type steps is favored over the formation of ( 1 2 ¯ 10 ) -type steps. The roughened surface is stable in ultra-high vacuum and does not exhibit a different amount of hydroxylation or adsorbed water compared to the as-prepared surface. The speed of the roughening is related to the total volume of water supplied to the surface rather than the water pressure.