Low Energy Ion Scattering Studies of Sodium Segregation in ZnO

The segregation of Na and K, native sub ppm bulk impurities in ZnO is studied on its polar surfaces using photoemission and low energy ion scattering techniques. On the (000\(\overline 1 \))-face, the resulting lowering of the electrostatic surface energy acts as a strong additional segregation force. The angular dependence of the ion intensities, backscattered from the segregated Na, shows that the Na atoms are slightly protruding out of the (000\(\overline 1 \)) surface.