Characterization of treated indium-tin-oxide surfaces used in electroluminescent devices

The influence of oxidative and reductive treatments of indium-tin-oxide (IT O) on the performance of electroluminescent devices is presented. The impro vement in device performance is correlated with the surface chemical compos ition and work function. The work function is shown to be largely determine d by the surface oxygen concentration. Oxygen-glow discharge or ultraviolet -ozone treatments increase the surface oxygen concentration and work functi on in a strongly correlated manner. High temperature, vacuum annealing redu ces both the surface oxygen and work function. With oxidation the occupied, density of states (DOS) at the Fermi level is also greatly reduced. This p rocess is reversible by vacuum annealing and it appears that the oxygen con centration, work function, and DOS can be cycled by repeated oxygen treatme nts and annealing. These observations are interpreted in terms of the well- known, bulk properties of ITO. (C) 1999 American Institute of Physics. [S00 21-8979(99)07815-9].