AFM and STM studies on In2O3 and ITO thin films deposited by atomic layer epitaxy

The surface morphology of In2O3 and In2O3:Sn (ITO) thin films deposited by atomic layer epitaxy has been studied by AFM and STM. The effects of film thickness, tin content and different doping schemes on the surface morphology were examined. Also the initial growth of SnO2 was studied in order to better understand the influence of the intermediate SnO2 pulses. Increasing film thickness led to increasing surface roughness, but the roughening rate decreased substantially after about 800 deposition cycles. In the ITO films the dependencies of roughness and electrical resistivity on the tin content were found to be parallel, both having a minimum at a tin content of about 4–7%. Deposition of a few cycles of SnO2 on a rough In2O3 film surface was found to decrease the surface roughness. In addition to the studies on the morphological development of the films, comparison between AFM and STM data allowed to obtain information on the electrical properties of the films.