Nanostructures produced by SPM voltage ramping in metal oxide films

In metal oxide film‐based nanosystems, the changes were produced and investigated by a scanning probe microscope (SPM). It is demonstrated that nanograins can be formed on the surfaces of ultrathin films (4 ÷ 10 nm) based on tin and indium oxides by the SPM electrical mode if the SPM tip is kept still on the surface and the bias voltage applied to the film is negative. In contrast to this, the positive bias voltage does not result in detectable changes of the film structures. The traceable transformations of the films are obtained only if the bias voltage exceeds a critical magnitude equal to about 2–3 V in SnO2 and about 5 V in In2O3. The nanograins are typically larger after a longer period of the electrical influence (typically 3 ÷ 5 min). The short‐term SPM analysis of the metal oxide surfaces during which a bias voltage is applied to the sample does not destroy the structure of the films in the tested points. The formation is faster and the nanogains are larger in the atmospheres with reduced amount of oxygen, e.g. in pure nitrogen, or with reducing gas, e.g. CO in air. The irreversible changes of the structure are shown being related to the hysteresis of voltamperic characteristics measured by the SPM before and during the initial stage of the grain formation. Based on this, the changes in the tin and indium oxides are explained by a redistribution of oxygen ions in the bulk of the films. Copyright © 2010 John Wiley & Sons, Ltd.