Anomalous dissolution of microindentation deformed zone of ITO/Si coated system

The joint effect of a film and a substrate on the modification of the mechanical properties of an ITO/Si coated system (CS), a promising material for solar cells, and its response to an external load in comparison with the Si substrate were considered. An unusual combination of a pronounced crack formation and a plastic character of indenter–sample contact zone was revealed. This feature was accounted for a high brittleness of the Si substrate and the enhanced plasticity of the ITO film that improves the mechanical characteristics of the whole ITO/Si structure, which is useful for its operation. Another unexpected result, the anomalous etching (dissolution) of the ITO film near the indentations, was found out when the ITO/Si CS was subjected to an aggressive medium. A preferable dissolution of the ITO film was detected in the deformed zone near the indentation (Df), commensurable with the dimension of the substrate elastic/plastic dislocation free zone which was two or three times larger than the indentation diagonal (d) and approximately ten times larger than the dislocation rosette around indentation on the Si support. An assumption was made that the effect is basically determined by high internal stresses in this zone and, hence, by weaker atomic bonds as compared with the undeformed part of the material. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)