Optical and mechanical consequences of microstructural alteration of alpha platinum dioxide films

The microstructure of sputtered alpha platinum dioxide consists of a porous random assembly of platelets. A sweeping motion with very light pressure, by either a sharp or blunt object, leaves a track clearly visible, in reflected light, that stands in contrast to the opaque brown background of the intact film. Microstructural analysis utilizing atomic force microscopy revealed a flattening of the platelets in the affected areas. High reflectivity of the flattened portion is apparently a consequence of the relatively high refractive index of this material. X-ray diffraction by the flattened platelets shows a significant enhancement of the intensity of the 001 reflection corresponding to the alignment of the crystals parallel to the substrate. The work required to flatten the platelets along a microscopic track was deduced from sensitive friction force measurements. Electrical resistivity of the flattened film is moderately lower than that of the intact film. The phenomenon described here might be of importance for data storage or for alignment in lithographic reproduction of multilevel electronic circuits.