Optical property of PtOx at elevated temperatures investigated by ellipsometry

The optical properties of PtOx thin films used for the optical recording layer of super resolution near-field structures (super-RENS) are studied at high temperatures. A series of PtOx thin films for various molar oxygen fraction x were prepared using the reactive magnetron sputtering technique. From the ellipsometric studies, it is found that the complex refractive index of PtOx changes monotonically from that of metallic Pt to that of dielectric PtO2 as the molar oxygen fraction increases. When temperature increases from 30 to 700 degrees C, all PtOx is completely decomposed at 549 degrees C and, for the samples with x larger than 1.3, the condensation of porous Pt films is completed at 700 degrees C. The surface roughness of PtOx thin films with x larger than 1.3 increases markedly after temperature ramping and PtOx thin films evolve into Pt metal by passing through three steps of oxidization, decomposition and condensation.