ETCHING EFFECT OF SUBSTRATE ON CRYSTALLINITY OF ORIENTED PLATINUM THIN-FILM

The treatment of MgO substrates by the H3PO4 wet-etching method were carried out in order to remove the impurities (H2O or CO2) in the surface layer of a MgO single crystal. Pt thin films were deposited on MgO substrates by rf-magnetron sputtering method. To evaluate the effect of the treatment, orientation and crystallinity of the obtained films were investigated. The etching rate in this experiment was about 2.90 nm/s. It was considered that crystallinity of the MgO substrates decreased due to H2O or CO2 in the surface region with a thickness of 1-mu-m. The surface roughness of substrates and thin films increased with increasing etching time for the MgO substrates. All of the obtained films showed [100]-orientation. The measurement of the rocking curve of (100) peak of the Pt film deposited on the MgO substrate etched for 5 min indicated that the half width was about 0.62 deg. and that the film had a good crystallinity. Pt films deposited on MgO substrates etched for 5 to 60 min exhibited epitaxial [100]-orientation from the measurement of half width for X-ray rocking curves, TEM micrographs, electron diffraction patterns and spacing of lattice planes in lattice images.