Spectroscopic ellipsometry (SE) measurements were made on thin-film and single-crystal TiO2 anatase using a two-modulator generalized ellipsometer. The TiO2 films were epitaxially stabilized on a LaAlO3 substrate in the anatase crystal structure using reactive sputter deposition. The films were highly crystalline, possessing a “stepped surface” morphology indicative of atomic layer-by-layer growth. The SE results for the anatase film indicate that the material is essentially oriented with the c axis perpendicular to the substrate, but there is some anisotropy near the interface and the surface. Corrugations of the film surface, as observed using atomic force microscopy, are consistent with a surface structure needed to create cross polarization. Accurate values of the optical functions of crystalline anatase were obtained above and below the band edge using SE. Above the band edge, both the ordinary and extraordinary complex dielectric functions exhibited two critical points.

No abstract

The magnetic and phase properties of Co x Ti 1Ϫx O 2 anatase thin films grown epitaxially on ͑001͒ LaAlO 3 by a reactive rf magnetron cosputter deposition have been examined. Co x Ti 1Ϫx O 2 (x ϭ0.07) thin films exhibit room-temperature ferromagnetism, as evidenced by hysteresis in M-H loop. Chemical mapping indicates segregation of the Co dopant atoms in these films. However, x-ray photoelectron spectroscopy suggests that the segregated Co is not metallic, but in the Co ϩ2 state. These results are consistent with a segregated Ti-CoO phase being responsible for the ferromagnetic behavior.

No abstract

No abstract