Chromium oxides thin films prepared and coated in situ with gold by pulsed laser deposition

摘要

Chromium dioxide is a very suitable compound for spintronic devices. It is ferromagnetic at room temperature (T_c = 395 K) and has a half-metallic band structure. CrO_2 has been theoretically predicted to be100 percent spin polarized at the Fermi level. For some applications in spintronics low deposition temperatures are required. However, the fabrication of single phase thin films of CrO_2 at low temperature is quite difficult due to its metastable character. In this work we report our experiments to deposit thin films of chromium oxides by reactive pulsed laser deposition (RPLD). RPLD experiments were performed with a UV KrF excimer laser source (PIN_(FWHM) > = 20 ns, lambda = 248 nm) in different conditions regarding the target, the substrate temperature, the atmosphere inside the deposition chamber and the laser fluence. In order to prevent the reduction of CrO_2 to Cr_2O_3 in thin films preserved in ambient conditions some of the samples were capped with gold in situ using the same set-up. The composition and morphology of the deposited films were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. A higher and stable content of CrO_2 in the deposited films was evidenced in the case of samples capped with Au. Subsequent analysis performed after 4 months showed no difference in the content of the film.