Raman Spctrum Studies On La_0.5Sr_0.5CoO₃ Thin Films By Ion-Beam Sputtering

In this paper, the Raman spectra of perovskite-type La_0.5Sr_0.5CoO₃(LSCO) thinfilms was studied. The LSCO films which on yttria-stabilized zirconia(YSZ) andaluminates lanthanum (LaAlO₃)were obtained by ion-beam sputtering method. TheVibration frequencies of the micro-structure were explained heat-treating at differenttemperature and on different substrates. At the same time, an intensity relationbetween the Raman shifts and vibration of CoO₆ was found. The changed length ofCo-O bond length and computed the Raman vibration frequencies of LSCO wereanalyzed by quantum chemistry software Gaussian03, in order to predict the vibrationmodels of Co-O bond corresponding with Raman spectra. The energy of Co-Ochemistry bonds were also computed by Gaussian03.The studied results are follows:With the heat-treating temperature increasing, the relative strength of CoO₆octahedron vibration is weakened gradually, and the crystal structure of LSCO thinfilms is changed from random arrangement to orthorhombic. The length of Co-Ochemical bonds on different substrates is changed. For YSZ, the length of Co-Ochemical bonds and the size of crystal cell become longer. At same time, there is a red shift about the vibration frequency. But on the LaAlO₃, the length and vibrationfrequencies of Co-O chemical bonds don't change obviously.The computed results by Gaussian03 software are follows:On the LaAlO₃, the length of Co-O bonds were changed, from 1.895(?)(550℃)to 1.905(?)(750℃), corresponding with the crystal number changing from 3.79(?)(550℃)to 3.81(?)(750℃). But the Co-O chemical bonds on YSZ are not change. Thecrystal number is 4.01(?)(550-750℃). The energy of O-Al(Co-O-Al-O) bond islower than the energy of Co-O bonds on LaAlO₃. The energy of Co-O bond on YSZis lower than the energy of Co-O bonds on LaAlO₃. It is better that the LSCOcrystallized on LaAlO₃ than YSZ.