LASER IRRADIATION EFFECTS IN YBA2CU3O7-DELTA THIN-FILMS ON METALLIC AND SINGLE-CRYSTAL SUBSTRATES, A MICRO-RAMAN STUDY

In-depth micro-Raman study of YBa2Cu3O7-delta a thin films deposited o n metallic substrates (hastelloy-C, inconel-600 and stainless steel-30 4) with a TiN buffer layer (YBCO-M) and single crystal LaAlO3 (YBCO-L) substrate has been carried out in order to investigate the relative p henomenological differences between the behavior of these films on dif ferent substrates, A comparative study of films on these substrates re vealed that the bandwidths of the prominent oxygen vibrations in YBCO- M are significantly larger than those in the case of YBCO-L and a defe ct induced, strong and broad feature around 570 cm(-1) is always prese nt in the Raman spectra of YBCO-M, The broadening of bands and the pre sence of the 570 cm(-1) band have been attributed to the disorder indu ced by buffer layer in YBCO-M, Variation of the incident laser power ( P-L) from 1 to 10 mW, or a continuous irradiation were found to induce unusual, irreversible but, dissimilar changes in the Raman spectra of YBCO-M and YBCO-L, A significant change in the intensity distribution of oxygen vibrations and a decrease in the bandwidth of the out-of-ph ase mode in YBCO-M films have been attributed to an improvement in the crystallinity of YBCO-M films due to oxygen ordering in the CuO2 plan es, Whereas, in YBCO-L, the laser irradiation causes oxygen removal fr om the CuO chains and formation of impurity phase BaCu2(O). Distinct l aser induced changes in the Raman spectra of YBCO-M and YBCO-L have be en explained in terms of photoinduced ordering and local heating effec ts respectively.