XPS Study of the Surface Layer of Ba0.6Sr0.4TiO3 Thin Films Deposited by Radio Frequency Magnetron Sputtering
射频磁控溅射 Ba0.6Sr0.4TiO3薄膜表层的XPS研究

Ba0.6Sr0.4TiO3 (BST) thin films were deposited on Pt/Ti/SiO2/Si substrate by radio frequency magnetron sputtering. The as-deposited films were crystallized by conventional thermal annealing (CTA) and rapid thermal annealing (RTA), respectively. The X-ray photoelectron spectroscopy (XPS) analysis show that the surface layer of the CTA-annealed film contains much non-perovskite BST phase, and has a thickness of 3~5nm approximately; while the RTA annealed surface layer contains much lower non-perovskite BST phase, and its thickness is less than 1nm. Meanwhile, with the annealing temperature increasing, the CTA-annealed surface layer increases, but for the film annealed by RTA, its thickness doesn't increase so obviously. The results also show that the formation of the non-perovskite BST phase could not be attributed to the surface adsorbate of CO or CO2, but to the elements such as oxygen. GXRD and AFM analysis manifest that the compact surface structure can effectively prevent the absorbed elements from diffusing into the BST film further, resulting in a thinner surface layer containing non-perovskite BST phase.