AES, XPS and SIMS characterization of YBa 2Cu 3O 7 superconducting high T c thin films

Abstract

High T c superconducting YBa 2Cu 3O 7− x (YBCO) films 100–200 nm thick have been grown in situ by ion beam sputter co-deposition using four Kaufman ion beam sources. As-deposited films have T c ( R = 0) at 74K. Postannealing improved T c ( R = 0) to 79 K. The critical current exceeded 5 × 10 4 A cm −2 at 77 K. Films were deposited on SrTiO 3, or on Si with an intermediate layer of SiO 2 or Y 2O 3. Auger Electron Spectroscopy (AES), X-Ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectroscopy (SIMS) were used to depth profile films deposited at 350 and 650°C. For quantification of XPS and AES analysis, standards of BaF 2, BaCo 3, BaO, BaO 2, CuO, Cu 2O, and Y 2O 3, and monocrystals of BaCuO 2 and YBa 2 O 3O 7 − x were measured. XPS binding energies and AES sensitivity factors were determined. Using the YBa 2Cu 3O 7 − x monocrystal new AES sensitivity factors differing from handbook factors have been established. Static SIMS data of the monocrystal was compared to thin film spectra of the first 1–2 monolayers showing almost identical cracking patterns.