High-resolution secondary ion mass spectrometry depth profiling of superconducting thin films

Secondary ion mass spectrometry (SIMS) has been used to carry out in-depth analysis of a superconducting multilayer thin film. The film was a multilayer composed of YBa2Cu3O7-delta/10% cobalt-doped YBa2Cu3O7-delta/YBa2Cu3O7-delta (YBCO/Co-YBCO/YBCO) which had been laser-ablated on LaAlO3. Optimum conditions for SIMS depth profiling have been sought for the highest resolution of the position and width of the buried Co-YBCO layer. The margins of the Co-YBCO layer are characterised by the Co secondary ion decay length. This parameter has been measured for both oxygen and xenon primary ion beam sources and with respect to the angle of incidence of the primary ion beam on the sample. It has been found for both Xe+ and O-2(+) ion beam bombardment that the decay length of the leading edge of the Go-doped layer is invariant at 68 +/- 3 nm/decade for Xe+ and 53 +/- 3 nm/decade for O-2(+). The decay length of the trailing edge, however, gets progressively worse as the angle of incidence is increased above 30 degrees. This effect has been attributed, through the use of atomic force microscopy (AFM), to the development of topography in the crater base as the analysis proceeds. (C) 1998 Elsevier Science S.A.