Surface Spectroscopy of High-Tc Y-Ba-Cu-O Superconductors

Various samples of Y-Ba-Cu-O system have been studied by Rutherford backscattering (RBS). At least within the selvage layer of 0.2 micron thickness, the real composition usually differs from its nominal composition, unless Y:Ba:Cu = 1:2:3. Surface infrared reflectance (SIR) under different temperatures from 4.2 K to 200K has been used for measuring energy gaps. Many electron spectroscopies are also measured under room temperature, but it is difficult to get reproducible and reliable results. Some preliminary results, however, are discussed.