Composition analysis of high-Tc superconducting thin films by quantitative x-ray fluorescence

A method is presented for determining the composition of thin films containing the elements Bi, Sr, Br, Cu, and Ca. Quantitative x-ray fluorescence (XRF) consisting of radioactive sources (secondary foil excitor 241Am-Mo source and 55Pe source), a Si(Li) detector, and a multichannel analyzer were employed. The XRF system was calibrated by using sol gel thin films of known element composition and also by sputtered thin films analyzed by the conventional Rutherford Back Scattering (RBS). The XRF system has been used to assist and optimize the sputter target composition required to produce high-Tc BiSrCaCuO films with the desired metal composition.

Pressure dependence of superconducting properties of MgB2 /

We prepared samples of MgB2 and ran sets of experiments aimed for investigation of superconducting properties under pressure. We found the value of pressure derivative of the transition temperature -1.2 ± 0.05 K/GPa. Then, using McMillan formula, we found that the main contribution to the change of the transition temperature under the pressure is due to the change in phonon frequencies. Griineisen parameter was calculated to be 7g = 2.4. Our results suggest that MgB2 is a conventional superconductor.