COMPOSITIONAL DEPENDENCE OF THIN-FILMS OF BIPBSRCACUO ON TARGET TO SUBSTRATE DISTANCE

Using magnetron sputtering techniques, several thin films of supercond ucting BiPbSrCaCuO were fabricated by varying the distance between the substrate (single crystal of MgO with polished (100) plane) and the t argets. During the deposition the gas pressure was kept constant at 0. 3 mbar (1 mbar = 0.1 kPa) and the substrate temperature was kept at 70 0 degrees C. An energy-dispersive X-ray fluorescence was designed usin g a radioisotope source with a secondary target and a Si(Li) X-ray spe ctrometer and it was used to measure the atomic composition of the fil m quantitatively. It was found that the Ca concentration relative to S r increases linearly as the distance between the substrate and the tar gets increases. However, both Cu and Bi show a more complex variation of concentration with distance. The X-ray diffraction results also ind icated that the films are grown epitaxially along the C axis, which sh owed a semiconducting behaviour with T-C,T-zero below 60 K.