An X-ray photoemission study of the effect of gamma-irradiation on fluorinated (Tl0.5Pb0.5)Sr1.6Ba0.4Ca2Cu3Oy high-T-C superconductor

X-ray photoemission spectroscopy (XPS) has been used to investigate the eff ect of gamma -irradiation on F1s, Cu2p(3/2) and Sr3p(3/2) binding energies of fluorinated (Tl0.5Pb0.5)Sr1.6Ba0.4Ca2Cu3Oy superconductor. The F1s peak of this material started to disappear as gamma -dose was increased, indicat ing that gamma -irradiation creates vacancies in F and hence O sites las F partially replaces O). The Cu2p(3/2) satellite, that is typical of Cu2+, di sappears and a low energy shoulder, that is a signature of Cu1+, develops a s gamma -dose increases. Also the binding energy of Cu2p(3/2) was decreased with increasing gamma -irradiation, indicating a decrease in the average C u valency. On the other hand, the binding energy of Sr3p(3/2) increases wit h increasing gamma -dose up to 30 Mrad. This also indicates a decrease in t he hole concentration in the Cu-O planes of the fluorinated Tl-1223 because of removal of F/O from the Cu-O planes. As the irradiation dose is increas ed to 50 Mrad, the binding energy of Sr3p(3/2) decreases. This may be due t o additional F/O removal from the Sr/Ba-O planes. (C) 2001 Elsevier Science B.V. reserved. All rights reserved.