INFLUENCE OF 30 MEV S-32 IRRADIATION ON THE ELECTRONIC STATES OF LN2-XCEXCUO4-DELTA CUPRATES

Polycrystalline samples of Ln2-xCexCuO4-delta (Ln = Nd, Sm) (the T' ty pe high-T(c) superconductors) with x = 0 and 0.15 as a ''simple'' mode l compound for other HTSC's have been irradiated with 30 MeV S-32 ions at room temperature in order to study the differences in electronic s tructure between ideal and disordered materials. Irradiation has been performed in an ultra-high vacuum chamber with subsequent in-situ phot oelectron spectroscopy (PES). S-32 fluences have been varied between 2 x 10(12) cm-2 and 1 x 10(15) cm-2. After irradiation the valence band and several core-level spectra of Cu, 0 and Ln = Nd, Sm have been rec orded. For each compound and fluence we observe preferential depletion of oxygen and deposition of these fragments on the surface, indicated by characteristic changes in the valence band and O 1s core-level spe ctra. For low fluences (phit < 10(-13) CM-2) oxygen removement takes p lace preferentially in the Ln-O planes (i.e. in the dopant layers). At a certain threshold fluence (phit)Cu+, which depends essentially on t he Ln-O hybridization, we observe strong formation of monovalent coppe r in the valence band and Cu 2p spectra indicating considerable oxygen depletion also of the Cu-O layers.