Controlled underdoping of cuprates using ultraviolet radiation

A method for a controlled change of the doping level of high-temperature su perconductors with ultraviolet radiation is presented. With photoemission i t is shown that the exposure of Bi2Sr2CaCu2O8+delta samples to the light of a He gas-discharge lamp causes oxygen desorption. From measurements of the Fermi surface, it is found that the oxygen desorption causes a decrease of the doping level of the superconductors. From the desorption cross section s that strongly depend on the photon energy, two different oxygen desorptio n channels are inferred. This procedure for decreasing the doping level has the advantage that the crystallinity of the sample is not altered and that the doping level can be simultaneously measured by photoelectron spectrosc opy. (C) 1999 American Institute of Physics.