Photoemission and x-ray absorption study of superconducting and semiconductingBa1−xKxBi

Abstract

Semiconducting Ba 0.9 K 0.1 BiO 3 and superconducting Ba 0.6 K 0.4 BiO 3 single crystals cleaved in situ have been studied by core level and valence band photoelectron spectroscopy and O K edge x-ray absorption spectroscopy. It was found that the general shape of the valence band spectrum agrees with the shape predicted by band structure calculations, but the intensity near the Fermi level was lower in the experimental spectrum as compared to the calculated. The O K edge spectra showed that the metallic phase is not related to the presence of doping inducted O 2 p holes. This property of Ba 1Ϫx K x BiO 3 shows that the semiconductor-metal transition of this system is of a different nature than that of the hole doped cuprate high-T c superconductors. The core level photoemission spectra of the cations showed a small asymmetry for Ba 0.9 K 0.1 BiO 3 . Corresponding spectra for Ba 0.6 K 0.4 BiO 3 showed a larger asymmetry resulting in a resolved high binding energy shoulder in the Bi 4 f spectrum. The origin of this feature is discussed.

Doping dependence of the electronic structure ofBa1−xKxBiOKobayashi1, Mizokawa2, Ino3 et al. 1999Phys. Rev. B162100View full textAdd to dashboardCite

“…Salem-sugui et al [17] observed a prepeak in the O 1s XAS spectra for BKBO with x = 0.0, 0.2 and 0.4 and a continuous change across the transition x ∼ x c was observed. Qvarford et al [18] also reported result for x = 0.1 and 0.4 and obtained similar results. A systematic study covering a wider concentration range, however, has been lacking.…”

“…7 (b), (c) and (d), we also show the results of the Bi 4f 7/2 , O 1s and Ba 3d core-level XPS spectra, respectively. According to the high resolution XPS study [18], the lineshapes of the core levels of the metallic BKBO are not single peaks but of multi-components with an energy-loss structure on the high binding energy (E B ) side. In fact, the core-level spectra in the metallic phase (particularly, x = 0.50 and 0.60) show somewhat broader peak widths than those in the insulating phase.…”

“…So far many studies have been performed on BKBO including transport, optical and tunneling experiments. Quite a few photoemission studies have also been reported [12][13][14][15][16] while there have been relatively few x-ray absorption spectroscopy (XAS) studies [17][18][19]. XAS gives us information about the unoccupied electronic states and, therefore, is suitable for studying the effect of hole doping on the electronic structure, as has been successfully applied to LSCO [20].…”

Core-level photoemission and x-ray absorption study of Na-covered and oxygen-deficientBa0.6K0.4BiONylén1, Beutler2, Zakharov3 et al. 1998Phys. Rev. BSelf Cite3110View full textAdd to dashboardCite

“…13 Before the photo-emission experiments, the oxygen-deficient samples were created by annealing superconducting single crystals (T c ϭ25 K) at 480°C for 1 h in an atmosphere at a pressure of 10 Ϫ2 torr. No superconductivity was observed after the annealing.…”

“…Previous attempts to address the Bi 4 f asymmetry have also been made by means of crystal defects, contaminations gathered at grain boundaries and chemical inhomogeneity of the samples. 13 Because of the reported variations in the Bi 4 f asymmetry from sample to sample with the same nominal composition, 13 it is important to consider the quality of the topmost layers of the single crystals when interpreting the Bi 4 f asymmetry.…”