Characteristics of X-ray Absorption Near-edge Spectra Obtained from Various MgB2 Films

C. H. Hsieh ； C. N. Chang ； S. Y. Wang ； Pohan Lee ； H. C. Hsu ； Y. Cui ； X. X. Xi ； Eun-Mi Choi ； Sung-Ik Lee ； J. M. Chen

《Chinese Journal of Physics》 45卷2s2期 (2007/04) Pp. 163-174

並列摘要

X-ray absorption near-edge spectrum (XANES) of various MgB2 films prepared under different procedures has been measured by using synchrotron radiation. By comparing to the band structure calculation we observed that the major spectral peaks of B K edge XANES resulted from the empty states with p characters of boron in MgB2. The spectral peak near the threshold indicates the existence of the hole states in the valence band at the Fermi level. This is particularly clear in some c-axis oriented films. The peaks of B2O3 were common peaks in all of the films we studied, indicating the contamination of B2O3. This peak sometimes will smear the main spectral structure of MgB2 if it is seriously contaminated. The experimental XANES of Mg K edge results from the empty states with Mg p characters can be identified by comparing the experimental spectrum with the band structure calculations. A small core-hole effect resulted from the less electron screening of the Mg ions in MgB2 can be identified. There are empty states, as appear in the threshold spectral structure, extended from the Fermi level indicates the metal characters of Mg in MgB2. Little anisotropic characteristics between P(subscript x, y) and P(subscript z) can be identified from the polarization-dependent measurements, except the spectral intensity around 1314eV. Around that energy, the spectral intensity is higher for the electric field of the beam parallel than perpendicular to the boron planes, in accordance with the band structure calculations.