X-ray photoelectron spectra of MgH₂

Abstract

Measurements of X-ray photoemission from magnesium hydride MgH, were made in an effort to further the fundamental understanding of the electronic structure of this metal hydride. The polycrystalline MgH, was compressed onto a metal holder to provide a smooth solid surface in a dry nitrogen box and then transferred into a ESCA system without exposure to air. Measurements were made immediately after the surface was scrapped in the vacuum. The binding energies of the photoelectrons from Mg 2s and 2p states were found to be 88.9 0.2eV and 50.1 0.2eV, respectively. The valence band spectrum shows an effective base width of approximately 8.8 eV, which is in reasonable agreement with the recent band structure calculation for MgH, , The photoelectron spectra also display features that can be identified as volume plasmon energy loss of 14.6 0.2eV. The data can be shown to be useful in calculating the average band gap energy (5.80eV) for MgH,.

Electron energy-loss spectroscopy study of MgH2 in the plasmon energy range

“…As a result, the free electron value has been used to determine, for example, the band gap energy. 21 However, with the present analysis of the perturbed (observed) plasmon energy in terms of multiple interband transitions, we may discard the assumption of a single interband transition (equal to the band gap energy) which has been applied so far to estimate the gap energy via the equation (E p 0 ) 2 ¼ E p 2 þ E g 2 . The study throws further light to the estimation of the band gap energy in tetragonal a-MgH 2 .…”

“…A number of studies, both theoretical and experimental, have been reported which are still not consistent and, therefore, leaving room for contradictory findings, including the value of the band gap energy. 4,5,[19][20][21][22][23][24][25][26] This discrepancy between experiment and the calculation is crucial barrier in tailoring the electronic structures aiming the applications mentioned above as well as is challenging in fundamental physics since the elements in MgH 2 , i.e., magnesium and hydrogen are well studied over a century.…”

Optical properties ofMgH2measuredin situby ellipsometry and spectrophotometry

“…Krasko 15 mentions a value of 5.16 eV for the band gap from unpublished work by Genossar. He and Pong 16 determined in an indirect way using Penn's formula 17 an average band gap of 5.8 eV. Yamamoto et al 18 report an optical transmission spectrum for a thin film in which the transmission vanishes at 6.05 eV (205 nm).…”

Exploring fundamental properties of Mg 0. 915 A 0 . 085 H 2 (A = Ti, Fe) for potential hydrogen storage application: First‐principles study

“…The Penn formula was used as in direct way by Krasko and Pong and they determined an average band gap of 5.16 eV, 5.8 eV, respectively, for MgH 2. 18,19 An observed shift of the band gap for some higher energy was illustrated, which was mainly due to formation of MgH 2. 20 Likewise for the material CaH 2 , which is one of the two most significant light metal hydrides (MgH 2 and CaH 2 ), an ionic bonding character was seen by considering the isolated electro-negativity of every Ca and H, which was affirmed by the X-ray photoelectron spectroscopy (XPS) study.…”