Experimental and theoretical study of the electronic structure of HgO andTl2O3

Abstract

The electronic structures of HgO and Tl 2 O 3 have been investigated by valence and core-level x-ray photoemission, x-ray absorption, and x-ray emission spectroscopies. Valence-band photoemission under Al K␣ excitation is dominated by the metal 5d partial density of states and thus provides a sensitive probe of shallow core mixing into the O 2p valence-band states. Conversely O K shell emission is determined by the O 2p partial density of states and therefore allows the extent of corresponding mixing of O 2p character into the shallow core states to be measured. The experimental work is supported by band-structure calculations carried out within the framework of density-functional theory. It is shown that the bonding in HgO involves significant mixing between O 2p states and both Hg 6s and shallow core 5d states: the calculated O 2p partial density of states mirrors the O K shell emission spectrum and reveals significant O 2p character within the shallow core Hg 5d states. There is, however, little direct on-site mixing between the Hg 6s and 5d states. In Tl 2 O 3 , the hybridization of the deeper metal 5d states with O 2p states is much less pronounced than in HgO. Moreover, the states at the bottom of what is conventionally regarded as the O 2p valence band are found in fact to have very strong Tl 6s atomic character. The photoemission spectrum of Tl 2 O 3 shows a well-defined metallic Fermi edge: the shape of the structure around the photoemission onset suggests that the metallic nature of Tl 2 O 3 arises from an occupation of states above the main valence-band edge, probably arising from oxygen vacancy defects. The conduction electrons of Tl 2 O 3 are strongly perturbed by ionization of Tl core levels, giving rise to distinctive plasmon satellites in core x-ray photoemission spectroscopy.

The electronic structure of the antimony chalcogenide series: Prospects for optoelectronic applications

“…Sb 2 Te 3 thus takes on a symmetric structure and the Sb 5p do not mix with the states at the top of the VB. The results of the Sb chalcogenide series are in support of previous studies of the revised lone pair model [58,59,60,62,63,64,113]. A similar reduction in lone pair activity from O to Te was observed previously for the Sn monochalcogenide series and from PbO to PbS [62].…”

“…The change from a highly distorted Sb 2 O 3 structure to the hexagonal symmetric Sb 2 Te 3 structure can be explained by the formation of asymmetric density or lone pairs, on the Sb III cations. The lone pair formation is a result of the stabilisation of the Sb 5s-anion p anti-bonding states by the Sb 5p states at the top of the VB, similar to other lone pair materials [58,59,60,62,64,113]. The asymmetric density on the Sb III cations weakens down the series due to the increase in energy gap between the Sb 5s and Ch p states, as also observed for the Sn monochalcogenide series [63].…”

Photoemission analysis of chemically modified TlBr surfaces for improved radiation detectors

“…10 Figure 2 presents the Tl 4f 7/2,5/2 core-level spectra for the chemically modified series. From the literature, the Tl 4f 7 [11][12][13][14][15] In addition, the spin-orbit splitting for the Tl 4f peaks is 4.4 eV. Comparing these literature values with the Tl 4f 7/2,5/2 binding energies summarized in Table II, we conclude that the surfaces have oxidized and that the SOCl 2 , HCl and Br:MeOH treatments initially reduce the Tl surface oxide resulting in the small lower binding energy feature indicative of Tl metal.…”

High-pressure structural and elastic properties of Tl2O3

“…11 Consequently, many properties of Tl 2 O 3 are unknown. In particular, it was long thought that this compound behaves as a metallic conductor; [12][13][14] however, it has been recently shown that it is a degenerate n-type semiconductor. 15 This result is in good agreement with transport measurements which suggest that n-type conductivity comes from oxygen deficiency in the crystalline lattice.…”