Photoemission study of chain- and layer-type TlS crystals

Abstract

Thallium monosulphide is a mixed-valence compound containing monovalent and trivalent Tl ions. The compound crystallizes in two different structures, the tetragonal TlSe type and the monoclinic type. Photoemission studies were carried out, using a synchrotron photon source, on TlS crystals with both the TlSe- and -type structures. Comparison of the spectra shows that the line shape of the Tl 5d core level is more asymmetric in the TlSe type than the type. The asymmetry reflects the density of states near the Fermi level of the crystals. It was also found that as the incident photon energy increases the intensities of the valence band peaks increase relative to those of the Tl 5d core levels. Comparing the intensity ratios with the calculated photoionization cross section ratios, the characters of the valence bands were discussed.

Characteristics of photoconductivity in Tl2S layered single crystals

“…2) and the crystals under study have a high photosensitivity (see Figs. 4,5), which could be confirmed by the values of the carrier lifetime (CLT) in all the ranges under study of temperature, applied voltage, and light intensity (see Figs. 7,9,11).…”

“…Photoemission studies, using a synchrotron photon source, on TIS crystals have been reported by Kashida et al [5]. In these studies, the photoelectron energy distribution curves with different incident photon energies showed that the binding energies of the Tl 5d 5/2 and Tl 5d 3/2 core levels for Tl 2 S crystal are 15.55 eV and 13.36 eV, respectively.…”

“…single crystals have been estimated by Kashida et al [5]. The optical absorption studies of Tl 2 S have been investigated by Estrella et al [11] and suggest that there are direct forbidden transitions with a band gap of 1.12 eV.…”

Characteristics of Optical and Photoconductive Properties in Bulk and Thin Film of TlS2Single Crystals

“…A new description and a new discussion of the stereochemistry have been investigated by Giester et al [7], in which they reported that the interatomic distances will always be given to two decimals (σ < 0.01Å), although for the Tl-Tl distances three decimals would be adequate (σ < 0.005Å). Photoemission studies, using a synchrotron photon source, on TlS crystals have been reported by Kashida et al [3]. They reported that the binding energies of the Tl 5d 5/2 and Tl 5d 3/2 core levels for Tl 2 S crystal are 15.55 and 13.36 eV, respectively.…”

“…TlS single crystal is known as a good photoconductor, its electronic structure is not well known [3]. Synthetic Tl 2 S is known to be a black, soft, and extremely laminar substance.…”