Absorption-edge anisotropy inReS2andReSe2layered semiconductors

Abstract

Polarization-dependent absorption measurements of ReS 2 and ReSe 2 single crystals have been carried out in the temperature range between 25 and 500 K. A significant shift towards lower energies has been observed in the transmittance spectra of Eʈb polarization with respect to those corresponding to EЌb polarization. Analysis reveals that the absorption edges of ReS 2 and ReSe 2 are indirect allowed transitions. The parameters that describe the temperature dependence of the absorption edges with different polarizations in the van der Waals plane are evaluated. The results indicate that the electron-phonon coupling constants for Eʈb polarization are considerably larger than those of EЌb polarization. ͓S0163-1829͑98͒02748-9͔ PRB 58 16 133 ABSORPTION-EDGE ANISOTROPY IN ReS 2 AND . . .

Monolayer behaviour in bulk ReS2 due to electronic and vibrational decoupling

“…Upon transition from 1T (1H) to the distorted 1T structure, the energy gain is 1.1 (0.9) eV per ReS 2 molecule. In the distorted 1T structure, the Re atoms in the layer dimerize in such a way that they form a zigzag Re-Re chain extending along one of the lattice vectors 16,17 . Interestingly, by geometry consideration, the presence of the Re chains eliminates the energy benefit for the ReS 2 layers to order in Bernal (AB) or rhombohedral (ABC) stacking that occurs in other sTMDs.…”

Advent of 2D Rhenium Disulfide (ReS2): Fundamentals to Applications

“…Influenced by the covalent bonding, the lattice becomes a distorted 1T structure wherein Re atoms in the layer form a zig-zag Re-Re chain (Figure 4). [13,51,52] Because of the presence of Re chain inside each layer, energy difference of ReS2 layers when sliding from one layer to other becomes very nominal and therefore lacks order in stacking. In addition, one extra electron on the Re atoms results in significantly less intra-layer polarization and weakens the van der Walls interaction in interlayer.…”

“…In contrast ReS2 has reduced crystal symmetry which gives rise to anisotropic inplane optical properties. [21,51,[70][71][72] Research related to the electron-electron and hole-hole interactions in the excited state concluded that the anisotropic optical absorption on ReS2 was due to strongly bound excitons. The triclinic crystal structure of ReS2 leads to polarization dependent optical absorption.…”

Optical and Electrical Properties of Au- and Ag-Doped ReSe2

“…This is well consistent with the previous reports. [11][12][13] For the thin samples, a distinct absorption peak at around 1.3 eV is found. Compared with the PTR measurements that will be discussed later, this absorption peak is believed to originate from the E ex 1 excitonic transition.…”

“…Previous reports of absorption experiments only observed the indirect band gap. [11][12][13] In this work, the indirect band-edge transition is found to shift toward higher energy with decreasing the sample thickness, and for very thin samples several direct band-edge excitonic transitions are observed for the first time in the absorption spectra. On the other hand, electrical conductivity is measured and Hall measurement is performed, both at different temperatures ranging from 20 to 300 K. The activation energy is then derived from the Arrhenius plots of the conductivity and the Hall concentration.…”