Structure and vibrational spectra of ReSe₂ nanoplates

Abstract

Theoretical and experimental vibrational spectra of ReSe2 nanocrystals, synthesized by self‐limited chemical vapor deposition (CVD), are reported. Scanning electron microscopy reveals that the nanocrystals have the shape of polygon nanoplates (NPs), 20 nm thick and about 100–300 nm wide. X‐ray diffraction studies determined their triclinic structure (space group, P‐1 [no. 2]). The wavenumbers of the Raman‐ and infrared (IR)‐active phonon modes were calculated using the density functional perturbation theory (DFPT), along with the dispersion curves and phonon density of states. The set of theoretical phonon wavenumbers is found to correlate well with the experimental Raman and IR spectra. We established that, unlike ReS2, ReSe2 does not exhibit a “phonon gap.” Several “extra” bands in the experimental Raman spectrum of ReSe2 are argued to be defect‐induced contributions of phonons from F and Q critical points of the Brillouin zone. In addition, the effect of Fermi resonance is observed in the Raman spectrum of the ReSe2 NPs, which manifests itself in an increase of the intensity of second‐order bands due to their interaction with first‐order phonons.

Investigation of temperature‐dependent phonon dynamics of BixRe1−xSe2 (x = 0.0,0.1,0.5) via Raman spectroscopy

“…13 Furthermore, ReSe 2 has been suitable for field-effect transistor (FET) with high mobility of $96 cm 2 /VÁs. 14,15 Raman spectra is a thickness-dependent phenomena, and it can be seen that many Raman modes present in ReSe 2 nanoplates 16 are absent in the Raman spectra of Bulk ReSe 2 . However, there were no detailed discussion regarding the anharmonic process, first-order temperature coefficient and so on.…”

“…There are reports that comprise the vibrational properties of monolayer, few layer and bulk ReSe 2 . 16,18 A few reports have also highlighted the temperature dependency of the Raman peaks of Bi 2 Se 3 samples. 19,20 However, there could be contradictions in the peak assignment depending on the stress induced during the growth of the samples.…”

“…19,20 However, there could be contradictions in the peak assignment depending on the stress induced during the growth of the samples. 16 Considering all the previous reports, the present work analyses the temperature-dependent Raman spectra of ReSe 2 and the effect of Bi incorporation in the same, to estimate the effect of stress in the peak positions of the host. 21 The optical and thermal properties of a monolayer/few-layer ReSe 2 have already been reported.…”

Controllable growth of substrate-scale 2D ReSe2 thin films and their application for molecular detection via the SERS technique

“…[1][2][3] The covalent bond between Re and the neighboring atoms is very strong due to its extra electron. Such Re-Re bonding induces the formation of diamond shaped Re 4-clusters along the b [010] direction, resulting in in-plane anisotropic electronic and optical properties, [4][5][6] in particular anisotropic charge carrier mobility. 7 2D ReSe 2 has also weak interlayer coupling and exhibits thickness-independent direct band gap semiconductor behavior, in contrast to other TMDCs which show a transition from indirect to direct band gap when they change from bulk to monolayer.…”

Theoretical study of Raman scattering in MoS2xSe2(1 − x) layered alloys

“…By the types of Raman modes, the interactions in TMDs can be analyzed qualitatively and even quantitatively. [30][31][32][33] In the first publication, in the theory of alloyed crystals, Martin [34] proposed a simple model to describe the relative intensity of Raman scattering in alloyed crystals with the two-mode behavior. The local susceptibility, both linear and nonlinear, was assumed to be a sum of concentration-independent atomic contributions.…”