Electronic Bandgap and Exciton Binding Energy of Layered Semiconductor TiS₃

Abstract

A study of the electronic and optical bandgap is presented in layered TiS3, an almost unexplored semiconductor that has attracted recent attention because of its large carrier mobility and inplane anisotropic properties, to determine its exciton binding energy. Scanning tunneling spectroscopy and photoelectrochemical measurements are combined with random phase approximation and Bethe–Salpeter equation calculations to obtain the electronic and optical bandgaps and thus the exciton binding energy. Experimental values are found for the electronic bandgap, optical bandgap, and exciton binding energy of 1.2 eV, 1.07 eV, and 130 meV, respectively, and 1.15 eV, 1.05 eV, and 100 meV for the corresponding theoretical results. The exciton binding energy is orders of magnitude larger than that of common semiconductors and comparable to bulk transition metal dichalcogenides, making TiS3 ribbons a highly interesting material for optoelectronic applications and for studying excitonic phenomena even at room temperature.

Ab initio and semiempirical modeling of excitons and trions in monolayer TiS3

“…According to our DFT calculations, the TiS 3 monolayer has a direct band gap of 0.30 eV at the point in the BZ, similar to the earlier PBE calculations [40,41]. As expected, the DFT gap is much smaller than the experimental electronic band gap and the optical band gap of TiS 3 , which are reported to be around 1.2 and 1.1 eV, respectively [23][24][25]. Earlier calculations with the HSE06 hybrid functional reported the electronic band gap of monolayer TiS 3 as 1.05 eV [40], and GW calculations using the plasmon-pole approximation yielded around 1.15 eV [42,43].…”

“…The absorption spectra of pristine TiS 3 monolayer are remarkably different for different polarization directions due to the crystal anisotropy. Earlier theoretical works also predicted the polarization dependent absorption spectra of bulk TiS 3 , but did not investigate the band composition responsible for the peaks in their absorption spectra [24,43]. In Fig.…”

“…For instance, in contrast to the layered TMDCs, TiS 3 exhibits a direct band gap in both monolayer and bulk form of about 1 eV. It is important to note that the band gap and its direct character depend very slightly on the thickness and the stacking order of the constituent layers [23][24][25][26]; it changes slightly on the other hand with the application of tensile stress to the material [27]. It has also been shown that TiS 3 transistors show very high electron mobility and the current-voltage characteristics exhibit strong nonlinearity [28,29].…”

Electronics and optoelectronics of quasi-1D layered transition metal trichalcogenides

“…Working in this line, Molina-Mendoza et al have studied the electronic bandgap of TiS3 by means of scanning tunnelling spectroscopy (STS) on TiS3 at room temperature and determined the exciton binding energy by comparing the electronic bandgap with the optical bandgap. 47 STS measurements were carried out on mechanically exfoliated TiS3 transferred onto a Au(111) substrate. Tunneling current-bias voltages curves are used to determine the valence and conduction band values with respect to the Fermi level (Figure 10(a)).…”

Temperature-Dependent Raman Spectroscopy of Titanium Trisulfide (TiS3) Nanoribbons and Nanosheets

“…31,32 Unlike Mo-and W-based dichalcogenides (which present a direct bandgap only at the single-layer limit) TiS3 has a direct bandgap of ~1.0 eV which is optimum for photovoltaic and photocatalysis applications. [33][34][35] Moreover, recent theoretical works predict that the ideal carrier mobility of TiS3 can reach values as high as 10000 cm 2 V -1 s -1 . 36 A study of the vibrational properties of trichalcogenides is important to understand their electron-phonon interaction, which plays an important role in the electronic performance of nanodevices and it can even be the main mechanism limiting the charge carrier mobility.…”