Enhanced room-temperature spin-valley coupling in V-doped MoS2

Abstract

Achieving room-temperature valley polarization in two-dimensional (2D) atomic layers (2D materials) by substitutional doping opens new avenues of applications. Here, monolayer MoS 2 , when doped with vanadium at low (0.1 atomic %) concentrations, is shown to exhibit high spin-valley coupling, and hence a high degree of valley polarization at room-temperature. The atomic layers of MoS 2 (MS) and V-doped MoS 2 (VMS) are grown via the chemical vapor deposition-assisted method. The formation of new energy states near the valence band is confirmed from band gap calculations and also from the density functional theory-based band structure analyses. Time-reversal symmetry broken energy shift in the equivalent valleys is predicted in VMS, and the roomtemperature chirality-controlled photoluminescent (PL) excitation measurements indicate such a shift in valley exciton energies (∼35 meV). An enhanced valley polarization in VMS (∼42%) is observed in comparison to that in MS (<12%), while in MS, the chirality-controlled excitations did not show the difference in emission energies. Spin Hall effect of light-based optical rotation measurements indicate the asymmetric absorption among the two different chiralities of the incident light, hence supporting the existence of room-temperature valley polarization. This study opens possibilities of room-temperature opto-spintronics using stable 2D materials.

Ultrafast carrier dynamics in vanadium-doped MoS2 alloys

“…The intensity of the new modes increases with increasing concentration of V and hence these modes can be associated with the V doping of MoS 2 . 15,19 XPS measurements were performed to further confirm V doping. Fig.…”

“…In Fig. 1(c), the peaks corresponding to energies of 229.2, 232.3 and 235.4 eV represent the Mo energy states 3d 5/2 , 3d 3/2 and Mo 6+ , respectively, 15,19,29 and the energy peak at 226.4 eV is for the 2s state of S. 15,19,29 The peaks at energies of 162 and 163.2 eV correspond to the 2p 3/2 and 2p 1/2 states of S, respectively (Fig. 1(d)).…”

“…Monolayers of MoS 2 and V-doped MoS 2 were synthesized over a Si/SiO 2 substrate using a custom-built chemical vapor deposition (CVD) setup, as discussed in our previous reports. 15,19 In this method, MoO 3 (5 mg) and V 2 O 5 powders were used as precursors. An electronic grade Si/SiO 2 (300 nm) substrate was used for the growth.…”

Anisotropic Nonradiative Recombination of Carriers in a Few-Layered MoS2 Probed by Mid-IR Ultrafast Spectroscopy

“…Using the CVD Method. MoS 2 synthesis is carried out using a CVD-assisted method (2 zones), 46 having a quartz tube of length ∼120 cm and inner diameter ∼5 cm. In this method, MoO 3 (4 mg) is used as a precursor and kept in an alumina boat.…”

Piezoelectricity and valley polarization in a semilithiated 2H-TiTe2 monolayer with near room-temperature ferromagnetism

“…3,4 To utilize the valley index as an information carrier, it is an essential prerequisite to remove valley degeneracy via breaking time-reversal symmetry. Many techniques such as magnetic doping, 5,6 magnetic proximity, 7,8 and magnetic field 9,10 have been adopted to remove valley degeneracy and thus achieve valley polarization. Nevertheless, these external control avenues cannot cater to the requirements of modern electron devices for nonvolatility and miniaturization.…”