Photoluminescence emission and Raman response of monolayer MoS_2, MoSe_2, and WSe_2

Abstract

We mechanically exfoliate mono- and few-layers of the transition metal dichalcogenides molybdenum disulfide, molybdenum diselenide, and tungsten diselenide. The exact number of layers is unambiguously determined by atomic force microscopy and high-resolution Raman spectroscopy. Strong photoluminescence emission is caused by the transition from an indirect band gap semiconductor of bulk material to a direct band gap semiconductor in atomically thin form.

Influence of the substrate material on the optical properties of tungsten diselenide monolayers

“…Reflection contrast [34][35][36], transient absorption [35], time-integrated photoluminescence (PL) [37,38] and time-resolved photoluminescence (TRPL) [39,40] experiments, have been performed to study the emission properties of WSe 2 . In prior studInfluence of the substrate material on the optical properties of tungsten diselenide monolayers 2 S Lippert et al ies on WSe 2 , layers were deposited on SiO 2 /Si substrates [41,42], sapphire [43,44], graphene [45], and fused silica (quartz) [34,46] or sandwiched between layers of hBN [47].…”

Vibrational spectrum renormalization by enforced coupling across the van der Waals gap betweenMoS2andWS2Fan1, Zhu2, Ke3 et al. 2015Phys. Rev. B311221View full textAdd to dashboardCite

“…The former is due to enhancement in restoration force by interactions between the S atoms from neighboring layers; the latter is attributed to enhanced dielectric screening of long-range Coulomb interaction between the metal atoms (Mo or W), because different from the vibration involving only S atoms in the A 1 ' mode, in the E' mode the metal atoms also vibrate. 17,18 Typical Raman spectra of MoS 2 monolayer, WS 2 monolayer, and WS 2 /MoS 2 hetero-bilayers at ambient pressure (P ≈ 0) are shown in Fig. 1(b).…”

“…This is consistent with earlier reports that show negligible interaction between neighboring layers in as-stamped bilayers. [15][16][17][18] Upon the application of high pressure, all four Raman peaks start to shift toward higher wavenumbers, accompanied with peak height reduction and width broadening. Some of the Raman spectra are selectively shown in Fig.…”

Real-time monitoring of 2D semiconductor film growth with optical spectroscopy

“…The corresponding full width of half maximum (FWHMs) of the A g 1 peaks are 5.19 and 4.65cm −1 for the MoSe 2 films with thicknesses of 0.41 nm and 1.27 nm, respectively. Comparing with the FWHM of the A g 1 peak measured from the mechanically exfoliated 2D MoSe 2 layer, which is around 1cm −1 [30], these numbers are relative larger. This observation suggests the formation of defect rich 2D MoSe 2 layers with relative small grain size [20].…”