Fig. 6.

Formation of MoS₂/MoTe₂ lateral junction and WS_2−xTe_x alloy. a Schematic of 2H-MoS₂/2H-MoTe₂ in-plane heterojunction. b–e Optical micrograph (b); scale bar, 20 μm, confocal Raman mapping of E¹ _2g 2H-MoTe₂ (c), and 2H-MoS₂ (d) for MoTe₂/MoS₂ junction; scale bars, 50 μm and the corresponding diode I–V curve (e). A clear diode behavior with the band diagram of the MoTe₂/MoS₂ heterostructure reveals a type-II junction. For electrical measurements, source (MoTe₂) and drain (MoS₂) electrodes were fabricated by depositing 5/50 nm Cr/Au. f Optical micrograph of tellurized monolayer WS₂ flakes. WTe₂/WS_2−xTe_x junction; scale bar, 20 μm. g Raman spectra from each region of a and b in f. The Raman spectrum of 2H-WS₂ is also provided for comparison. h Circularly polarized PL spectra of 2H-WS₂ and the WS_2−xTe_x alloy (at 300 K) excited by σ+ polarized light at energy of 2.33 eV. The PL is red-shifted to ~ 0.1 eV and valley polarization is enhanced up to 37% in the WS_2−xTe_x alloy. Valley polarization (P _c) is defined as $P_{\mathrm{c}}=\frac{I\left(\sigma +\right)-I\left(\sigma -\right)}{I\left(\sigma +\right)+I\left(\sigma -\right)}$