Ternary WSe2(1-x)Te2x (x = 0-1) have been synthesized via chemical vapor transport (CVT) in a one-step synthesis, which exhibit two distinct structures. The atomic structure of the layered WSe2(1-x)Te2x alloys has been further studied by Z-contrast STEM. Since the image intensity in Z-contrast STEM imaging is directly related to the atomic number of the imaged species in thin flakes, we only examine the alloyed monolayers exfoliated from the bulk. Three regions (2H phase, the coexistence of 2H and 1Td phase, and 1Td phase) are identified in the complete composition of WSe2(1-x)Te2x (x = 0-1) alloy using EDXS and Raman spectroscopy. STEM images clearly confirm the semiconducting and metallic WSe2(1-x)Te2x alloys showing the hexagonal and orthorhombic lattices, respectively, and the random distribution nature of the Se and Te atoms arrangements in these alloys is also found. The PL spectra show that the optical band gaps of the WSe22(1-x)Te2xmonolayer can be tuned from 1.67 to 1.44 eV (2H semiconductor) and drop to 0 eV (1Td metal). Additionally, WSe2(1-x)Te2x atomic layer based FET devices confirm that 2H phase is p-type semiconductor but 1Td phase is metal. It is noted that the p-type bilayer 2H WSe2 and 2H WSe1.4Te0.6 FETs exhibit excellent electronic characteristic with effective hole carrier mobility up to 10 and 46 cm2V-1s-1 and on/off ratios up to 106, respectively.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering