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Published on: December 5, 2015
Atomic Layer MoS2Te2(1- Ternary Alloys: Two-Dimensional van der Waals Growth, Band gap Engineering, and Electrical
DongHwan Kim1, Guen Hyung Oh2, Ansoon Kim1
1Materials and Convergence Metrology Institute, Korea Research Institute of Standards and Science, Daejeon 34113, South Korea.
Abstract:
Ternary alloys in two-dimensional (2D) transition-metal dichalcogenides allow band gap tuning and phase engineering and change the electrical transport type. A process of 2D van der Waals epitaxial growth of molybdenum sulfide telluride alloys (MoS2Te2(1-, 0 ≤ x ≤ 1) is presented for synthesizing few-atomic-layer films on SiO2 substrates using metal-organic chemical vapor deposition. Raman spectra, X-ray photoelectron spectra, photoluminescence (PL), and electrical transport properties of few-atomic-layer MoS2Te2(1- (0 ≤ x ≤ 1) films are systematically investigated. The strong PL peaks at 80 K from MoS2Te2(1- (0.45 ≤ x ≤ 0.93) reveal a composition-controllable optical band gap (Eg = 1.55-1.91 eV at 80 K). Electrical transport properties of MoS2Te2(1- alloys, where 0 ≤ x ≤ 0.8 and 0.93 ≤ x ≤ 1, exhibit p-type and n-type semiconducting behaviors, respectively. Remarkably, an increase in the Te composition of a few-atomic-layer MoS2Te2(1- (0 ≤ x ≤ 1) film left-shifts the threshold voltage of a MoS2Te2(1- (0 ≤ x ≤ 1) field-effect transistor. The narrower band gap energies of MoS2Te2(1- films with higher Te content cause a decrease in the on/off current ratios.
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