Vapor-phase growth and characterization of Mo_1−xW_xS₂(0 ≤ x ≤ 1) atomic layers on 2-inch sapphire substrates

Abstract

Atomically thin Mo(1-x)W(x)S2 (0 ≤ x ≤ 1) ternary compounds have been grown on 2-inch c-plane sapphire substrates with high uniformity by sulfurizing thin Mo(1-x)W(x) layers that were deposited at room temperature using a co-sputtering technique. Atomic force microscopy (AFM), Raman scattering, and optical absorbance spectroscopy (OAS) studies reveal that the Mo(1-x)W(x)S2 films consist of crystallites of two-to-four monolayers in thickness. X-ray photoelectron spectroscopy (XPS) shows that the core levels of Mo3d and W4f shift to lower binding energies while that of S2p shifts to higher ones with the increase in W compositions, which can be related to the larger electron affinity of W (0.8163 eV) than that of Mo (0.7473 eV). OAS has also shown that the direct bandgap of Mo(1-x)W(x)S2 is tuned from 1.85 to 1.99 eV by increasing x from 0 to 1. Both E(1/2)(g) and A(1g) phonon modes of the Mo(1-x)W(x)S2 films exhibit a two-mode behavior. The bandgap tuning and the two-mode phonon behaviors are typically the same as those recently observed in monolayer Mo(1-x)W(x)S2 obtained by mechanical exfoliation, thus shedding light on the bottom-up growth of large-scale two-dimensional Mo(1-x)W(x)S2 ternary alloys.

On the Stability and Electronic Structure of Transition-Metal Dichalcogenide Monolayer Alloys Mo1−xXxS2−ySey with X = W, Nb

“…At a mixture of 30% (W)-70% (Mo) and larger, the WS 2 -like modes start to appear, resulting in a two-mode behavior for each of the two normal modes. This is in a good agreement with experimental data reported by Liu et al [27]. …”

Nitrogen Ion Beam‐Mediated Dry Patterning of Conjugated Polymer Films for Organic Field‐Effect Transistors

“…When the nitrogen ion beam dose was low (1 × 10 13 ions cm −2 ), the S2p peaks were slightly shifted toward the higher energy direction owing to the influence of nitrogen ions (N + ) (note that the high energy shift in S2p peaks is often measured when sulfur atoms are bound or interacted with other moieties). [22,23] Further increased nitrogen ion dose (50 × 10 13 ions cm −2 ) significantly changed the S2p peaks to be a single peak by mixing of S2p(1/2) and S2p(3/2) peaks with considerably lower intensity. These results support that the P3HT chains were broken by the nitrogen ion beams with higher dose (intensity) and the broken moieties were wileyonlinelibrary.com unremained on the film parts.…”

Growth and synthesis of mono and few-layers transition metal dichalcogenides by vapour techniques: a review

“…Because sulfur evaporates very fast at high temperature, some authors report the use of two different crucibles, placed at different temperatures and distances from the substrate [102]: the nearest crucible starts to supply S by sublimation at lower temperatures, while the second one supplies S via evaporation before the entire consumption of the first source at higher temperatures occurs. For the growth of MoS 2 or WS 2 usually 0.5 -1 grams of S powders are placed in a crucible 7-15 cm away from the substrate, heated independently at temperatures ranging from 100 to 200 °C and delivered, in form of vapours, to the substrate.…”