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Issue 1, 2014
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Vapor-phase growth and characterization of Mo1−xWxS2 (0 ≤ x ≤ 1) atomic layers on 2-inch sapphire substrates

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Abstract

Atomically thin Mo1−xWxS2 (0 ≤ x ≤ 1) ternary compounds have been grown on 2-inch c-plane sapphire substrates with high uniformity by sulfurizing thin Mo1−xWx 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 Mo1−xWxS2 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 Mo1−xWxS2 is tuned from 1.85 to 1.99 eV by increasing x from 0 to 1. Both E12g and A1g phonon modes of the Mo1−xWxS2 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 Mo1−xWxS2 obtained by mechanical exfoliation, thus shedding light on the bottom-up growth of large-scale two-dimensional Mo1−xWxS2 ternary alloys.

Graphical abstract: Vapor-phase growth and characterization of Mo1−xWxS2 (0 ≤ x ≤ 1) atomic layers on 2-inch sapphire substrates

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Article information


Submitted
24 Aug 2013
Accepted
16 Oct 2013
First published
17 Oct 2013

Nanoscale, 2014,6, 624-629
Article type
Paper

Vapor-phase growth and characterization of Mo1−xWxS2 (0 ≤ x ≤ 1) atomic layers on 2-inch sapphire substrates

H. Liu, K. K. A. Antwi, S. Chua and D. Chi, Nanoscale, 2014, 6, 624
DOI: 10.1039/C3NR04515C

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