1. Substrate induced tuning of compressive strain and phonon modes in large area MoS 2 and WS 2 van der Waals epitaxial thin films
- Author
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Rajib Sahu, Ranjan Datta, B. Vishal, Dhanya Radhakrishnan, Anomitra Sil, Chandrabhas Narayana, and D. S. Negi
- Subjects
Condensed Matter - Materials Science ,Materials science ,Condensed matter physics ,Phonon ,Band gap ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Nanotechnology ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Pulsed laser deposition ,Inorganic Chemistry ,symbols.namesake ,0103 physical sciences ,Monolayer ,Materials Chemistry ,symbols ,Direct and indirect band gaps ,van der Waals force ,010306 general physics ,0210 nano-technology ,High-resolution transmission electron microscopy - Abstract
Large area MoS2 and WS2 van der Waals epitaxial thin films with control over number of layers including monolayer is grown by pulsed laser deposition utilizing slower growth kinetics. The films grown on c-plane sapphire show stiffening of A(1g) and E-2g(1) phonon modes with decreasing number of layers for both MoS2 and WS2. The observed stiffening translate into the compressive strain of 0.52% & 0.53% with accompanying increase in fundamental direct band gap to 1.74 and 1.68 eV for monolayer MoS2 and WS2, respectively. The strain decays with the number of layers. HRTEM imaging directly reveals the nature of atomic registry of van der Waals layers with the substrate and the associated compressive strain. The results demonstrate a practical route to stabilize and engineer strain for this class of material over large area device fabrication. (C) 2017 Elsevier B.V. All rights reserved.
- Published
- 2017