Anomalous Raman and photoluminescence blue shift in mono- and a few layered pulsed laser deposited MoS2 thin films. (June 2018)

• Record Type: Journal Article
• Authors: Pradhan, Gobinda; Sharma, Ashwini Kumar
• Is Part Of: Materials research bulletin. Volume 102(2018)
• Page Start: 406
• Page End: 411
• Publication Date: 2018-06
• Subjects: A. Layered compounds -- A. Thin film -- B. Laser deposition -- C. Raman spectroscopy -- C. Transmission electron microscopy; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2018.03.001
• Languages: English
• ISSNs: 0025-5408

Abstract

Graphical abstract: Highlights: Mono- and a few layered MoS2 films deposited using pulsed laser deposition technique by varying the deposition time. The films experienced an epitaxial compression due to its adhesion with the substrate. Lattice strain of the films led to a significant Raman frequency shift. An anomalous PL peak was observed which is attributed to quantum confinement. Abstract: We report on the Raman blue shift of layered MoS2 films as well as an anomalous blue shift of the photoluminescence spectra of nanocrystallite MoS2 films grown by pulsed laser deposition. Monolayer, bilayer and trilayer MoS2 films were fabricated by ablating MoS2 target for a deposition time of around 14, 24 and 30 s at a laser fluence of 2.2 Jcm −2 . The two Raman active modes showed lattice strain-induced blue shift of 1–3 cm −1 . The layered films showed an out-of-plane compressive strain as well as an in-plane tensile strain confirmed by Riet-Veld refinement of the X-ray diffraction pattern. TEM image of the MoS2 film for 14 s demonstrated the presence of nanocrystallites of an average size of 13 nm along with the layered film of MoS2 . An anomalous photoluminescence peak was observed corresponding to the MoS2 nanocrystallites at 2.18 eV, attributed to quantum confinement effect.