title: The Effect of Preparation Conditions on Raman and Photoluminescence of Monolayer WS2.
abstract: We report on preparation dependent properties observed in monolayer WS2samples synthesized via chemical vapor deposition (CVD) on a variety of common substrates (Si/SiO2, sapphire, fused silica) as well as samples that were transferred from the growth substrate onto a new substrate. The as-grown CVD materials (as-WS2) exhibit distinctly different optical properties than transferred WS2(x-WS2). In the case of CVD growth on Si/SiO2, following transfer to fresh Si/SiO2there is a ~50 meV shift of the ground state exciton to higher emission energy in both photoluminescence emission and optical reflection. This shift is indicative of a reduction in tensile strain by ~0.25%. Additionally, the excitonic state in x-WS2is easily modulated between neutral and charged exciton by exposure to moderate laser power, while such optical control is absent in as-WS2for all growth substrates investigated. Finally, we observe dramatically different laser power-dependent behavior for as-grown and transferred WS2. These results demonstrate a strong sensitivity to sample preparation that is important for both a fundamental understanding of these novel materials as well as reliable reproduction of device properties.
authors.affiliation: Naval Research Laboratory, Washington DC 20375, USA.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: McCreary
authors.affiliation: Naval Research Laboratory, Washington DC 20375, USA.
authors.forename: Aubrey T
authors.initials: AT
authors.lastname: Hanbicki
authors.affiliation: Department of Physics, The Ohio State University, Columbus OH 43210, USA.
authors.forename: Simranjeet
authors.initials: S
authors.lastname: Singh
authors.affiliation: Department of Physics, The Ohio State University, Columbus OH 43210, USA.
authors.forename: Roland K
authors.initials: RK
authors.lastname: Kawakami
authors.affiliation: Naval Research Laboratory, Washington DC 20375, USA.
authors.forename: Glenn G
authors.initials: GG
authors.lastname: Jernigan
authors.affiliation: Department of Physics and Nanoscience Technology Center, University of Central Florida, Orlando, FL 32816-2385, USA.
authors.forename: Masa
authors.initials: M
authors.lastname: Ishigami
authors.affiliation: Naval Research Laboratory, Washington DC 20375, USA.
authors.forename: Amy
authors.initials: A
authors.lastname: Ng
authors.affiliation: Naval Research Laboratory, Washington DC 20375, USA.
authors.forename: Todd H
authors.initials: TH
authors.lastname: Brintlinger
authors.affiliation: Naval Research Laboratory, Washington DC 20375, USA.
authors.forename: Rhonda M
authors.initials: RM
authors.lastname: Stroud
authors.affiliation: Naval Research Laboratory, Washington DC 20375, USA.
authors.forename: Berend T
authors.initials: BT
authors.lastname: Jonker