title: Extraordinary room-temperature photoluminescence in triangular WS2 monolayers.
abstract: Individual monolayers of metal dichalcogenides are atomically thin two-dimensional crystals with attractive physical properties different from those of their bulk counterparts. Here we describe the direct synthesis of WS2 monolayers with triangular morphologies and strong room-temperature photoluminescence (PL). The Raman response as well as the luminescence as a function of the number of S-W-S layers is also reported. The PL weakens with increasing number of layers due to a transition from direct band gap in a monolayer to indirect gap in multilayers. The edges of WS2 monolayers exhibit PL signals with extraordinary intensity, around 25 times stronger than that at the platelet's center. The structure and chemical composition of the platelet edges appear to be critical for PL enhancement.
authors.affiliation: Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
authors.forename: Humberto R
authors.initials: HR
authors.lastname: Gutiérrez
authors.forename: Nestor
authors.initials: N
authors.lastname: Perea-López
authors.forename: Ana Laura
authors.initials: AL
authors.lastname: Elías
authors.forename: Ayse
authors.initials: A
authors.lastname: Berkdemir
authors.forename: Bei
authors.initials: B
authors.lastname: Wang
authors.forename: Ruitao
authors.initials: R
authors.lastname: Lv
authors.forename: Florentino
authors.initials: F
authors.lastname: López-Urías
authors.forename: Vincent H
authors.initials: VH
authors.lastname: Crespi
authors.forename: Humberto
authors.initials: H
authors.lastname: Terrones
authors.forename: Mauricio
authors.initials: M
authors.lastname: Terrones