title: Band gap engineering and layer-by-layer mapping of selenium-doped molybdenum disulfide.
abstract: Ternary two-dimensional dichalcogenide alloys exhibit compositionally modulated electronic structure, and hence, control of dopant concentration within each individual layer of these compounds provides a powerful tool to efficiently modify their physical and chemical properties. The main challenge arises when quantifying and locating the dopant atoms within each layer in order to better understand and fine-tune the desired properties. Here we report the synthesis of molybdenum disulfide substitutionally doped with a broad range of selenium concentrations, resulting in over 10% optical band gap modulations in atomic layers. Chemical analysis using Z-contrast imaging provides direct maps of the dopant atom distribution in individual MoS2 layers and hence a measure of the local optical band gaps. Furthermore, in a bilayer structure, the dopant distribution is imaged layer-by-layer. This work demonstrates that each layer in the bilayer system contains similar local Se concentrations, randomly distributed, providing new insights into the growth mechanism and alloying behavior in two-dimensional dichalcogenide atomic layers. The results show that growth of uniform, ternary, two-dimensional dichalcogenide alloy films with tunable electronic properties is feasible.
authors.affiliation: Department of Chemistry, Rice University , Houston, Texas 77005, United States.
authors.forename: Yongji
authors.initials: Y
authors.lastname: Gong
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Lupini
authors.forename: Gang
authors.initials: G
authors.lastname: Shi
authors.forename: Junhao
authors.initials: J
authors.lastname: Lin
authors.forename: Sina
authors.initials: S
authors.lastname: Najmaei
authors.forename: Zhong
authors.initials: Z
authors.lastname: Lin
authors.forename: Ana Laura
authors.initials: AL
authors.lastname: Elías
authors.forename: Ayse
authors.initials: A
authors.lastname: Berkdemir
authors.forename: Ge
authors.initials: G
authors.lastname: You
authors.forename: Humberto
authors.initials: H
authors.lastname: Terrones
authors.forename: Mauricio
authors.initials: M
authors.lastname: Terrones
authors.forename: Robert
authors.initials: R
authors.lastname: Vajtai
authors.forename: Sokrates T
authors.initials: ST
authors.lastname: Pantelides
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Pennycook
authors.forename: Jun
authors.initials: J
authors.lastname: Lou
authors.forename: Wu
authors.initials: W
authors.lastname: Zhou
authors.forename: Pulickel M
authors.initials: PM
authors.lastname: Ajayan