title: Tailoring Vacancies Far Beyond Intrinsic Levels Changes the Carrier Type and Optical Response in Monolayer MoSe2-x Crystals.
abstract: Defect engineering has been a critical step in controlling the transport characteristics of electronic devices, and the ability to create, tune, and annihilate defects is essential to enable the range of next-generation devices. Whereas defect formation has been well-demonstrated in three-dimensional semiconductors, similar exploration of the heterogeneity in atomically thin two-dimensional semiconductors and the link between their atomic structures, defects, and properties has not yet been extensively studied. Here, we demonstrate the growth of MoSe2-x single crystals with selenium (Se) vacancies far beyond intrinsic levels, up to ∼20%, that exhibit a remarkable transition in electrical transport properties from n- to p-type character with increasing Se vacancy concentration. A new defect-activated phonon band at ∼250 cm(-1) appears, and the A1g Raman characteristic mode at 240 cm(-1) softens toward ∼230 cm(-1) which serves as a fingerprint of vacancy concentration in the crystals. We show that post-selenization using pulsed laser evaporated Se atoms can repair Se-vacant sites to nearly recover the properties of the pristine crystals. First-principles calculations reveal the underlying mechanisms for the corresponding vacancy-induced electrical and optical transitions.
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Masoud
authors.initials: M
authors.lastname: Mahjouri-Samani
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Liangbo
authors.initials: L
authors.lastname: Liang
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee , Knoxville, Tennessee 37996, United States.
authors.forename: Akinola
authors.initials: A
authors.lastname: Oyedele
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Korea Research Institute of Standards and Science , Daejeon 305-340, Korea.|Department of Nano Science, Korea University of Science and Technology , Daejeon 305-350, Korea.
authors.forename: Yong-Sung
authors.initials: YS
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.
authors.forename: Mengkun
authors.initials: M
authors.lastname: Tian
authors.affiliation: Department of Materials Science and Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Cross
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Lin
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Abdelaziz
authors.initials: A
authors.lastname: Boulesbaa
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Rouleau
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Puretzky
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: Xiao
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Mina
authors.initials: M
authors.lastname: Yoon
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Gyula
authors.initials: G
authors.lastname: Eres
authors.affiliation: Department of Materials Science and Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.|Materials Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Gerd
authors.initials: G
authors.lastname: Duscher
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Bobby G
authors.initials: BG
authors.lastname: Sumpter
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: David B
authors.initials: DB
authors.lastname: Geohegan
keywords: Raman scattering; Transitional metal dichalcogenides; electrical properties; optical properties; vacancies