title: Photoluminescence Enhancement and Structure Repairing of Monolayer MoSe2 by Hydrohalic Acid Treatment.
abstract: Atomically thin two-dimensional transition-metal dichalcogenides (TMDCs) have attracted much attention recently due to their unique electronic and optical properties for future optoelectronic devices. The chemical vapor deposition (CVD) method is able to generate TMDCs layers with a scalable size and a controllable thickness. However, the TMDC monolayers grown by CVD may incorporate structural defects, and it is fundamentally important to understand the relation between photoluminescence and structural defects. In this report, point defects (Se vacancies) and oxidized Se defects in CVD-grown MoSe2 monolayers are identified by transmission electron microscopy and X-ray photoelectron spectroscopy. These defects can significantly trap free charge carriers and localize excitons, leading to the smearing of free band-to-band exciton emission. Here, we report that the simple hydrohalic acid treatment (such as HBr) is able to efficiently suppress the trap-state emission and promote the neutral exciton and trion emission in defective MoSe2 monolayers through the p-doping process, where the overall photoluminescence intensity at room temperature can be enhanced by a factor of 30. We show that HBr treatment is able to activate distinctive trion and free exciton emissions even from highly defective MoSe2 layers. Our results suggest that the HBr treatment not only reduces the n-doping in MoSe2 but also reduces the structural defects. The results provide further insights of the control and tailoring the exciton emission from CVD-grown monolayer TMDCs.
authors.affiliation: Physical Sciences and Engineering Division, King Abdullah University of Science and Technology , Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Hau-Vei
authors.initials: HV
authors.lastname: Han
authors.affiliation: Physical Sciences and Engineering Division, King Abdullah University of Science and Technology , Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Ang-Yu
authors.initials: AY
authors.lastname: Lu
authors.forename: Li-Syuan
authors.initials: LS
authors.lastname: Lu
authors.affiliation: Physical Sciences and Engineering Division, King Abdullah University of Science and Technology , Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Jing-Kai
authors.initials: JK
authors.lastname: Huang
authors.affiliation: Physical Sciences and Engineering Division, King Abdullah University of Science and Technology , Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Henan
authors.initials: H
authors.lastname: Li
authors.affiliation: Research Center for Applied Sciences , 128 Sec. 2, Academia Road, Nankang, Taipei 11529, Taiwan.
authors.forename: Chang-Lung
authors.initials: CL
authors.lastname: Hsu
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba 305-8560, Japan.
authors.forename: Yung-Chang
authors.initials: YC
authors.lastname: Lin
authors.affiliation: Physical Sciences and Engineering Division, King Abdullah University of Science and Technology , Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Chiu
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba 305-8560, Japan.
authors.forename: Kazu
authors.initials: K
authors.lastname: Suenaga
authors.affiliation: Research Center for Applied Sciences , 128 Sec. 2, Academia Road, Nankang, Taipei 11529, Taiwan.
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Chu
authors.forename: Hao-Chung
authors.initials: HC
authors.lastname: Kuo
authors.affiliation: Taiwan Consortium of Emergent Crystalline Materials (TCECM), Ministry of Science and Technology , Hsinchu 300, Taiwan.
authors.forename: Wen-Hao
authors.initials: WH
authors.lastname: Chang
authors.affiliation: Physical Sciences and Engineering Division, King Abdullah University of Science and Technology , Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Lain-Jong
authors.initials: LJ
authors.lastname: Li
authors.affiliation: Physical Sciences and Engineering Division, King Abdullah University of Science and Technology , Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Yumeng
authors.initials: Y
authors.lastname: Shi
keywords: layered materials; molybdenum diselenide; photoluminescence; transition-metal dichalcogenides; two-dimensional materials