Tunable Photoluminescence of Atomically Thin MoS 2 via Nb Doping
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.24
Tunable Photoluminescence of Atomically Thin MoS2 via Nb Doping Gourav Bhowmik1,2, Katherine Gruenewald1, Girish Malladi1, Tyler Mowll1, Carl Ventrice Jr.1 and Mengbing Huang1 1
Colleges of Nanoscale Science and Engineering, SUNY Polytechnic Institute, 257 Fuller Road, Albany, NY 12203, U.S.A.
2
Ion Beam Laboratory, University at Albany, SUNY, 1400 Washington Ave, Albany, NY 12222, U.S.A.
ABSTRACT
The emergence of 2D materials has led to increased attention on correlating the structural, optical, and optoelectronic properties of atomically thin transition metal chalcogenides like MoS2. We demonstrate the tunability of the photoluminescence (PL) properties of bulk MoS2 via implantation of Nb ions. Raman spectroscopy is used to confirm the p-type doping. The PL intensity of MoS2 is drastically enhanced by the adsorption of p-type dopants. X-ray photoelectron spectroscopy (XPS) is used to study the change of MoS2 structure postimplantation. Our results provide a new route for modulating the optical properties of twodimensional semiconductors. The strong and stable PL from defect sites of MoS2 created by Nb ion implantation may have promising applications in optoelectronic devices.
INTRODUCTION Atomically thin sheets of layered transition metal dichalcogenides (LTMDs), such as MoS2, WSe2, MoTe2, etc., represent an emerging class of materials with application in next-generation electrical [1] and optoelectronic [2] devices. Devices including field effect transistors (FETs) with excellent on/off ratio and high current densities, [1] as well as integrated circuits [3] have been reported using flakes of MoS2 mechanically exfoliated from bulk geological samples. Molybdenum disulfide (MoS2), a well-known LTMD, is an indirect band gap semiconductor with an energy gap of ∼1.2 eV in the bulk form [4] which increases with decreasing crystal thickness below 100 nm due to quantum confinement and calculations predict it to reach 1.9 eV for a single
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monolayer. [5] Additionally, the nature of the band gap also changes from indirect to direct when the thickness reaches a single monolayer. [5] Recent success in isolating monolayers of MoS2 has allowed the observation of strong photoluminescence that can be attributed to the direct gap electronic structure of monolayer MoS2. [6] Exfoliation of MoS2 into individual monolayers is a critical step toward making it optically active and implementing into novel devices. For practical applications, a scalable and controlled deposition technique is required. Ion implantation is one such technique that may just allow isolation of already weak van der Waals bonded layers in LTMDs into atomically thin layers. The use of Niobium (Nb) has been reported to be employed as a substitutional
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