Controlling neutral and charged excitons in MoS₂ with defects

Journal Article · 12 January 2020 · Journal of Materials Research

DOI: https://doi.org/10.1557/jmr.2019.404 · OSTI ID:1656832

Burns, Kory ^[1]; Tan, Anne Marie Z. ^[1]; Gabriel, Adam ^[2]; Shao, Lin ^[2]; Hennig, Richard G. ^[1]; Aitkaliyeva, Assel  ^[1]

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1. University of Florida, Gainesville, FL (United States)
2. Texas A & M University, College Station, TX (United States)

In this contribution, we use heavy ion irradiation and photoluminescence (PL) spectroscopy to demonstrate that defects can be used to tailor the optical properties of two-dimensional molybdenum disulfide (MoS₂). Sonicated MoS₂ flakes were deposited onto Si/SiO₂ substrate and subjected to 3 MeV Au²⁺ ion irradiation at room temperature to fluences ranging from 1 × 10¹² to 1 × 10¹⁶ cm^–2. We demonstrate that irradiation-induced defects can control optical excitations in the inner core shell of MoS₂ by binding A_1s- and B_1s-excitons, and correlate the exciton peaks to the specific defects introduced with irradiation. The systematic increase of ion fluence produced different defect densities in MoS₂, which were estimated using B/A exciton ratios and progressively increased with ion fluence. We show that up to the fluences of 1 × 10¹⁴ cm^–2, the MoS₂ lattice remains crystalline and defect densities can be controlled, whereas at higher fluences (≥1 × 10¹⁵ cm^–2), the large number of introduced defects distorts the excitonic structure of the material. In addition to controlling excitons, defects were used to split bound and free trions, and we demonstrate that at higher fluences (1 × 10¹⁵ cm^–2), both free and bound trions can be observed in the same PL spectrum. Most importantly, the lifetimes of these states exceed trion and exciton lifetimes in pristine MoS₂, and PL spectra of irradiated MoS₂ remains unchanged weeks after irradiation experiments. Thus, this work demonstrated the feasibility of engineering novel optical behaviors in low-dimensional materials using heavy ion irradiation. The insights gained from this study will aid in understanding the many-body interactions in low-dimensional materials and may ultimately be used to develop novel materials for optoelectronic applications.

• Research Organization: University of Florida, Gainesville, FL (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0019014
• OSTI ID: 1656832
• Journal Information: Journal of Materials Research, Journal Name: Journal of Materials Research Journal Issue: 8 Vol. 35; ISSN 0884-2914
• Publisher: Materials Research SocietyCopyright Statement
• Country of Publication: United States
• Language: English