Journal
ACS NANO
Volume 16, Issue 5, Pages 7428-7437Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.1c09809
Keywords
WS2; nitrogen plasma; substitution; photoluminescence; first-principles calculations
Categories
Funding
- National Science Foundation [ECCS-1943895]
- U.S. DOE, Office of Basic Energy Sciences [DE-AC02-06CH11357]
- Center for Nanophase Materials Sciences (CNMS), US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory
- NSF [DMR-1539916, DMR-2039351]
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The electronic and optical properties of two-dimensional materials can be altered by defects. In this study, defects created by remote plasma exposure in single-layer WS2 induce a distinct low-energy photoluminescence peak at 1.59 eV. This peak is caused by sulfur substitutions by nitrogen.
The electronic and optical properties of two-dimensional materials can be strongly influenced by defects, some of which can find significant implementations, such as controllable doping, prolonged valley lifetime, and single-photon emissions. In this work, we demonstrate that defects created by remote N-2 plasma exposure in single-layer WS2 can induce a distinct low-energy photoluminescence (PL) peak at 1.59 eV, which is in sharp contrast to that caused by remote Ar plasma. This PL peak has a critical requirement on the N-2 plasma exposure dose, which is strongest for WS2 with about 2.0% sulfur deficiencies (including substitutions and vacancies) and vanishes at 5.6% or higher sulfur deficiencies. Both experiments and first-principles calculations suggest that this 1.59 eV PL peak is caused by defects related to the sulfur substitutions by nitrogen, even though low-temperature PL measurements also reveal that not all the sulfur vacancies are remedied by the substitutional nitrogen. The distinct low-energy PL peak suggests that the substitutional nitrogen defect in single-layer WS2 can potentially serve as an isolated artificial atom for creating single-photon emitters, and its intensity can also be used to monitor the doping concentrations of substitutional nitrogen.
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