Journal
NANO LETTERS
Volume 18, Issue 8, Pages 5078-5084Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.8b01940
Keywords
Indium selenide; ridges; selection rules; defect emission; stark effect
Categories
Funding
- AFOSR [FA9550-18-1-0312]
- U.S. DOE [DESC0002623]
- NSF [EFMA-1542798]
- NERSC under DOE [DE-AC02-05CH11231]
- CCI at RPI
- National Natural Science Foundation of China [51572057]
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InSe, a newly rediscovered two-dimensional (2D) semiconductor, possesses superior electrical and optical properties as a direct-band-gap semiconductor with high mobility from bulk to atomically thm layers and is drastically different from transition-metal dichalcogemdes, in which the direct band gap only exists at the single-layer limit. However, absorption in InSe is mostly dominated by an out-of-plane dipole contribution, which results in the limited absorption of normally incident light that can only excite the in-plane dipole at resonance. To address this challenge, we have explored a unique geometric ridge state of the 2D flake without compromising the sample quality. We observed the enhanced absorption at the ridge over a broad range of excitation frequencies from photocurrent and photoluminescence (PL) measurements. In addition, we have discovered new PL peaks at low temperatures due to defect states on the ridge, which can be as much as similar to 60 times stronger than the intrinsic PL peak of InSe. Interestingly, the PL of the defects is highly tunable through an external electrical field, which can be attributed to the Stark effect of the localized defects. InSe ridges thus provide new avenues for manipulating light-matter interactions and defect engineering that are vitally crucial for novel optoelectronic devices based on 2D semiconductors.
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