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Li Y, Wang T, Wang H, Li Z, Chen Y, West D, Sankar R, Ulaganathan RK, Chou F, Wetzel C, Xu CY, Zhang S, Shi SF. Enhanced Light Emission from the Ridge of Two-Dimensional InSe Flakes. NANO LETTERS 2018; 18:5078-5084. [PMID: 30021441 DOI: 10.1021/acs.nanolett.8b01940] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
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 thin layers and is drastically different from transition-metal dichalcogenides, 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 ∼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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Affiliation(s)
- Yang Li
- School of Materials Science and Engineering , Harbin Institute of Technology , Harbin 150001 , China
| | | | | | - Zhipeng Li
- School of Chemistry and Chemical Engineering , Shanghai Jiao Tong University , Shanghai 200240 , China
| | | | | | - Raman Sankar
- Institute of Physics , Academia Sinica , Nangang, Taipei , Taiwan 11529 , Taiwan
- Center for Condensed Matter Science , National Taiwan University , Taipei , Taiwan 10617 , Taiwan
| | - Rajesh K Ulaganathan
- Institute of Physics , Academia Sinica , Nangang, Taipei , Taiwan 11529 , Taiwan
- Center for Condensed Matter Science , National Taiwan University , Taipei , Taiwan 10617 , Taiwan
| | - Fangcheng Chou
- Institute of Physics , Academia Sinica , Nangang, Taipei , Taiwan 11529 , Taiwan
- Center for Condensed Matter Science , National Taiwan University , Taipei , Taiwan 10617 , Taiwan
| | | | - Cheng-Yan Xu
- School of Materials Science and Engineering , Harbin Institute of Technology , Harbin 150001 , China
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Antonius G, Qiu DY, Louie SG. Orbital Symmetry and the Optical Response of Single-Layer MX Monochalcogenides. NANO LETTERS 2018; 18:1925-1929. [PMID: 29465238 DOI: 10.1021/acs.nanolett.7b05286] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We show that the absorption spectra of single-layer GaSe and GaTe in the hexagonal phase feature exciton peaks with distinct polarization selectivity. We investigate these distinct features from first-principles calculations using the GW-BSE formalism. We show that, because of the symmetry of the bands under in-plane mirror symmetry, the bound exciton states selectively couple to either in-plane or out-of-plane polarization of the light. In particular, for a p-polarized light absorption experiment, the absorption peaks of the hydrogenic s-like excitons emerge at large angle of incidence, while the overall absorbance reduces over the rest of the spectrum.
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Affiliation(s)
- Gabriel Antonius
- Department of Physics , University of Californi at Berkeley , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Diana Y Qiu
- Department of Physics , University of Californi at Berkeley , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Steven G Louie
- Department of Physics , University of Californi at Berkeley , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
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Ku SA, Chu WC, Luo CW, Andreev YM, Lanskii G, Shaidukoi A, Izaak T, Svetlichnyi V, Wu KH, Kobayashi T. Optimal Te-doping in GaSe for non-linear applications. OPTICS EXPRESS 2012; 20:5029-5037. [PMID: 22418307 DOI: 10.1364/oe.20.005029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Centimeter-sized Te-doped GaSe ingots were grown from the charge compositions of GaSe with nominals 0.05, 0.1, 0.5, 1, and 3 mass% Te, which were identified as ε-GaSe:Te (0.01, 0.07, 0.38, 0.67, and 2.07 mass%) single crystals. The evolution of the absorption peaks of the phonon modes E'(2) (≈ 0.584 THz) and E"(2) (1.77 THz) on Te-doping in GaSe:Te crystals was studied by THz time-domain spectroscopy. This study proposes that the evolution of both E'(2) and E''(2) absorption peaks correlates well with the optical quality of Te-doped GaSe crystals, which was confirmed by experimental results on the efficiency of THz generation by optical rectification. Maximal intensity of the absorption peak of the rigid layer mode E'(2) is proposed as a criterion for identification of optimal Te-doping in GaSe crystals.
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Affiliation(s)
- Shin An Ku
- Department of Electrophysics, National Chiao-Tung University, Hsinchu, Taiwan
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Balzarotti A, Picozzi P, Santucci S. Effects of anisotropy on the electroreflectance spectra ofGaSe at oblique incidence. ACTA ACUST UNITED AC 2007. [DOI: 10.1007/bf02723485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Seyhan A, Karabulut O, Akįnoğlu BG, Aslan B, Turan R. Optical anisotropy in GaSe. CRYSTAL RESEARCH AND TECHNOLOGY 2005. [DOI: 10.1002/crat.200410452] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Giorgianni U, Mondio G, Perillo P, Saitta G, Vermiglio G. Infrared and UV-visible spectra of layer semiconductors Gas, GaSe and GaTe. ACTA ACUST UNITED AC 1977. [DOI: 10.1051/jphys:0197700380100129300] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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