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Sharma A, Zhu Y, Halbich R, Sun X, Zhang L, Wang B, Lu Y. Engineering the Dynamics and Transport of Excitons, Trions, and Biexcitons in Monolayer WS 2. ACS Appl Mater Interfaces 2022; 14:41165-41177. [PMID: 36048513 DOI: 10.1021/acsami.2c08199] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The study of transport and diffusion dynamics of quasi-particles such as excitons, trions, and biexcitons in two-dimensional (2D) semiconductors has opened avenues for their application in high-speed excitonic and optoelectronic devices. However, long-range transport and fast diffusion of these quasi-particles have not been reported for 2D systems such as transition metal dichalcogenides (TMDCs). The reported diffusion coefficients from TMDCs are low, limiting their use in high-speed excitonic devices and other optoelectronic applications. Here, we report the highest exciton diffusion coefficient value in monolayer WS2 achieved via engineering the radiative lifetime and diffusion lengths using static back-gate voltage and substrate engineering. Electrostatic doping is observed to modulate the radiative lifetime and in turn the diffusion coefficient of excitons by ∼three times at room temperature. By combining electrostatic doping and substrate engineering, we push the diffusion coefficient to an extremely high value of 86.5 cm2/s, which has not been reported before in TMDCs and is even higher than the values in some 1D systems. At low temperatures, we further report the control of dynamic and spatial diffusion of excitons, trions, and biexcitons from WS2. The electrostatic control of dynamics and transport of these quasi-particles in monolayers establishes monolayer TMDCs as ideal candidates for high-speed excitonic circuits, optoelectronic, and photonic device applications.
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Affiliation(s)
- Ankur Sharma
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Yi Zhu
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Robert Halbich
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Xueqian Sun
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Linglong Zhang
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Bowen Wang
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Yuerui Lu
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
- ARC Centre of Excellence in Quantum Computation and Communication Technology ANU Node, Canberra, ACT 2601, Australia
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Abstract
We demonstrate robust optical bistability, the phenomenon of two well-discriminated stable states depending upon the history of the optical input, in fully suspended monolayers of WSe2 at low temperatures near the exciton resonance. Optical bistability has been achieved under continuous-wave optical excitation that is red-detuned from the exciton resonance at an intensity level of 103 W/cm2. The observed bistability is originated from a photothermal mechanism, which provides both optical nonlinearity and passive feedback, two essential elements for optical bistability. The low thermal conductance of suspended samples is primarily responsible for the low excitation intensities required for optical bistability. Under a finite out-of-plane magnetic field, the exciton bistability becomes helicity dependent due to the exciton valley Zeeman effect, which enables repeatable switching of the sample reflectance by light polarization. Our study has opened up exciting opportunities in controlling light with light, including its wavelength, power, and polarization, using monolayer semiconductors.
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Affiliation(s)
- Hongchao Xie
- Laboratory of Atomic and Solid State Physics and School of Applied and Engineering Physics , Cornell University , Ithaca , New York 14853 , United States
- Department of Physics , Penn State University , University Park , Pennsylvania 16802 , United States
| | - Shengwei Jiang
- Laboratory of Atomic and Solid State Physics and School of Applied and Engineering Physics , Cornell University , Ithaca , New York 14853 , United States
| | - Jie Shan
- Laboratory of Atomic and Solid State Physics and School of Applied and Engineering Physics , Cornell University , Ithaca , New York 14853 , United States
- Kavli Institute at Cornell for Nanoscale Science , Ithaca , New York 14853 , United States
| | - Kin Fai Mak
- Laboratory of Atomic and Solid State Physics and School of Applied and Engineering Physics , Cornell University , Ithaca , New York 14853 , United States
- Kavli Institute at Cornell for Nanoscale Science , Ithaca , New York 14853 , United States
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