1
|
Gauriot N, Ashoka A, Lim J, See ST, Sung J, Rao A. Direct Imaging of Carrier Funneling in a Dielectric Engineered 2D Semiconductor. ACS NANO 2024; 18:264-271. [PMID: 38196169 PMCID: PMC10786151 DOI: 10.1021/acsnano.3c05957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 11/23/2023] [Accepted: 12/01/2023] [Indexed: 01/11/2024]
Abstract
In atomically thin transition-metal dichalcogenides (TMDCs), the environmental sensitivity of the strong Coulomb interaction offers promising approaches to create spatially varying potential landscapes in the same continuous material by tuning its dielectric environment. Thus, allowing for control of transport. However, a scalable and CMOS-compatible method for achieving this is required to harness these effects in practical applications. In addition, because of their ultrashort lifetime, observing the spatiotemporal dynamics of carriers in monolayer TMDCs, on the relevant time scale, is challenging. Here, we pattern and deposit a thin film of hafnium oxide (HfO2) via atomic layer deposition (ALD) on top of a monolayer of WSe2. This allows for the engineering of the dielectric environment of the monolayer and design of heterostructures with nanoscale spatial resolution via a highly scalable postsynthesis methodology. We then directly image the transport of photoexcitations in the monolayer with 50 fs time resolution and few-nanometer spatial precision, using a pump probe microscopy technique. We observe the unidirectional funneling of charge carriers, from the unpatterned to the patterned areas, over more than 50 nm in the first 20 ps with velocities of over 2 × 103 m/s at room temperature. These results demonstrate the possibilities offered by dielectric engineering via ALD patterning, allowing for arbitrary spatial patterns that define the potential landscape and allow for control of the transport of excitations in atomically thin materials. This work also shows the power of the transient absorption methodology to image the motion of photoexcited states in complex potential landscapes on ultrafast time scales.
Collapse
Affiliation(s)
- Nicolas Gauriot
- Cavendish
Laboratory, University of Cambridge, CB3 0HE Cambridge, United Kingdom
| | - Arjun Ashoka
- Cavendish
Laboratory, University of Cambridge, CB3 0HE Cambridge, United Kingdom
| | - Juhwan Lim
- Cavendish
Laboratory, University of Cambridge, CB3 0HE Cambridge, United Kingdom
| | - Soo Teck See
- Cavendish
Laboratory, University of Cambridge, CB3 0HE Cambridge, United Kingdom
| | - Jooyoung Sung
- Cavendish
Laboratory, University of Cambridge, CB3 0HE Cambridge, United Kingdom
- Department
of Physics and Chemistry, DGIST, Daegu 42988, Republic of Korea
| | - Akshay Rao
- Cavendish
Laboratory, University of Cambridge, CB3 0HE Cambridge, United Kingdom
| |
Collapse
|
2
|
Tenney SM, Tan LA, Tan X, Sonnleitner ML, Coffey B, Williams JA, Ronquillo R, Atallah TL, Ahmed T, Caram JR. Efficient 2D to 0D Energy Transfer in HgTe Nanoplatelet-Quantum Dot Heterostructures through High-Speed Exciton Diffusion. J Phys Chem Lett 2023; 14:9456-9463. [PMID: 37830914 DOI: 10.1021/acs.jpclett.3c02168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
Large area absorbers with localized defect emission are of interest for energy concentration via the antenna effect. Transfer between 2D and 0D quantum-confined structures is advantageous as it affords maximal lateral area antennas with continuously tunable emission. We report the quantum efficiency of energy transfer in in situ grown HgTe nanoplatelet (NPL)/quantum dot (QD) heterostructures to be near unity (>85%), while energy transfer in separately synthesized and well separated solutions of HgTe NPLs to QDs only reaches 47 ± 11% at considerably higher QD concentrations. Using Kinetic Monte Carlo simulations, we estimate an exciton diffusion constant of 1-10 cm2/s in HgTe NPLs, the same magnitude as that of 2D semiconductors. We also simulate in-solution energy transfer between NPLs and QDs, recovering an R-4 dependence consistent with 2D-0D near-field energy transfer even in randomly distributed NPL/QD mixtures. This highlights the advantage of NPLs 2D morphology and the efficiency of NPL/QD heterostructures and mixtures for energy harvesting.
Collapse
Affiliation(s)
- Stephanie M Tenney
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
| | - Lauren A Tan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
| | - Xuanheng Tan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
| | - Mikayla L Sonnleitner
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
| | - Belle Coffey
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
| | - Jillian A Williams
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
| | - Ricky Ronquillo
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
| | - Timothy L Atallah
- Department of Chemistry and Biochemistry, Denison University, 500 West Loop, Granville, Ohio 43023, United States
| | - Tasnim Ahmed
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
| | - Justin R Caram
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
| |
Collapse
|
3
|
Zhu G, Zhang L, Li W, Shi X, Zou Z, Guo Q, Li X, Xu W, Jie J, Wang T, Du W, Xiong Q. Room-temperature high-speed electrical modulation of excitonic distribution in a monolayer semiconductor. Nat Commun 2023; 14:6701. [PMID: 37872139 PMCID: PMC10593816 DOI: 10.1038/s41467-023-42568-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Accepted: 10/16/2023] [Indexed: 10/25/2023] Open
Abstract
Excitons in monolayer semiconductors, benefitting from their large binding energies, hold great potential towards excitonic circuits bridging nano-electronics and photonics. However, achieving room-temperature ultrafast on-chip electrical modulation of excitonic distribution and flow in monolayer semiconductors is nontrivial. Here, utilizing lateral bias, we report high-speed electrical modulation of the excitonic distribution in a monolayer semiconductor junction at room temperature. The alternating charge trapping/detrapping at the two monolayer/electrode interfaces induces a non-uniform carrier distribution, leading to controlled in-plane spatial variations of excitonic populations, and mimicking a bias-driven excitonic flow. This modulation increases with the bias amplitude and eventually saturates, relating to the energetic distribution of trap density of states. The switching time of the modulation is down to 5 ns, enabling high-speed excitonic devices. Our findings reveal the trap-assisted exciton engineering in monolayer semiconductors and offer great opportunities for future two-dimensional excitonic devices and circuits.
Collapse
Affiliation(s)
- Guangpeng Zhu
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Lan Zhang
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Wenfei Li
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Xiuqi Shi
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Zhen Zou
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Qianqian Guo
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Xiang Li
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Weigao Xu
- Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, PR China
| | - Jiansheng Jie
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Tao Wang
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China.
| | - Wei Du
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China.
| | - Qihua Xiong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, PR China
- Frontier Science Center for Quantum Information, Beijing, 100084, PR China
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, PR China
- Collaborative Innovation Center of Quantum Matter, Beijing, PR China
| |
Collapse
|
4
|
Weaver H, Went CM, Wong J, Jasrasaria D, Rabani E, Atwater HA, Ginsberg NS. Detecting, Distinguishing, and Spatiotemporally Tracking Photogenerated Charge and Heat at the Nanoscale. ACS NANO 2023; 17:19011-19021. [PMID: 37721430 PMCID: PMC10569093 DOI: 10.1021/acsnano.3c04607] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 09/13/2023] [Indexed: 09/19/2023]
Abstract
Since dissipative processes are ubiquitous in semiconductors, characterizing how electronic and thermal energy transduce and transport at the nanoscale is vital for understanding and leveraging their fundamental properties. For example, in low-dimensional transition metal dichalcogenides (TMDCs), excess heat generation upon photoexcitation is difficult to avoid since even with modest injected exciton densities exciton-exciton annihilation still occurs. Both heat and photoexcited electronic species imprint transient changes in the optical response of a semiconductor, yet the distinct signatures of each are difficult to disentangle in typical spectra due to overlapping resonances. In response, we employ stroboscopic optical scattering microscopy (stroboSCAT) to simultaneously map both heat and exciton populations in few-layer MoS2 on relevant nanometer and picosecond length- and time scales and with 100-mK temperature sensitivity. We discern excitonic contributions to the signal from heat by combining observations close to and far from exciton resonances, characterizing the photoinduced dynamics for each. Our approach is general and can be applied to any electronic material, including thermoelectrics, where heat and electronic observables spatially interplay, and it will enable direct and quantitative discernment of different types of coexisting energy without recourse to complex models or underlying assumptions.
Collapse
Affiliation(s)
- Hannah
L. Weaver
- Department
of Physics, University of California, Berkeley, California 94720, United States
| | - Cora M. Went
- Department
of Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Joeson Wong
- Department
of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, United States
| | - Dipti Jasrasaria
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Eran Rabani
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- The
Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Harry A. Atwater
- Department
of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, United States
| | - Naomi S. Ginsberg
- Department
of Physics, University of California, Berkeley, California 94720, United States
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Molecular
Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli
Energy NanoScience Institute, Berkeley, California 94720, United States
- STROBE
NSF Science & Technology Center, Berkeley, California 94720, United States
| |
Collapse
|
5
|
Yu Y, Li G, Xu Y, Hu C, Liu X, Cao L. Phase Diagram of High-Temperature Electron-Hole Quantum Droplet in Two-Dimensional Semiconductors. ACS NANO 2023; 17:15474-15481. [PMID: 37540772 DOI: 10.1021/acsnano.3c01365] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/06/2023]
Abstract
Quantum liquids, systems exhibiting effects of quantum mechanics and quantum statistics at macroscopic levels, represent one of the most exciting research frontiers of modern physical science and engineering. Notable examples include Bose-Einstein condensation (BEC), superconductivity, quantum entanglement, and a quantum liquid. However, quantum liquids are usually only stable at cryogenic temperatures, significantly limiting fundamental studies and device development. Here we demonstrate the formation of stable electron-hole liquid (EHL) with the quantum statistic nature at temperatures as high as 700 K in monolayer MoS2 and elucidate that the high-temperature EHL exists as droplets in sizes of around 100-160 nm. We also develop a thermodynamic model of high-temperature EHL and, based on the model, compile an exciton phase diagram, revealing that the ionized photocarrier drives the gas-liquid transition, which is subsequently validated with experimental results. The high-temperature EHL provides a model system to enable opportunities for studies in the pursuit of other high-temperature quantum liquids. The results can also allow for the development of quantum liquid devices with practical applications in quantum information processing, optoelectronics, and optical interconnections.
Collapse
Affiliation(s)
- Yiling Yu
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Guoqing Li
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Yan Xu
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Chong Hu
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Xiaoze Liu
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Linyou Cao
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
- Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, United States
- Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| |
Collapse
|
6
|
Sousa FB, Perea-Causin R, Hartmann S, Lafetá L, Rosa B, Brem S, Palekar C, Reitzenstein S, Hartschuh A, Malic E, Malard LM. Ultrafast hot electron-hole plasma photoluminescence in two-dimensional semiconductors. NANOSCALE 2023; 15:7154-7163. [PMID: 37009757 DOI: 10.1039/d2nr06732c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The transition metal dichalcogenide family of semiconducting two-dimensional materials has recently shown a prominent potential to be an ideal platform to study the exciton Mott transition into electron-hole plasma and liquid phases due to their strong Coulomb interactions. Here, we show that pulsed laser excitation at high pump fluences can induce this exciton Mott transition to an electron-hole plasma in mono and few-layer transition metal dichalcogenides at room temperature. The formation of an electron-hole plasma leads to a broadband light emission spanning from the near infrared to the visible region. In agreement with our theoretical calculations, the photoluminescence emission at high energies displays an exponential decay that directly reflects the electronic temperature - a characteristic fingerprint of unbound electron-hole pair recombination. Furthermore, two-pulse excitation correlation measurements were performed to study the dynamics of electronic cooling, which shows two decay time components, one of less than 100 fs and a slower component of few ps associated with the electron-phonon and phonon-lattice bath thermalizations, respectively. Our work may shed light on further studies of the exciton Mott transition into other two-dimensional materials and their heterostructures and its applications in nanolasers and other optoelectronic devices.
Collapse
Affiliation(s)
- Frederico B Sousa
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Raül Perea-Causin
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Sean Hartmann
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377 Munich, Germany
| | - Lucas Lafetá
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377 Munich, Germany
| | - Bárbara Rosa
- Institute of Solid State Physics, Technische Universität Berlin, 10623, Berlin, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universit ät Marburg, 35037 Marburg, Germany
| | - Chirag Palekar
- Institute of Solid State Physics, Technische Universität Berlin, 10623, Berlin, Germany
| | - Stephan Reitzenstein
- Institute of Solid State Physics, Technische Universität Berlin, 10623, Berlin, Germany
| | - Achim Hartschuh
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377 Munich, Germany
| | - Ermin Malic
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
- Department of Physics, Philipps-Universit ät Marburg, 35037 Marburg, Germany
| | - Leandro M Malard
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| |
Collapse
|
7
|
Liu M, Lian B, Lan Z, Sun H, Zhao Y, Sun T, Meng Z, Zhao C, Zhang J. Transcriptomic Profile Identifies Hippocampal Sgk1 as the Key Mediator of Ovarian Estrogenic Regulation on Spatial Learning and Memory and Aβ Accumulation. Neurochem Res 2022; 47:3369-3384. [PMID: 35915371 DOI: 10.1007/s11064-022-03690-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 06/14/2022] [Accepted: 07/12/2022] [Indexed: 11/28/2022]
Abstract
Previous studies have shown that ovarian estrogens are involved in the occurrence and pathology of Alzheimer's disease (AD) through regulation on hippocampal synaptic plasticity and spatial memory; however, the underlying mechanisms have not yet been elucidated at the genomic scale. In this study, we established the postmenopausal estrogen-deficient model by ovariectomy (OVX). Then, we used high-throughput Affymetrix Clariom transcriptomics and found 143 differentially expressed genes in the hippocampus of OVX mice with the absolute fold change ≥ 1.5 and P < 0.05. GO analysis showed that the highest enrichment was seen in long-term memory. Combined with the response to steroid hormone enrichment and GeneMANIA network prediction, the serum and glucocorticoid-regulated kinase 1 gene (Sgk1) was found to be the most potent candidate for ovarian estrogenic regulation. Sgk1 overexpression viral vectors (oSgk1) were then constructed and injected into the hippocampus of OVX mice. Morris water maze test revealed that the impaired spatial learning and memory induced by OVX was rescued by Sgk1 overexpression. Additionally, the altered expression of synaptic proteins and actin remodeling proteins and changes in CA1 spine density and synapse density induced by OVX were also significantly reversed by oSgk1. Moreover, the OVX-induced increase in Aβ-producing BACE1 and Aβ and the decrease in insulin degrading enzyme were significantly reversed by oSgk1. The above results show that multiple pathways and genes are involved in ovarian estrogenic regulation of the function of the hippocampus, among which Sgk1 may be a novel potent target against estrogen-sensitive hippocampal dysfunctions, such as Aβ-initiated AD.
Collapse
Affiliation(s)
- Mengying Liu
- The 305 Hospital of PLA, Beijing, 100017, China.,Department of Neurobiology, Army Medical University, Chongqing, 400038, China
| | - Biyao Lian
- Department of Pediatrics, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710004, China.,Department of Human Anatomy and Tissue Embryology, Ningxia Medical University, Yinchuan, 750004, China
| | - Zhen Lan
- Department of Neurobiology, Army Medical University, Chongqing, 400038, China
| | - Huan Sun
- Department of Neurobiology, Army Medical University, Chongqing, 400038, China.,Center for Brain Science, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, China
| | - Yangang Zhao
- Department of Neurology, Hainan Hospital of PLA General Hospital, Sanya, 572013, China
| | - Tao Sun
- Department of Neurobiology, Army Medical University, Chongqing, 400038, China
| | - Zhaoyou Meng
- Department of Neurobiology, Army Medical University, Chongqing, 400038, China
| | - Chengjun Zhao
- Department of Human Anatomy and Tissue Embryology, Ningxia Medical University, Yinchuan, 750004, China. .,Medical Sci-Tech Research Center, Ningxia Medical University, Yinchuan, 750004, China.
| | - Jiqiang Zhang
- Department of Neurobiology, Army Medical University, Chongqing, 400038, China.
| |
Collapse
|
8
|
Uddin SZ, Higashitarumizu N, Kim H, Yi J, Zhang X, Chrzan D, Javey A. Enhanced Neutral Exciton Diffusion in Monolayer WS 2 by Exciton-Exciton Annihilation. ACS NANO 2022; 16:8005-8011. [PMID: 35467828 DOI: 10.1021/acsnano.2c00956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Dominant recombination pathways in monolayer transition metal dichalcogenides (TMDCs) depend primarily on background carrier concentration, generation rate, and applied strain. Charged excitons formed in the presence of background carriers mainly recombine nonradiatively. Neutral excitons recombine completely radiatively at low generation rates, but experience nonradiative exciton-exciton annihilation (EEA) at high generation rates. Strain can suppress EEA, resulting in near-unity photoluminescence quantum yield (PL QY) at all exciton densities. Although exciton diffusion is the primary channel of energy transport in excitonic materials and a critical optoelectronic design consideration, the combined effects of these factors on exciton diffusion are not clearly understood. In this work, we decouple the diffusion of neutral and charged excitons with chemical counterdoping and explore the effect of strain and generation rate on exciton diffusion. According to the standard semiconductor paradigm, a shorter carrier recombination lifetime should lead to a smaller diffusion length. Surprisingly, we find that increasing generation rate shortens the exciton lifetime but increases the diffusion length in unstrained monolayers of TMDCs. When we suppress EEA by strain, both lifetime and diffusion length become independent of generation rate. During EEA one exciton nonradiatively recombines and kinetically energizes another exciton, which then diffuses fast. Our results probe concentration-dependent diffusion of pure neutral excitons by counterdoping and elucidate how strain controls exciton transport and many-body interactions in TMDC monolayers.
Collapse
Affiliation(s)
- Shiekh Zia Uddin
- Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Naoki Higashitarumizu
- Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Hyungjin Kim
- Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Jun Yi
- NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, United States
| | - Xiang Zhang
- NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, United States
- Faculties of Sciences and Engineering, The University of Hong Kong, Hong Kong, China
| | - Daryl Chrzan
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Materials Science and Engineering, University of California, Berkeley, Berkeley, California 94720, United States
| | - Ali Javey
- Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| |
Collapse
|