Exciton dynamics and annihilation in ws2 2d semiconductors pdf

The exciton lifetime when free of exciton annihilation was determined to be 806 37 ps, 401 25 ps, and 332 19 ps for ws2. However, its observation in quasi2d systems, such as semiconductor quantum wells, is rare. Pdf we systematically investigate the exciton dynamics in monolayer, bilayer, and trilayer ws2 twodimensional 2d crystals by timeresolved. Dissociation of twodimensional excitons in monolayer wse 2. A declining exciton annihilation rate is also witnessed. We systematically investigate the exciton dynamics in monolayered, bilayered, and trilayered ws2 twodimensional 2d crystals by timeresolved.

Exciton dynamics in monolayer transition metal dichalcogenides. Observation of rapid exciton exciton annihilation in. Exciton dynamics for the monolayer and fewlayer structures were found to be remarkably di. Bound exciton and free exciton states in gase thin slab. Mar 01, 2010 analysis of the kinetics obtained suggests that the observed acceleration of kinetic decay at low temperature originates from an increasing rate of exciton exciton annihilation. In this chapter, we will evaluate the optical response for 3d and 2d semiconductors. Exciton relaxation dynamics in a onedimensional semiconductor. Highly mobile chargetransfer excitons in twodimensional ws. Exciton dynamics in suspended monolayer and fewlayer mos 2 2d crystals. Apr 28, 2015 we systematically investigate the exciton dynamics in monolayered, bilayered, and trilayered ws2 twodimensional 2d crystals by timeresolved photoluminescence trpl spectroscopy. Ultrafast exciton dynamics in chemical heterogenous wse2. Tailored emission spectrum of 2d semiconductors using. Because the exciton density at the center of the spot is higher than at the edge, exciton exciton annihilation could lead to artificially broadening of we have carried out pump intensitydependent dynamics and transport measurements to rule out the interference from exciton exciton annihilation. At lower temperatures, we observed a more e cient excitonexciton interaction that suggests the contribution from.

Here r is the mirror reflectivity in our case r silver. Here, we have investigated the temperature t dependence of the transport dynamics of neutral excitons and charged excitons trions in atomically thin twodimensional crystals of the transitionmetal dichalcogenide ws2. This behavior follows from the ntype semiconducting nature of monolayer ws 2 on the sapphire substrate. Dynamics of exciton energy renormalization in monolayer. Physics of excitons and their transport in two dimensional. Jun xiao, mervin zhao, yuan wang and xiang zhang excitons. Exciton photon and phonon interactions in semiconductor quantum dots by kaijie xu excitons, photons, and phonons are elementary excitations that have been widely investigated in semiconductor systems. Jun xiao, mervin zhao, yuan wang and xiang zhang excitons in. Exciton relaxation cascade in twodimensional transition.

At high fluence, defects are filled and manybody interactions become important. In addition to the electronic band gaps, the exciton and trion binding energies, and the spinorbit splitting are. Jan 15, 2020 we investigate the carrier dynamics in monolayer ws 2 sio 2 and ws 2 gaas heterojunctions using timeresolved photoluminescence in this study. Longrange exciton transport and slow annihilation in two. Pdf lowtemperature photocarrier dynamics in monolayer. Monolayer transition metal dichalcogenides tmds are direct gap semiconductors with promising applications in diverse optoelectronic devices. Similar to other 2d systems, exciton exciton annihilation eea is then the dominant recombination path in a highdensity regime below the mott transition. When the supporting substrate is changed from sio2 to al2o3 or srtio3, the rate constant. Khounsarye and tengfei luo, thermal conductivity of organic bulk heterojunction solar cells. The band structure of mos2 strongly depends on the number of layers, and a transition from indirect to directgap semiconductor has been observed recently for a single layer of mos2. Temperature dependence of optical properties of monolayer.

To cite this article before page numbers are assigned, use the doi form of citation above. Following an introduction on the electronic structure of 2d npls, we discuss the dynamics of exciton dissociation by electron transfer to molecular acceptors. Perceptible excitontotrion conversion and signature of. At low excitation power, the trpl decays are nonexponential because of defectassisted recombination. Controlling valley splitting and polarization of dark and. Alloptical reversible manipulation of exciton and trion. Exciton dynamics and annihilation in ws2 2d semiconductors. Intrinsically dark and bright exciton energy is likely to play a key role in modulating the dynamics. Controlling exciton dynamics in twodimensional mos2 on. Highly mobile chargetransfer excitons in twodimensional. Zhi guo, doyun lee, joseph strzalka, haifeng gao,libai huang, ali m. Origin of the variation of exciton binding energy in semiconductors marc dvorak,1 suhuai wei,2 and zhigang wu1, 1department of physics, colorado school of mines, golden, colorado 80401, usa 2national renewable energy laboratory, golden, colorado 80401, usa received july 2012. Osa incoherent phonon population and excitonexciton.

Additionally, neutral exciton to charged exciton trion conversion is anticipated in the overall pl characteristics. Excitons in atomically thin 2d semiconductors and their. Suggested by the results, exciton transport in a semiconducting swcnt is di usional at room temperature, with high di usivity 350 cm2s and long di usion length. Femtosecond transient absorption spectroscopy and microscopy were employed to study exciton dynamics in suspended and si3n4 substratesupported monolayer and fewlayer mos2 2d crystals. Ultrafast dynamics of exciton formation in semiconductor. We systematically investigate the exciton dynamics in monolayered, bilayered, and trilayered ws2 twodimensional 2d crystals by timeresolved photoluminescence trpl spectroscopy. Atomically thin semiconductors, such as transition metal dichalcogenides. Controlling exciton dynamics in twodimensional mos 2 on hyperbolic metamaterialbased nanophotonic platform kwang 3jin 2,5lee1,5, wei xin, chunhao fann1, xinli ma3, fei xing4, jing liu, jihua zhang1, mohamed elkabbash1, chunlei guo1,2 1 institute of optics, university of rochester, rochester, new york, usa, 2 the guo chinaus photonics laboratory, changchun institute of optics, fine. Because the exciton density at the center of the spot is higher than at the edge, excitonexciton annihilation could lead to artificially broadening of we have carried out pump intensitydependent dynamics and transport measurements to rule out the interference from excitonexciton annihilation. Here, we investigated the carrier dynamics and manybody interactions in twodimensional 2d transition metal dichalcogenides tmds, using monolayer ws2. Effect of dielectric environment on excitonic dynamics in. Here, we show that the density threshold at which annihilation occurs can be tuned by changing the underlying substrate.

In order to directly probe exciton exciton scattering processes, femtosecond 2pe signal is measured as a function of excitation fluence and temperature. Bn, which decreases the exciton mean free path and thus the diffusion coefficient. Exciton dynamics in suspended monolayer and fewlayer mos2 2d. Joyce, james lloydhughes, qiang gao, hark hoe an, t. Atomically thin semiconductors such as monolayer mos2 and ws2 exhibit. Mos 2, transient absorption spectroscopy, exciton dynamics, exciton. Exciton dynamics, transport, and annihilation in atomically thin twodimensional semiconductors. Nonlinear photoluminescence in atomically thin layered wse2. This highly nonlinear behavior is attributed to diffusionassisted exciton exciton annihilation at a rate of 0. Ix is characterized by a larger binding energy, and its lifetime is orders of magnitude longer than that of the direct excitons, providing a significant platform for the manufacture of long. Carrier dynamics in monolayer ws2gaas heterostructures. Analysis of the kinetics obtained suggests that the observed acceleration of kinetic decay at low temperature originates from an increasing rate of exciton exciton annihilation. Additionally, valence states not explicitly participating in the exciton. Fast exciton annihilation by capture of electrons or holes.

Atomically thin layer transition metal dichalcogenides have been intensively investigated for their rich optical properties and potential applications on nanoelectronics. We have carried out excitation intensity dependent measurements that show negligible variations in dynamics with fluences ranging from 1. The longdistance exciton diffusion and subsequent efficient excitonexciton annihilation process determined the unusual multiexciton dynamics in atomically thin layered transition metal dichalcogenides. Fleming a a department of chemistry, university of california, berkeley, and physical biosciences division, lawrence berkeley national laboratory, berkeley, ca 94720, usa. Suppressing diffusionmediated exciton annihilation in 2d. Ultrafast charge transfer between mote2 and mos2 monolayers shudi pan, frank ceballos. The excitonexciton annihilation has also been observed in onedimensional structures, such as semiconducting carbon nanotubes 53,54. Transport dynamics of neutral excitons and trions in. Excitonexciton annihilation and biexciton stimulated. Intrinsically, dark and bright exciton energy splitting is likely to play a key role in modulating the dynamics. Osa observation of double indirect interlayer exciton in.

Supporting information exciton dynamics and annihilation. Singlettriplet annihilation limits exciton yield in poly. Incoherent phonon population and excitonexciton annihilation. Fundamental understandings on the dynamics of charge carriers and excitonic quasiparticles in semiconductors are of central importance for both manybody physics and promising optoelectronic and photonic applications. While excitons in these systems have been extensively researched, there currently lacks a consensus on mechanisms that control dynamics. Yuan l and huang l 2015 exciton dynamics and annihilation in ws2 2d semiconductors nanoscale 7 74028. The dynamics of an exciton persisted until the exciton underwent either. Nonlinear optical selection rule based on valleyexciton. In many cases, the surface chemistry of the qds determines the competition between auger relaxation and electronictovibrational energy transfer in. S4, indicating that exciton exciton annihilation processes. Huang, exciton dynamics and annihilation in ws2 2d semiconductors. Exciton annihilation and dephasing dynamics in semiconducting. Long yuan, libai huang we systematically investigate the exciton dynamics in monolayered, bilayered, and trilayered ws 2 twodimensional 2d crystals by timeresolved photoluminescence trpl spectroscopy. Here we investigated interlayer exciton dynamics and transport in ws2 wse2 heterobilayers in time, space and momentum domains using transient absorption microscopy combined with firstprinciples.

Long yuan and libai huang, exciton dynamics and annihilation in ws2 2d semiconductors, nanoscale, 7, 74027408 2015. Exciton dynamics for the monolayer and fewlayer structures were found to be remarkably different from those of thick crystals when probed at energies near that of the lowest energy direct exciton a exciton. At increasing excitation density, the exciton resonance energy exhibits a pronounced redshift followed by an anomalous blueshift. Bn is attributed to the additional phonon scattering mechanisms introduced by h.

Exciton annihilation an d dephasing dynamics in semiconducting singlewalled carbon nanotubes matthew w. Understanding the spatial motion of excitons is of both fundamental interest and central importance for optoelectrical applications. Singlelayer mos2 therefore becomes an efficient emitter of photoluminescence even at room temperature. Exciton dynamics play a critical role in the fundamental properties and functionalities of nanomaterials of interest for a variety of applications including optical detectors, solar energy conversion, lasers, and sensors. Strait, changjian zhang, weimin chan, christina manolatou, sandip tiwari, and farhan rana school of electrical and computer engineering, cornell university, ithaca, new york 14853, usa. In this perspective, we discuss extrinsic and intrinsic factors in exciton. Fast exciton annihilation by capture of electrons or holes by. Their combined citations are counted only for the first article. Upon excitation of the exciton transition, both stokes and antistokes. Excitons in 3d and 2d systems electrons and holes in an excited semiconductor create a quasiparticle, named exciton. Here, we report on scanning raman and on temperaturedependent, as well as timeresolved photoluminescence. While graphene has enabled the discovery of novel physics in electronic transport, the gapless nature of the crystal makes it less ideal for the study of optical phenomena.

The pl decay dynamics, while following biexponential trends, have revealed ample improvement in both the fast parameter 0. Large binding energy and unique exciton fine structure make the transition metal dichalcogenides tmdcs an ideal platform to study exciton behaviors in twodimensional 2d systems. Excitons in bulk and twodimensional semiconductors the wannier model derived in the previous chapter provides a simple framework for the inclusion of excitons in the optical properties of semiconductors. Pdf exciton dynamics, transport, and annihilation in. Roomtemperature excitonpolaritons with twodimensional ws2. Excitonexciton annihilation in twodimensional halide. However, its observation in quasi 2d systems, such as semiconductor quantum wells, is rare. Valleypolarized exciton dynamics in a 2d semiconductor heterostructure. Exciton annihilation in the two photosystems in chloroplasts at 100 degrees k. The findings provide useful information for designing and understanding the effect of h. Dissociation of twodimensional excitons in monolayer. In this work, we study the incoherent phonon and exciton population dynamics in monolayer ws2 by timeresolved resonance raman scattering spectroscopy.

Highly mobile chargetransfer excitons in twodimensional ws2. This thesis focuses on the exciton energy transfer between quantum dots, which is a physical process that involves all these elementary excitations. Pang j r, toh m, zhang x, kloc c, tan p h and eda g 20 lattice dynamics in monoand fewlayer sheets of ws2 and wse2 nanoscale 5 967783. Evidence for line width and carrier screening effects on excitonic. Van loosdrecht2,5 1state key laboratory of quantum. Exciton broadening in ws2 graphene heterostructures. Fast exciton annihilation by capture of electrons or holes by defects via auger scattering in monolayer metal dichalcogenides haining wang, jared h. Origin of the variation of exciton binding energy in. Singlettriplet annihilation limits exciton yield in poly3. Beyond the fundamental interest in this manybody process, exciton. At lower temperatures, we observed a more e cient exciton exciton interaction that suggests the contribution from. Lennardjoneslike potential of 2d excitons in monolayer ws2. After separation of centre of gravity and relative orbital motion a series of bound exciton states n1,2,3.

Twistangledependent interlayer exciton diffusion in ws2. Atomically thin semiconductors such as monolayer mos2 and ws2 exhibit nonlinear exciton exciton annihilation at notably low excitation densities below 10 excitonsum2 in mos2. A better understanding of exciton dynamics in nanomaterials is thus important both fundamentally and technologically. Exciton dynamics in semiconductor nanocrystals wheeler. Huang, exciton dynamics and annihilation in ws2 2d semiconductors, nanoscale 716, 74027408 2015. The role of ligands in determining the exciton relaxation. Temperature dependence of optical properties of monolayer ws2. Ultrafast dynamics of exciton formation in semiconductor nanowires chaw keong yong, hannah j. The large variation in reported annihilation rates and exciton lifetimes for a given excitation density might be attributed to a strong influence from the substrate. In this perspective, we discuss extrinsic and intrinsic factors in exciton dynamics, transport, and annihilation in 2d tmdcs. The efficient exciton exciton annihilation in 1l ws 2 implies that the inverse process, that is, multiple exciton generation could also be effective. We compare exciton transport and annihilation properties of 2d perovskites to those of tmdcs. The exciton lifetime when free of exciton annihilation was determined to be 806 37 ps, 401 25 ps, and 332 19 ps for ws2 monolayer, bilayer, and trilayer. Atomically thin semiconductors such as monolayer mos2 and ws2 exhibit nonlinear.

Osa giant photoluminescence enhancement in monolayer ws2 by. Imaging spin dynamics in monolayer ws2 by timeresolved kerr rotation microscopy elizabeth j mccormick, michael j newburger, yunqiu kelly luo et al. Supporting information exciton dynamics and annihilation in. The exciton lifetime and radiative lifetime for ws 2 gaas sample were determined to be 497 ps and 46 ns, respectively, which are much larger than those of the ws 2 sio 2 sample. However, an alloptical approach with the reversible feature is still a challenge. Optical properties of 2d semiconductor ws 2 chunxiao cong, jingzhi shang, yanlong wang, and ting yu. Exciton dynamics, transport, and annihilation in atomically thin twodimensional semiconductors l yuan, t wang, t zhu, m zhou, l huang the journal of physical chemistry letters 8 14, 337379, 2017. Thus, the localization and overlap ofelectron and hole states iscritical because of the 1r nature of the interaction.

Exciton dissociation dynamics and lightdriven h 2 generation. Pdf exciton dynamics and annihilation in ws2 2d semiconductors. Apr 24, 2018 twodimensional 2d semiconducting materials are promising building blocks for optoelectronic applications, many of which require efficient dissociation of excitons into free electrons and holes. We used afm to identify film thickness by putting scratches into the surface. In this chapter, we report a rare atomlike interaction between excitons in monolayer ws 2, measured using ultrafast absorption spectroscopy. Exciton dynamics, transport, and annihilation in atomically thin 2d semiconductors article pdf available in journal of physical chemistry letters 814 june 2017 with 590 reads.