Generalized Scaling Law for Exciton Binding Energy in Two-Dimensional Materials

Ahmad, Shahzad; Zubair, Muhammad; Jalil, Osama; Mehmood, Muhammad Qasim; Younis, Usman; Liu, X.; Ang, Kah Wee; Ang, L. K.

doi:10.1103/physrevapplied.13.064062

Cited by 19 publications

(21 citation statements)

References 71 publications

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“…The nonequilibrium free carriers generated by light excitation are confined within an ultrathin plane, giving rise to the substantial overlap of the wave functions of electrons and holes. For this reason, compared to their bulk counterparts, the exciton binding energy of 2DLMs is relatively high, − and the recombination of photogenerated electron–hole pairs is markedly expedited. As a result, the lifetime of photocarriers is considerably limited.…”

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confidence: 99%

Dielectric Contrast Tailoring for Polarized Photosensitivity toward Multiplexing Optical Communications and Dynamic Encrypt Technology

et al. 2022

ACS Nano

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A selective-area oxidation strategy is developed to polarize high-symmetry 2D layered materials (2DLMs). The dichroic ratio of the derived O-WS2/WS2 photodetector reaches ∼8, which is competitive among state-of-the-art polarization photodetectors. Finite-different time-domain simulations consolidate that the polarization-sensitive photoresponse is associated with anisotropic spacial confinement, which gives rise to distinct dielectric contrasts for linearly polarized light of various directions and thus the polarization-dependent near-field distribution. Furthermore, selective-area oxidation treatment brings about dual effects, comprising the in situ formation of seamless in-plane WS2 homojunctions by thickness tailoring and the formation of out-of-plane O-WS2/WS2 heterojunctions. As a consequence, the recombination of photocarriers is markedly suppressed, resulting in outstanding photosensitivity with the optimized responsivity, external quantum efficiency, and detectivity of 0.161 A/W, 49.4%, and 1.4 × 1011 Jones for an O-WS2/WS2 photodetector in a self-powered mode. A scheme of multiplexing optical communications is revealed by harnessing the intensity and polarization state of light as independent transmission channels. Furthermore, dynamic encryption by leveraging the polarization state as a secret key is proposed. In the end, broad universality is reinforced through the induction of linear dichroism within 2D WSe2 crystals. On the whole, this study provides an additional perspective on polarization optoelectronics based on 2DLMs.

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confidence: 99%

Dielectric Contrast Tailoring for Polarized Photosensitivity toward Multiplexing Optical Communications and Dynamic Encrypt Technology

et al. 2022

ACS Nano

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“…On the other hand, the binding energy of the A 1s exciton reduces in the case of a multi-layer MoS 2 due to increased screening. 33,36 Such reduction in the binding energy can weaken the exciton transition strength 18 in multi-layer MoS 2 relative to 1L-MoS 2 , lowering the efficiency of the energy transfer process. However, the increased radiative lifetime of carriers in a multi-layer MoS 2 37,38 can aid efficient collection of photocarriers generated through the NRET, enhancing the quantum efficiency of photodetection (Figure 2a,b).…”

Section: Resultsmentioning

confidence: 99%

“…While the overall band structure is dependent on the number of layers, the direct band gap at the “K” point is a very weak function of thickness, as predicted both theoretically and observed experimentally. − Hence, the spectral resonance that exists between SnSe 2 and monolayer MoS 2 as discussed earlier is also applicable in the case of a multi-layer MoS 2 . On the other hand, the binding energy of the A 1s exciton reduces in the case of a multi-layer MoS 2 due to increased screening. , Such reduction in the binding energy can weaken the exciton transition strength in multi-layer MoS 2 relative to 1L-MoS 2 , lowering the efficiency of the energy transfer process. However, the increased radiative lifetime of carriers in a multi-layer MoS 2 , can aid efficient collection of photocarriers generated through the NRET, enhancing the quantum efficiency of photodetection (Figure a,b).…”

Section: Results and Discussionmentioning

confidence: 99%

Negative Differential Photoconductance as a Signature of Nonradiative Energy Transfer in van der Waals Heterojunction

2021

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The physical proximity of layered materials in their van der Waals heterostructures (vdWhs) aids interfacial phenomena such as charge transfer (CT) and energy transfer (ET). Besides providing fundamental insights, CT and ET also offer routes to engineer optoelectronic properties of vdWhs. For example, harnessing ET in vdWhs can help to overcome the limitations of optical absorption imposed by the ultra-thin nature of layered materials and thus provide an opportunity for in situ enhancement of quantum efficiency for light-harvesting and sensing applications. While several spectroscopic studies on vdWhs probed the dynamics of CT and ET, the possible contribution of ET in the photocurrent generation remains largely unexplored. In this work, we investigate the role of nonradiative energy transfer (NRET) in the photocurrent through a vertical vdWh of SnSe2/MoS2/TaSe2. We observe an unusual negative differential photoconductance (NDPC) arising from the existence of NRET across the SnSe2/MoS2 junction. Modulation of the NRET-driven NDPC characteristics with optical power results in a striking transition of the photocurrent’s power law from a sublinear to a superlinear regime. Our observations reveal the nontrivial influence of ET on the photoresponse of vdWhs, which offer insights to harness ET in synergy with CT for vdWh based next-generation optoelectronics.

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“…The idea of fractional-dimensional space has lately been used to effectively examine physical phenomena in complex objects that are anisotropic and nonhomogeneous in character. Using this approach of fractionaldimensional space, various electromagnetic problems have been solved such as the study of Bessel beams in space-fractional dimension [4], achieving precise values of binding-energies for optical materials [5], and charge transport in chaotic media [6,7]. This helps to understand the underlying physical phenomenon in terms of dimensionality.…”

Section: Introductionmentioning

confidence: 99%

Modeling of optical wave propagation through turbulent atmosphere using fractional approach for FSO wireless communication

2023

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Free space optical (FSO) wireless communication has emerged as a viable alternative to the existing fiber optics and radio frequency (RF) communications due to its ability to operate in unlicensed spectrum, offering huge data handling capacities and being cost effective with easy deployment. The underlying communication mechanism in the FSO link is based upon the laser beam propagation model. The propagating free space optical beam undergoes signal degradation due to refraction and diffraction caused by atmospheric turbulence measured by refractive index structure parameter (Cn 2). In this work, a novel, robust analytical model for propagating Gaussian-beam through atmospheric turbulence is presented, by solving the space-fractional paraxial wave equation. We report analytical expressions for the intensity and long-term beam spreading of a Gaussian beam in terms of space-fractional parameter D, for the range 2<D≤3. This range of parameter D, defines the effective number of euclidean space corresponding to atmospheric turbulence levels faced by the propagating Gaussian beam in the FSO link. The results of the proposed fractional model and the existing models agreed well, therefore the D-dimensional parameter can be used to effectively express the value of refractive index structure parameter (Cn 2). The classical values of Cn 2 ranges form 10-13 to 10-16 for strong to weak fluctuations respectively. However, in fractional-dimension scale, these fluctuations can be express as D = 2.668 (strong fluctuations) to D = 2.999 (weak fluctuations). The ideal case of free space beam propagation can be expressed as D = 3, with no turbulence. Moreover, we have studied the fractional-dimension model performance for varying wavelengths. Further, based upon a practical example, we proposed a self-sustainable FSO link architecture to efficiently minimize the effect of weak and strong fluctuations on the propagating optical beam, based upon the D-dimension fractional parameter, hence ensuring reliability of FSO link.

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Generalized Scaling Law for Exciton Binding Energy in Two-Dimensional Materials

Cited by 19 publications

References 71 publications

Dielectric Contrast Tailoring for Polarized Photosensitivity toward Multiplexing Optical Communications and Dynamic Encrypt Technology

Dielectric Contrast Tailoring for Polarized Photosensitivity toward Multiplexing Optical Communications and Dynamic Encrypt Technology

Negative Differential Photoconductance as a Signature of Nonradiative Energy Transfer in van der Waals Heterojunction

Modeling of optical wave propagation through turbulent atmosphere using fractional approach for FSO wireless communication

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