Ultrafast Drift Current Terahertz Emission Amplification in the Monolayer WSe<sub>2</sub>/Si Heterostructure

Song, Fanchen; Zu, Xinzhi; Zhang, Zeyu; Jia, Tingyuan; Wang, Chunwei; Huang, Sihao; Liu, Zhengzheng; Xuan, Hongwen; Du, Juan

doi:10.1021/acs.jpclett.2c03347

Cited by 4 publications

(9 citation statements)

References 34 publications

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“…The out-of-plane photocurrent emission process could be ascribed to a longitudinal gradient diffusion of the carriers that drifted by the built-in electric field at the surface. 27 The magnitude of the drift current could be mainly related to the number of excited carriers, which reflects the optical transition probability. In contrast, as mentioned above, the direction and intensity of the shift current could be related to the crystal symmetry and the band occupation of the excited state.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…28,33,38 The other coefficients parametrize the helicity-independent photocurrents that depend on the linear polarization of light (L 1 and L 2 ), and the polarization-independent component photocurrent D represents the drift current. 13,39 Here, C, L 1 , and L 2 are the coefficients for the CPGE, linear photogalvanic effect, and linear photon drag effect current, respectively. 39 It is worth noting that petal morphology differs while excited with tunable photon energy from 650 to 500 nm, as shown in Figure S4.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The amplitude oscillates periodicity with 4-fold symmetry, which reveals a sinusoidal dependence with the polarization of the incident light. The circular polarization dependence for the photocurrent could be quantified using a phenomenological expression by − J ∝ C nobreak0em0.1em⁡ sin ( 2 θ ) + L 1 nobreak0em0.1em⁡ sin ( 4 θ ) + L 2 nobreak0em0.1em⁡ cos ( 4 θ ) + D where J is the photogenerated current, which is proportional to the measured emission terahertz peak, θ is the QWP angle, and parameter C phenomenologically represents the magnitude and direction difference of the photocurrent pumped by left- and right-hand circularly polarized photons. ,, The other coefficients parametrize the helicity-independent photocurrents that depend on the linear polarization of light ( L 1 and L 2 ), and the polarization-independent component photocurrent D represents the drift current. , Here, C , L 1 , and L 2 are the coefficients for the CPGE, linear photogalvanic effect, and linear photon drag effect current, respectively . It is worth noting that petal morphology differs while excited with tunable photon energy from 650 to 500 nm, as shown in Figure S4.…”

Section: Resultsmentioning

confidence: 99%

“…12 The terahertz radiation could reflect the transportation dynamics of the photocurrents in two kinds: the shift current and the drift current. 13 The shift currents represent the carrier displacement in different spatial positions and the drift currents are typically associated with the carriers accelerating by the energy band alignments at the interface. Besides, the shift currents could probe the valley polarizations by transient probing the carrier transportation in the excited states pumped by circularly polarized photons.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Especially, terahertz radiation could be detected when the transient photocurrent vanished in the picosecond time scale . The terahertz radiation could reflect the transportation dynamics of the photocurrents in two kinds: the shift current and the drift current . The shift currents represent the carrier displacement in different spatial positions and the drift currents are typically associated with the carriers accelerating by the energy band alignments at the interface .…”

Section: Introductionmentioning

confidence: 99%

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Intrinsic Switchable Valley-Polarized Photocurrent in ε-InSe

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et al. 2024

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Valleytronics, focusing on the charge carriers occupying valleys (local energy extrema) of the energy bands in semiconductors, demonstrates an additional degree of freedom besides the spin and charge. Usually, the inequivalent valley "states" in transition metal disulfides (TMDs) could be manipulated by external magnetic fields by controlling the valley-polarized carriers in spin-coupled valleys. Here, we found that the valley polarization of the photocurrent in ε-InSe could be intrinsically manipulated without the external field by the all-optical contactless method. The transient circular photogalvanic effect (CPGE)-induced photocurrent revealed by terahertz emission could be reversed only by selected pumping carriers from vertically split valence bands into different Rashba valleys. The switchable Rashba valley polarization, i.e., the optical orienting valley degree of freedom, could be fulfilled by the synergetic effects between the momentum-dependent Zeeman-like field due to the emergent nonzero Berry curvature and the Rashba splitting. Our results suggest that the spontaneous symmetry breaking could degenerate the given valley in ε-InSe and give a new roadmap for the manipulation of the valley degree of freedom intrinsically.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Intrinsic Switchable Valley-Polarized Photocurrent in ε-InSe

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ACS Photonics

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Emerging probing perspective of two-dimensional materials physics: terahertz emission spectroscopy

Wu,

Wang,

Bao

et al. 2024

Light Sci Appl

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Terahertz (THz) emission spectroscopy (TES) has emerged as a highly effective and versatile technique for investigating the photoelectric properties of diverse materials and nonlinear physical processes in the past few decades. Concurrently, research on two-dimensional (2D) materials has experienced substantial growth due to their atomically thin structures, exceptional mechanical and optoelectronic properties, and the potential for applications in flexible electronics, sensing, and nanoelectronics. Specifically, these materials offer advantages such as tunable bandgap, high carrier mobility, wideband optical absorption, and relatively short carrier lifetime. By applying TES to investigate the 2D materials, their interfaces and heterostructures, rich information about the interplay among photons, charges, phonons and spins can be unfolded, which provides fundamental understanding for future applications. Thus it is timely to review the nonlinear processes underlying THz emission in 2D materials including optical rectification, photon-drag, high-order harmonic generation and spin-to-charge conversion, showcasing the rich diversity of the TES employed to unravel the complex nature of these materials. Typical applications based on THz emissions, such as THz lasers, ultrafast imaging and biosensors, are also discussed. Step further, we analyzed the unique advantages of spintronic terahertz emitters and the future technological advancements in the development of new THz generation mechanisms leading to advanced THz sources characterized by wide bandwidth, high power and integration, suitable for industrial and commercial applications. The continuous advancement and integration of TES with the study of 2D materials and heterostructures promise to revolutionize research in different areas, including basic materials physics, novel optoelectronic devices, and chips for post-Moore’s era.

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Sensitive Characterization of the Graphene Transferred onto Varied Si Wafer Surfaces via Terahertz Emission Spectroscopy and Microscopy (TES/LTEM)

Yang,

Laarman,

Tonouchi

2024

Materials

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Graphene shows great potential in developing the next generation of electronic devices. However, the real implementation of graphene-based electronic devices needs to be compatible with existing silicon-based nanofabrication processes. Characterizing the properties of the graphene/silicon interface rapidly and non-invasively is crucial for this endeavor. In this study, we employ terahertz emission spectroscopy and microscopy (TES/LTEM) to evaluate large-scale chemical vapor deposition (CVD) monolayer graphene transferred onto silicon wafers, aiming to assess the dynamic electronic properties of graphene and perform large-scale graphene mapping. By comparing THz emission properties from monolayer graphene on different types of silicon substrates, including those treated with buffered oxide etches, we discern the influence of native oxide layers and surface dipoles on graphene. Finally, the mechanism of THz emission from the graphene/silicon heterojunction is discussed, and the large-scale mapping of monolayer graphene on silicon is achieved successfully. These results demonstrate the efficacy of TES/LTEM for graphene characterization in the modern graphene-based semiconductor industry.

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Ultrafast Drift Current Terahertz Emission Amplification in the Monolayer WSe₂/Si Heterostructure

Cited by 4 publications

References 34 publications

Intrinsic Switchable Valley-Polarized Photocurrent in ε-InSe

Intrinsic Switchable Valley-Polarized Photocurrent in ε-InSe

Emerging probing perspective of two-dimensional materials physics: terahertz emission spectroscopy

Sensitive Characterization of the Graphene Transferred onto Varied Si Wafer Surfaces via Terahertz Emission Spectroscopy and Microscopy (TES/LTEM)

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Ultrafast Drift Current Terahertz Emission Amplification in the Monolayer WSe2/Si Heterostructure

Cited by 4 publications

References 34 publications

Intrinsic Switchable Valley-Polarized Photocurrent in ε-InSe

Intrinsic Switchable Valley-Polarized Photocurrent in ε-InSe

Emerging probing perspective of two-dimensional materials physics: terahertz emission spectroscopy

Sensitive Characterization of the Graphene Transferred onto Varied Si Wafer Surfaces via Terahertz Emission Spectroscopy and Microscopy (TES/LTEM)

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Ultrafast Drift Current Terahertz Emission Amplification in the Monolayer WSe₂/Si Heterostructure