Electron transfer across heterostructure interfaces plays a pivotal role in the functionality of modern electronic and optoelectronic devices, such as photocatalysts, solar cells, and phototransistors. However, interaction with ultrafast lasers could trigger a nonlinear optical response within individual materials to compete with the interfacial photocurrent in the heterostructure. Distinguishing the interplay between interfacial photocurrent and surface nonlinear photocurrent is challenging yet interesting. Herein, terahertz (THz) emission spectroscopy is employed to demonstrate the synergistic interaction between interfacial charge transfer and nonlinear photocurrent (photogalvanic effect in MoS2 and photon drag effect in graphene), thereby enhancing THz radiation in the graphene/MoS2 heterostructure compared with pure MoS2 and graphene. Interestingly, the contribution of interlayer charge transfer to the THz radiation gradually increases as the pump fluence increasing from 0.14 mJ/cm2 to 1.70 mJ/cm2. Our work offers an effective way to actively control the interface effect of heterostructures, potentially leading to advances in the utilization of graphene-based heterostructures in photonics and electronics devices.
We report the optical response of layered bulk and monolayer SnS2 at the surface. The physical mechanism for terahertz (THz) emission in bulk and monolayer SnS2 has been proposed. At 40° incident angle, the drift current accompanied by the surface nonlinear polarization concurrently contribute to THz surface emission in bulk SnS2. The THz radiation in monolayer SnS2 is mainly attributed to the drift photocurrent, which is insensitive to the crystalline symmetry and the pump polarization direction. The corresponding investigation could not only help to clarify the relationship of layer-dependent optical properties, but also make a significant contribution in understanding the nonlinear physical process in other transition metal dichalcogenides (TMDs) materials.
Two-dimensional/ three-dimensional (2D/3D) van der Waals (vdW) heterostructures are one of the most potential candidates for table-top pulse terahertz (THz) emitters. Hence, manipulating carrier information at the interface is important to optimize THz emission performance. Photoinduced doping is an effective way to embellish the carrier characteristic at the interface. Here, we applied the photoinduced doping effect to dynamically manipulate the THz generation process from graphene-silicon (Gr-Si) heterostructure. When photoinduced doping is applied by using 532 nm continuous wave (CW) laser, THz radiation decreases with the increase of CW pump power at the reverse bias. The photoinduced doping attenuates the interfacial built-in electric field, resulting in the decrease of transient photocurrent and further reduction of THz radiation. This photogenerated carrier screening effect has achieved a 95.4% intrinsic THz modulation depth (MD) at the external excitation of 200 mW CW laser under reverse bias voltage -30 V. The intrinsic THz MD is much higher than previous report value due to the optimized heterostructure fabrication and the optimized light spot overlap of CW laser and femtosecond laser. This work proposes a non-destructive and reversible method to actively manipulate the THz emission at the vdW interface and provides an optimized route to realize high intrinsic THz MD in THz region.
Conference Committee Involvement (4)
Infrared, Millimeter-Wave, and Terahertz Technologies XI
13 October 2024 | Nantong, Jiangsu, China
Infrared, Millimeter-Wave, and Terahertz Technologies X
15 October 2023 | Beijing, China
Infrared, Millimeter-Wave, and Terahertz Technologies IX
5 December 2022 | Online Only, China
Infrared, Millimeter-Wave, and Terahertz Technologies VIII
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