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507 results on '"Liu, Yushen"'

34. Pure spin current generation with photogalvanic effects in h-BN/graphene/h-BN van der Waals vertical heterostructures.

Author

Tao, Xixi, Jiang, Peng, Dong, Yaojun, Zhou, Jinhua, Yang, Xifeng, Zheng, Xiaohong, and Liu, Yushen

Abstract

We have computationally demonstrated a new method for generating pure spin current with the photogalvanic effect (PGE) by constructing transport junctions using h-BN/graphene/h-BN van der Waals (vdW) heterostructure leads. It has been observed that the pure spin current without any accompanying charge current induced by the PGE can consistently be obtained, regardless of photon energy and polarization/helicity angle, as well as the specific type of polarization (linear, circular, or elliptical). The mechanism lies in the structural inversion symmetry and real space spin polarization antisymmetry of the junctions. We also found that pure spin current can be generated whether we decrease or increase the interlayer distance by applying compressive or tensile strain to the h-BN/graphene/h-BN vdW vertical heterostructure leads. Additionally, by increasing the h-BN sheets on both sides of the graphene nanoribbons for the two leads, we observed large spin splitting and were able to generate a pure spin current. These findings provide a new approach for achieving pure spin current in graphene nanoribbons and highlight the significance of vdW heterostructures in designing spintronic devices. [ABSTRACT FROM AUTHOR]

Published
2024
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35. CsPbBr3 perovskite quantum dots/p-GaN heterojunction for ultraviolet-visible spectrum photodetectors.

Author

Liu, Yushen, Ye, Bingjie, Gao, Yang, Yang, Xifeng, Peng, Mingfa, and Yang, Guofeng

Subjects
*PHOTOELECTRIC devices, *SPECTRAL sensitivity, *HETEROJUNCTIONS, *ENERGY bands, *LIGHT absorption, *QUANTUM dots, *PHOTOELECTRICITY
Abstract

All-inorganic perovskites have attracted increasing attention because of their strong environmental stability and excellent photoelectric properties. However, the limited spectral response range of perovskite photodetectors restricts them in practical applications. In this work, an ultraviolet–visible photodetector with a wide spectral response and a high responsivity was prepared by constructing a CsPbBr3 quantum dots (QDs)/p-GaN heterojunction. The type-II energy band alignment formed by the heterojunction is conducive to the transport of photogenerated carriers, resulting in a high responsivity. Under certain conditions, the device can obtain responsivity values of 5 A/W and 850 mA/W under 350 and 725 nm illumination, respectively, which are comparable to those of other perovskite-based photodetectors. In addition, the photoresponse mechanism of the device is revealed through first-principles calculations of the heterojunction and the device. The enhanced light absorption of the heterojunction and the special band bending under different bias voltages improve the photoelectric performance of the device. This work can provide valuable insights into high-performance photodetectors based on all-inorganic perovskite QDs heterojunctions in terms of band regulation and device performance improvement. [ABSTRACT FROM AUTHOR]

Published
2024
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44. Thermoelectric Design of Delta-Doped β-(AlxGa1–x)₂O₃/Ga₂O₃ Metal Insulator Semiconductor High-Electron Mobility Transistors

Author

Shao, Zhenguang, Shao, Mengting, Qiao, Guang, Hong, Xuekun, Yu, Hailin, Yang, Xifeng, You, Haifan, Chen, Dunjun, Liu, Changjiang, and Liu, Yushen

Abstract

This work presents thermoelectric (TE) devices design of delta-doped $\beta $ -(AlxGa $_{{1}-{x}}$ )2O3/Ga2O3 metal insulator semiconductor high electron mobility transistors (MIS-HEMTs) using TCAD simulations. The TE properties of devices were comprehensively investigated with various temperature, gate voltages, gate lengths, delta-doping concentrations, and positions. With high delta-doping concentrations, a parasitic current channel is induced and that reduces electron chemical potential, resulting in high conductivity, a low Seebeck coefficient, and a reduced turn on voltage. Moving delta-doping positions closer to the $\beta $ -(AlxGa $_{{1}-{x}}$ )2O3/Ga2O3 interface enhances the concentration of the 2-D electron gas (2DEG), which screens the strong polar optical-phonon scattering and improves 2DEG mobility. For delta-doping positions at 1 nm, the power factor is improved due to quantum effect and energy filter effect, allowing the trade-off relationship between $\sigma $ and S to be mitigated. Expanding gate lengths increases channel electron temperature at gate edge near drain side. These results provide valuable insights and crucial guidance for the design of high-performance $\beta $ -(AlxGa $_{{1}-{x}}$ )2O3/Ga2O3 MIS-HEMTs for TE and temperature sensing applications.

Published
2024
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47. Lead‐Free Perovskites with Photochromism and Reversed Thermochromism for Repeatable Information Writing and Erasing.

Author

Sheng, Yuhang, Gui, Qingfeng, Zhang, Yi, Yang, Xingru, Xing, Fangjian, Liu, Cihui, Di, Yunsong, Wei, Shibiao, Cao, Guiyuan, Yang, Xifeng, Zhang, Xiaowei, Liu, Yushen, and Gan, Zhixing

Subjects
THERMOCHROMISM, PEROVSKITE, WRITING processes, EXCITON theory, SONICATION, PHOTOCHROMISM
Abstract

Recently, novel optical information writing strategies have been developed based on fluorescent change of halide perovskites generated by light induced structural transformation. However, to date, the repeatable writing and erasing of fluorescent patterns are still a major challenge. Herein, lead‐free Cs3InCl6:Sb3+ perovskite with photochromism and reversed thermochromism is developed for repeatable information writing and erasing. The original Cs3InCl6:Sb3+ perovskite synthesized by a modified hot‐injection method exhibits green photoluminescence (PL), which is caused by recombination of self‐trapped excitons. After treating with ultrasonication and heating, the green PL gradually turns to blue emission, which is related to surficial Cl vacancies that are generated or exposed due to the desorption of surfactants. Under continuous UV light irradiation, due to the photo repairing effect, the blue emission gradually vanishes, the fluorescent color recovers to green. Based on this photochromic effect, fluorescent patterns are drawn by UV exposure with mask. Moreover, the green PL color can again return to blue by heating at 100 °C. Thus, the photochromism‐induced fluorescent patterns can be simply erased based on the reversed thermochromism effect. Therefore, repeatable optical information writing and thermal erasure are demonstrated based on reversible PL change of Cs3InCl6:Sb3+. [ABSTRACT FROM AUTHOR]

Published
2024
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