Junku Liu

China Academy of Space Technology

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Lin Xiao

Sichuan Research Center of New Materials

Qunqing Li

Xiamen University

Shoushan Fan

Tsinghua University

Kaili Jiang

Tsinghua University

Nan Guo

Northeast Agricultural University

Yuanhao Jin

Collaborative Innovation Center of Quantum Matter

Yi Jia

Qingdao University

Yuan Zou

Sichuan University

Guanhong Li

National Sun Yat-sen University

Qingkai Qian

Chongqing University

Cooperative Institutions

Tsinghua University

Peking University

Chinese Academy of Sciences

Collaborative Innovation Center of Quantum Matter

China Academy of Space Technology

Foxconn (China)

University of Chinese Academy of Sciences

Zhejiang University

Nankai University

Beijing Academy of Quantum Information Sciences

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Efficient Dispersive Waves Generation From Argon-Filled Anti-Resonant Nodeless Fiber

Conference on Lasers and Electro-Optics (2017)

Fanchao Meng Shoufei Gao Yingying Wang Pu Wang Junku Liu

We report dispersive waves generation in an argon-filled anti-resonant nodeless fiber pumped by ultrashort pulses centered at different wavelengths. The conversion efficiency can be as high as 16% with a bandwidth below 10 nm.

Frequency Conversion

10.1364/cleo_si.2017.stu3k.4

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Citations (3)

Photovoltaic Effect and Evidence of Carrier Multiplication in Graphene Vertical Homojunctions with Asymmetrical Metal Contacts

ACS Nano (2015)

Jingjing Chen Qinsheng Wang J. Meng Xiaoxing Ke Gustaaf Van Tendeloo

Graphene exhibits exciting potentials for high-speed wideband photodetection and high quantum efficiency solar energy harvest because of its broad spectral absorption, fast photoelectric response, and potential carrier multiplication. Although photocurrent can be generated near a metal-graphene interface in lateral devices, the photoactive area is usually limited to a tiny one-dimensional line-like interface region. Here, we report photoelectric devices based on vertical graphene two-dimensional homojunction, which is fabricated via vertically stacking four graphene monolayers with asymmetric metal contacts. The devices show excellent photovoltaic output with excitation wavelength ranging from visible light to mid-infrared. The wavelength dependence of the internal quantum efficiency gives direct evidence of the carrier multiplication effect in graphene. The simple fabrication process, easy scale-up, large photoresponsive active area, and broadband response of the vertical graphene device are very promising for practical applications in optoelectronics and photovoltaics.

Photodetection

Photocurrent

Quantum Efficiency

Multiple exciton generation

10.1021/acsnano.5b02356

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Citations (25)

Fast Adaptive Thermal Camouflage Based on Flexible VO₂/Graphene/CNT Thin Films

Nano Letters (2015)

Lin Xiao He Ma Junku Liu Wei Zhao Yi Jia

Adaptive camouflage in thermal imaging, a form of cloaking technology capable of blending naturally into the surrounding environment, has been a great challenge in the past decades. Emissivity engineering for thermal camouflage is regarded as a more promising way compared to merely temperature controlling that has to dissipate a large amount of excessive heat. However, practical devices with an active modulation of emissivity have yet to be well explored. In this letter we demonstrate an active cloaking device capable of efficient thermal radiance control, which consists of a vanadium dioxide (VO2) layer, with a negative differential thermal emissivity, coated on a graphene/carbon nanotube (CNT) thin film. A slight joule heating drastically changes the emissivity of the device, achieving rapid switchable thermal camouflage with a low power consumption and excellent reliability. It is believed that this device will find wide applications not only in artificial systems for infrared camouflage or cloaking but also in energy-saving smart windows and thermo-optical modulators.

Camouflage

Cloaking

Optical engineering

10.1021/acs.nanolett.5b04090

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Citations (293)

WSe<inf>2</inf>-In<inf>2</inf>O<inf>3</inf> nanowire infrared phototransistor

Nan Guo Junku Liu Yi Jia Sijia Wang Lei Wang

We report on a hybrid phototransistor that consists of In ₂ O ₃ nanowire covered with multilayer WSe ₂ . The absorption of infrared light in multilayer WSe ₂ forms the accumulation of photogenerated carriers at the interface between WSe ₂ and In ₂ O ₃ to enhance the conductance of nanowire. A responsivity of ~10 ⁴ A W ^-1 and an on/off ratio of ~10 ⁶ are obtained with 940 nm light irradiation at room temperature. The spectral response can be observed for photon energy near the bandgap of WSe ₂ .

10.1109/cleopr.2017.8118700

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Dielectric-Like Behavior of Graphene in Au Plasmon Resonator

Nanoscale Research Letters (2016)

Junku Liu Qunqing Li Mo Chen Mengxin Ren Lihui Zhang

Graphene has proven to be a promising conductive layer in fabricating optical plasmon resonators on insulator substrate using electron beam lithography and has the potential to construct electrically controlled active plasmon resonators. In this study, we investigate the effect of graphene on plasmon resonance using graphene and Au plasmon resonator system as a model at visible and near-infrared wavelength. Our experiment data show that the presence of graphene does not weaken and annihilate the plasmon resonance peaks, instead it predominantly makes the peaks redshift, which is similar to the behavior of depositing SiO2 film on Au plasmon resonators. This fact indicates that graphene predominantly exhibits dielectric-like behavior at visible and near-infrared wavelength, which can be attributed to the low carrier density in graphene compared with metals.

Localized surface plasmon

Nanochemistry

10.1186/s11671-016-1753-6

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Citations (1)

Hybrid WSe₂–In₂O₃ Phototransistor with Ultrahigh Detectivity by Efficient Suppression of Dark Currents

ACS Applied Materials & Interfaces (2017)

Nan Guo Fan Gong Junku Liu Yi Jia Shaofan Zhao

Photodetectors based on low-dimensional materials have attracted tremendous attention because of their high sensitivity and compatibility with conventional semiconductor technology. However, up until now, developing low-dimensional phototransistors with high responsivity and low dark currents over broad-band spectra still remains a great challenge because of the trade-offs in the potential architectures. In this work, we report a hybrid phototransistor consisting of a single In2O3 nanowire as the channel material and a multilayer WSe2 nanosheet as the decorating sensitizer for photodetection. Our devices show high responsivities of 7.5 × 105 and 3.5 × 104 A W-1 and ultrahigh detectivities of 4.17 × 1017 and 1.95 × 1016 jones at the wavelengths of 637 and 940 nm, respectively. The superior detectivity of the hybrid architecture arises from the extremely low dark currents and the enhanced photogating effect in the depletion regime by the unique design of energy band alignment of the channel and sensitizer materials. Moreover, the visible to near-infrared absorption properties of the multilayer WSe2 nanosheet favor a broad-band spectral response for the devices. Our results pave the way for developing ultrahigh-sensitivity photodetectors based on low-dimensional hybrid architectures.

Photodetection

Photodiode

Nanosheet

Specific detectivity

10.1021/acsami.7b10698

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Citations (50)

Electrical Contacts in Monolayer Arsenene Devices

ACS Applied Materials & Interfaces (2017)

Yangyang Wang Meng Ye Mouyi Weng Jingzhen Li Xiuying Zhang

Arsenene, arsenic analogue of graphene, as an emerging member of two-dimensional semiconductors (2DSCs), is quite promising in next-generation electronic and optoelectronic applications. The metal electrical contacts play a vital role in the charge transport and photoresponse processes of nanoscale 2DSC devices and even can mask the intrinsic properties of 2DSCs. Here, we present a first comprehensive study of the electrical contact properties of monolayer (ML) arsenene with different electrodes by using ab initio electronic calculations and quantum transport simulations. Schottky barrier is always formed with bulk metal contacts owing to the Fermi level pinning (pinning factor S = 0.33), with electron Schottky barrier height (SBH) of 0.12, 0.21, 0.25, 0.35, and 0.50 eV for Sc, Ti, Ag, Cu, and Au contacts and hole SBH of 0.75 and 0.78 eV for Pd and Pt contacts, respectively. However, by contact with 2D graphene, the Fermi level pinning effect can be reduced due to the suppression of metal-induced gap states. Remarkably, a barrier free hole injection is realized in ML arsenene device with graphene-Pt hybrid electrode, suggestive of a high device performance in such a ML arsenene device. Our study provides a theoretical foundation for the selection of favorable electrodes in future ML arsenene devices.

Electrical contacts

Contact resistance

10.1021/acsami.7b08513

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Citations (83)

Light‐Driven WSe₂‐ZnO Junction Field‐Effect Transistors for High‐Performance Photodetection

Advanced Science (2019)

Nan Guo Lin Xiao Fan Gong Man Luo Fang Wang

Abstract Assembling nanomaterials into hybrid structures provides a promising and flexible route to reach ultrahigh responsivity by introducing a trap‐assisted gain ( G ) mechanism. However, the high‐gain photodetectors benefitting from long carrier lifetime often possess slow response time ( t ) due to the inherent G – t tradeoff. Here, a light‐driven junction field‐effect transistor (LJFET), consisting of an n‐type ZnO belt as the channel material and a p‐type WSe 2 nanosheet as a photoactive gate material, to break the G – t tradeoff through decoupling the gain from carrier lifetime is reported. The photoactive gate material WSe 2 under illumination enables a conductive path for externally applied voltage, which modulates the depletion region within the ZnO channel efficiently. The gain and response time are separately determined by the field effect modulation and the switching speed of LJFET. As a result, a high responsivity of 4.83 × 10 3 A W −1 with a gain of ≈10 4 and a rapid response time of ≈10 µs are obtained simultaneously. The LJFET architecture offers a new approach to realize high‐gain and fast‐response photodetectors without the G – t tradeoff.

Photodetection

Nanosheet

Response time

10.1002/advs.201901637

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Citations (83)

Enhanced optical output power of blue light-emitting diodes with quasi-aligned gold nanoparticles

Nanoscale Research Letters (2014)

Yuanhao Jin Qunqing Li Guanhong Li Mo Chen Junku Liu

The output power of the light from GaN-based light-emitting diodes (LEDs) was enhanced by fabricating gold (Au) nanoparticles on the surface of p-GaN. Quasi-aligned Au nanoparticle arrays were prepared by depositing Au thin film on an aligned suspended carbon nanotube thin film surface and then putting the Au-CNT system on the surface of p-GaN and thermally annealing the sample. The size and position of the Au nanoparticles were confined by the carbon nanotube framework, and no other additional residual Au was distributed on the surface of the p-GaN substrate. The output power of the light from the LEDs with Au nanoparticles was enhanced by 55.3% for an injected current of 100 mA with the electrical property unchanged compared with the conventional planar LEDs. The enhancement may originate from the surface plasmon effect and scattering effect of the Au nanoparticles.

Nanochemistry

Optical power

10.1186/1556-276x-9-7

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Citations (22)

Interfacial Gated Graphene Photodetector with Broadband Response

ACS Applied Materials & Interfaces (2021)

Zhongzheng Huang Junku Liu Tianfu Zhang Yuanhao Jin Jiaping Wang

A much stronger interfacial gating effect was observed in the graphene/HfO2/Si photodetector when compared with that in the graphene/SiO2/Si photodetector. We found that this improvement was due to the higher interface state density at the HfO2/Si interface and the higher dielectric constant of the HfO2 layer. The photoresponsivity of the graphene/HfO2/Si photodetector is as high as 45.8 A W–1. Germanium and amorphous MoS2 (a-MoS2) were used to prepare graphene/HfO2/Ge and graphene/HfO2/a-MoS2 photodetectors, further demonstrating the high efficiency of the interfacial gating mechanism for photodetection. Because of the 0.196 eV bandgap of a-MoS2, which was verified in our previous report, the graphene/HfO2/a-MoS2 photodetector realized ultrabroadband photodetection over the range from 473 nm (visible) to 2712 nm (mid-infrared) at room temperature with photoresponsivity as high as 5.36 A W–1 and response time as fast as 68 μs, which represent significant improvements from the corresponding properties of the pure a-MoS2 photodetectors in our previous report and are comparable with those of state-of-the-art broadband photodetectors. By taking full advantage of the interfacial gating mechanism, a fast response, high photoresponsivity and ultrabroadband photodetection were achieved simultaneously. These interfacial gated graphene photodetectors also offer simple fabrication and full semiconductor process compatibility. The advantages described here indicate that the proposed photodetectors have significant potential for use in electronic and optoelectronic applications and offer a new path toward the development of ultrabroadband photodetectors.

Photodetection

10.1021/acsami.1c02738

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Citations (28)