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Dive into the research topics where Bo Lei is active.

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Featured researches published by Bo Lei.


Small | 2015

Surface Transfer Doping-Induced, High-Performance Graphene/Silicon Schottky Junction-Based, Self-Powered Photodetector

Du Xiang; Cheng Han; Zehua Hu; Bo Lei; Yiyang Liu; Li Wang; Wen Ping Hu; Wei Chen

restricted due to the local perturbations within the device depletion regions. [ 8,9 ] Self-powered photodetectors based on photovoltaic effect are able to be operated without external bias. [ 3,10–12 ] Attributed to the large existing built-in electrical potential in self-powered photodetectors, the photogenerated electron–hole pairs can be separated at zero bias and thus contribute to the photoconduction. [ 3 ]


Angewandte Chemie | 2017

Water‐Catalyzed Oxidation of Few‐Layer Black Phosphorous in a Dark Environment

Zehua Hu; Qiang Li; Bo Lei; Qionghua Zhou; Du Xiang; Zhiyang Lyu; Fang Hu; Junyong Wang; Yinjuan Ren; Rui Guo; Eda Goki; Li Wang; Cheng Han; Jinlan Wang; Wei Chen

Black phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semiconducting properties, such as thickness-dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light-induced oxidation. Herein, we report a new degradation channel via water-catalyzed oxidation of BP in the dark. When oxygen co-adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus-based devices.


Nano Letters | 2017

Surface Functionalization of Black Phosphorus via Potassium toward High-Performance Complementary Devices

Cheng Han; Zehua Hu; Lídia C. Gomes; Yang Bao; Alexandra Carvalho; Sherman Jun Rong Tan; Bo Lei; Du Xiang; Jing Wu; Dianyu Qi; Li Wang; Fengwei Huo; Wei Huang; Kian Ping Loh; Wei Chen

Two-dimensional black phosphorus configured field-effect transistor devices generally show a hole-dominated ambipolar transport characteristic, thereby limiting its applications in complementary electronics. Herein, we demonstrate an effective surface functionalization scheme on few-layer black phosphorus, through in situ surface modification with potassium, with a view toward high performance complementary device applications. Potassium induces a giant electron doping effect on black phosphorus along with a clear bandgap reduction, which is further corroborated by in situ photoelectron spectroscopy characterizations. The electron mobility of black phosphorus is significantly enhanced to 262 (377) cm2 V-1 s-1 by over 1 order of magnitude after potassium modification for two-terminal (four-terminal) measurements. Using lithography technique, a spatially controlled potassium doping technique is developed to establish high-performance complementary devices on a single black phosphorus nanosheet, for example, the p-n homojunction-based diode achieves a near-unity ideality factor of 1.007 with an on/off ratio of ∼104. Our findings coupled with the tunable nature of in situ modification scheme enable black phosphorus as a promising candidate for further complementary electronics.


ACS Nano | 2017

Electronic Properties of a 1D Intrinsic/p-Doped Heterojunction in a 2D Transition Metal Dichalcogenide Semiconductor

Zhibo Song; Thorsten Schultz; Zijing Ding; Bo Lei; Cheng Han; Patrick Amsalem; Tingting Lin; D. Z. Chi; Swee Liang Wong; Yu Jie Zheng; Ming-Yang Li; Lain-Jong Li; Wei Chen; Norbert Koch; Yu Li Huang; Andrew Thye Shen Wee

Two-dimensional (2D) semiconductors offer a convenient platform to study 2D physics, for example, to understand doping in an atomically thin semiconductor. Here, we demonstrate the fabrication and unravel the electronic properties of a lateral doped/intrinsic heterojunction in a single-layer (SL) tungsten diselenide (WSe2), a prototype semiconducting transition metal dichalcogenide (TMD), partially covered with a molecular acceptor layer, on a graphite substrate. With combined experiments and theoretical modeling, we reveal the fundamental acceptor-induced p-doping mechanism for SL-WSe2. At the 1D border between the doped and undoped SL-WSe2 regions, we observe band bending and explain it by Thomas-Fermi screening. Using atomically resolved scanning tunneling microscopy and spectroscopy, the screening length is determined to be in the few nanometer range, and we assess the carrier density of intrinsic SL-WSe2. These findings are of fundamental and technological importance for understanding and employing surface doping, for example, in designing lateral organic TMD heterostructures for future devices.


Nano Research | 2017

Significantly enhanced optoelectronic performance of tungsten diselenide phototransistor via surface functionalization

Bo Lei; Zehua Hu; Du Xiang; Junyong Wang; Goki Eda; Cheng Han; Wei Chen

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted enormous research interests and efforts towards the development of versatile electronic and optical devices, owing to their extraordinary and unique fundamental properties and remarkable prospects in nanoelectronic applications. Among the TMDs, tungsten diselenide (WSe2) exhibits tunable ambipolar transport characteristics and superior optical properties such as high quantum efficiency. Herein, we demonstrate significant enhancement in the device performance of WSe2 phototransistor by in situ surface functionalization with cesium carbonate (Cs2CO3). WSe2 was found to be strongly doped with electrons after Cs2CO3 modification. The electron mobility of WSe2 increased by almost one order of magnitude after surface functionalization with 1.6-nm-thick Cs2CO3 decoration. Furthermore, the photocurrent of the WSe2-based phototransistor increased by nearly three orders of magnitude with the deposition of 1.6-nm-thick Cs2CO3. Characterizations by in situ photoelectron spectroscopy techniques confirmed the significant surface charge transfer occurring at the Cs2CO3/WSe2 interface. Our findings coupled with the tunable nature of the surface transfer doping method establish WSe2 as a promising candidate for future 2D materialsbased optoelectronic devices.


Nature Communications | 2018

Two-dimensional multibit optoelectronic memory with broadband spectrum distinction

Du Xiang; Tao Liu; Jilian Xu; Jun Y. Tan; Zehua Hu; Bo Lei; Yue Zheng; Jing Wu; A. H. Castro Neto; Lei Liu; Wei Chen

Optoelectronic memory plays a vital role in modern semiconductor industry. The fast emerging requirements for device miniaturization and structural flexibility have diverted research interest to two-dimensional thin layered materials. Here, we report a multibit nonvolatile optoelectronic memory based on a heterostructure of monolayer tungsten diselenide and few-layer hexagonal boron nitride. The tungsten diselenide/boron nitride memory exhibits a memory switching ratio approximately 1.1 × 106, which ensures over 128 (7 bit) distinct storage states. The memory demonstrates robustness with retention time over 4.5 × 104 s. Moreover, the ability of broadband spectrum distinction enables its application in filter-free color image sensor. This concept is further validated through the realization of integrated tungsten diselenide/boron nitride pixel matrix which captured a specific image recording the three primary colors (red, green, and blue). The heterostructure architecture is also applicable to other two-dimensional materials, which is confirmed by the realization of black phosphorus/boron nitride optoelectronic memory.Continued device miniaturization and feasibility of integrating two-dimensional materials into circuits have enabled flexible and transparent optoelectronic memories. Here, the authors show a WSe2–hBN-based heterostructure memory with switching ratio of ~1.1 × 106, ensuring over 128 distinct storage states and retention time of ~4.5 × 104 s.


Advanced Materials | 2018

Abnormal Near-Infrared Absorption in 2D Black Phosphorus Induced by Ag Nanoclusters Surface Functionalization

Zehua Hu; Qiang Li; Bo Lei; Jing Wu; Qionghua Zhou; Chengding Gu; Xinglin Wen; Junyong Wang; Yanpeng Liu; Shisheng Li; Yue Zheng; Junpeng Lu; Jun He; Li Wang; Qihua Xiong; Jinlan Wang; Wei Chen

Black phosphorus (BP), as a fast emerging 2D material, shows promising potential in near-infrared (NIR) photodetection owing to its relatively small direct thickness-dependent bandgaps. However, the poor NIR absorption due to the atomically thin nature strongly hinders the practical application. In this study, it is demonstrated that surface functionalization of Ag nanoclusters on 2D BP can induce an abnormal NIR absorption at ≈746 nm, leading to ≈35 (138) times enhancement in 808 (730) nm NIR photoresponse for BP-based field-effect transistors. First-principles calculations reveal that localized bands are introduced into the bandgap of BP, serving as the midgap states, which create new transitions to the conduction band of BP and eventually lead to the abnormal absorption. This work provides a simple yet effective method to dramatically increase the NIR absorption of BP, which is crucial for developing high-performance NIR optoelectronic devices.


Nano Research | 2018

Emergence of photoluminescence on bulk MoS 2 by laser thinning and gold particle decoration

Lili Gong; Qi Zhang; Liangjun Wang; Jianfeng Wu; Cheng Han; Bo Lei; Wei Chen; Goki Eda; K. E. J. Goh; Chorng Haur Sow

We demonstrate a facile and effective approach to significantly improve the photoluminescence of bulk MoS2 via laser thinning followed by gold particle decoration. Upon laser thinning of exfoliated bulk MoS2, photoluminescence emerges from the laser-thinned region. After further treatment with an AuCl3 solution, gold particles self-assemble on the laser-thinned region and thick edges, further increasing the fluorescence of bulk MoS2 28 times and the Raman response 3 times. Such fluorescence enhancement can be attributed to both surface plasmon resonance and p-type doping induced by gold particles. The combination of laser thinning and AuCl3 treatment enables the functionalization of bulk MoS2 for optoelectronic applications. It can also provide a viable strategy for mask-free and area-selective p-type doping on single MoS2 flakes.


2D Materials | 2017

Oxygen induced strong mobility modulation in few-layer black phosphorus

Cheng Han; Zehua Hu; Alexandra Carvalho; Na Guo; Jialin Zhang; Fang Hu; Du Xiang; Jing Wu; Bo Lei; Li Wang; Chun Zhang; A. H. Castro Neto; Wei Chen


ACS Nano | 2018

Direct Observation of Semiconductor-Metal Phase Transition in Bilayer Tungsten Diselenide Induced by Potassium Surface Functionalization

Bo Lei; Yuanyuan Pan; Zehua Hu; Jialin Zhang; Du Xiang; Yue Zheng; Rui Guo; Cheng Han; Lianhui Wang; Jing Lu; Li Yang; Wei Chen

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Zehua Hu

National University of Singapore

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Cheng Han

National University of Singapore

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Du Xiang

National University of Singapore

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Wei Chen

National University of Singapore

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Jing Wu

National University of Singapore

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Junyong Wang

National University of Singapore

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Yue Zheng

National University of Singapore

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Wei Chen

National University of Singapore

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Jialin Zhang

National University of Singapore

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