Zhu Chun Xiang

@article{ISI:000479319100017,
title = {Electronic Devices and Circuits Based on Wafer-Scale Polycrystalline Monolayer MoS_{2} by Chemical Vapor Deposition},
author = {Lin Wang and Li Chen and Swee Liang Wong and Xin Huang and Wugang Liao and Chunxiang Zhu and Yee-Fun Lim and Dabing Li and Xinke Liu and Dongzhi Chi and Koh-Wee Ang},
doi = {10.1002/aelm.201900393},
times_cited = {78},
issn = {2199-160X},
year = {2019},
date = {2019-08-01},
journal = {ADVANCED ELECTRONIC MATERIALS},
volume = {5},
number = {8},
publisher = {WILEY},
address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA},
abstract = {2D layered materials such as graphene and transition-metal dichalcogenides (TMDCs) have emerged as promising candidates for next-generation nanoelectronic applications due to their atomically thin thicknesses and unique electronic properties. Among TMDCs, molybdenum disulfide (MoS2) has been extensively investigated as a channel material for field-effect transistor (FET) and circuit realization. However, to date most reported works have been limited to exfoliated MoS2 nanosheets primarily due to the difficulty in synthesizing large-area and high-quality MoS2 thin film. A demonstration of wafer-scale monolayer MoS2 synthesis is reported by chemical vapor deposition (CVD), enabling transistors, memristive memories, and integrated circuits to be realized simultaneously. Specifically, building on top-gated FETs with a high-kappa gate dielectric (HfO2), Boolean logic circuits including inverters and NAND gates are successfully demonstrated using direct-coupled FET logic technology, with typical inverters exhibiting a high voltage gain of 16, a large total noise margin of 0.72 V-DD at V-DD = 3 V, and perfect logic-level matching. Additionally, resistive switching is demonstrated in a MoS2-based memristor, indicating that they have great potential for the development of resistive random-access memory. By virtue of scalable CVD growth capability, the way toward practical and large-scale electronic applications of MoS2 is indicated.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000472552900004,
title = {Artificial Synapses Based on Multiterminal Memtransistors for Neuromorphic Application},
author = {Lin Wang and Wugang Liao and Swee Hang Wong and Zhi Gen Yu and Sifan Li and Yee-Fun Lim and Xuewei Feng and Wee Chong Tan and Xin Huang and Li Chen and Liang Liu and Jingsheng Chen and Xiao Gong and Chunxiang Zhu and Xinke Liu and Yong-Wei Zhang and Dongzhi Chi and Kah-Wee Ang},
doi = {10.1002/adfm.201901106},
times_cited = {225},
issn = {1616-301X},
year = {2019},
date = {2019-06-01},
journal = {ADVANCED FUNCTIONAL MATERIALS},
volume = {29},
number = {25},
publisher = {WILEY-V C H VERLAG GMBH},
address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY},
abstract = {Neuromorphic computing, which emulates the biological neural systems could overcome the high-power consumption issue of conventional von-Neumann computing. State-of-the-art artificial synapses made of two-terminal memristors, however, show variability in filament formation and limited capacity due to their inherent single presynaptic input design. Here, a memtransistor-based arti?cial synapse is realized by integrating a memristor and selector transistor into a multiterminal device using monolayer polycrys-talline-MoS2 grown by a scalable chemical vapor deposition (CVD) process. Notably, the memtransistor offers both drain- and gate-tunable nonvolatile memory functions, which efficiently emulates the long-term potentiation/depression, spike-amplitude, and spike-timing-dependent plasticity of biological synapses. Moreover, the gate tunability function that is not achievable in two-terminal memristors, enables significant bipolar resistive states switching up to four orders-of-magnitude and high cycling endurance. First-principles calculations reveal a new resistive switching mechanism driven by the diffusion of double sulfur vacancy perpendicular to the MoS2 grain boundary, leading to a conducting switching path without the need for a filament forming process. The seamless integration of multiterminal memtransistors may offer another degree-of-freedom to tune the synaptic plasticity by a third gate terminal for enabling complex neuromorphic learning.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000460664000028,
title = {Unipolar n-Type Conduction in Black Phosphorus Induced by Atomic Layer Deposited MgO},
author = {Lin Wang and Wugang Liao and Shengqiang Xu and Xiao Gong and Chunxiang Zhu and Kah-Wee Ang},
doi = {10.1109/LED.2019.2895678},
times_cited = {9},
issn = {0741-3106},
year = {2019},
date = {2019-03-01},
journal = {IEEE ELECTRON DEVICE LETTERS},
volume = {40},
number = {3},
pages = {471-474},
publisher = {IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC},
address = {445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA},
abstract = {Two-dimensional black phosphorus (BP) holds great promise for future nanoscale field-effect transistors owing to its finite bandgap and expected high carrier mobility. Nevertheless, while most studies have reported unipolar p-type or ambipolar BP transistors with a hole conduction dominance, excellent n-type transport in BP has been a critical challenge. Here, we report unipolar n-type BP transistors realized by a MgO capping layer via atomic layer deposition. By coveragewith 20-nm-thick-MgO, remarkable electron conduction is obtained in transistors fabricated on BP flakes of thicknesses from 2.6 to 7.6 nm, accompanied by fully suppressed hole transport. Furthermore, the unipolar electron transport is found to retain (or even improve) after a period of six months, with the highest extrinsic electron mobility reaching 135.9 cm(2)/Vs. The effective approach to realizing unipolar n-FETs of BP demonstrated in this letter paves the way to the implementation of BP-basedCMOS digital logic circuits.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000456749900095,
title = {Waveguide-Integrated Black Phosphorus Photodetector for Mid-Infrared Applications},
author = {Li Huang and Bowei Dong and Xin Guo and Yuhua Chang and Nan Chen and Xin Huang and Wugang Liao and Chunxiang Zhu and Hong Wang and Chengkuo Lee and Kah-Wee Ang},
doi = {10.1021/acsnano.8b08758},
times_cited = {198},
issn = {1936-0851},
year = {2019},
date = {2019-01-01},
journal = {ACS NANO},
volume = {13},
number = {1},
pages = {913-921},
publisher = {AMER CHEMICAL SOC},
address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
abstract = {Midinfrared (MIR), which covers numerous molecular vibrational fingerprints, has attracted enormous research interest due to its promising potential for label-free and damage-free sensing. Despite intense development efforts, the realization of waveguide-integrated on-chip sensing system has seen very limited success to date. The huge lattice mismatch between silicon and the commonly used detection materials such as HgCdTe, III-V, or II-VI compounds has been the key bottleneck that hinders their integration. Here, we realize an integration of silicon-on insulator (SOI) waveguides with black phosphorus (BP) photodetectors. When operating near BP's cutoff wavelength where absorption is weak, the light-BP interaction is enhanced by exploiting the optical confinement in the Si waveguide and grating structure to overcome the limitation of absorption length constrained by the BP thickness. Devices with different BP crystal orientation and thickness are compared in terms of their responsivity and noise equivalent power (NEP). Spectral photoresponse from 3.68 to 4.03 mu m was investigated. Additionally, power-dependent responsivity and gate-tunable photocurrent were also studied. At a bias of 1 V, the BP photodetector achieved a responsivity of 23 A/W at 3.68 mu m and 2 A/W at 4 mu m and a NEP less than 1 nW/Hz(1/2) at room temperature. The integration of passive Si photonics and active BP photodetector is envisaged to offer a potential pathway toward the realization of integrated on-chip systems for MIR sensing applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000450932100006,
title = {Efficient and reliable surface charge transfer doping of black phosphorus via atomic layer deposited MgO toward high performance complementary circuits},
author = {Wugang Liao and Lin Wang and Li Chen and Wei Wei and Zhe Zeng and Xuewei Feng and Li Huang and Wee Chong Tan and Xin Huang and Kah Wee Ang and Chunxiang Zhu},
doi = {10.1039/c8nr04420a},
times_cited = {33},
issn = {2040-3364},
year = {2018},
date = {2018-09-26},
journal = {NANOSCALE},
volume = {10},
number = {36},
pages = {17007-17014},
publisher = {ROYAL SOC CHEMISTRY},
address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND},
abstract = {Black phosphorus (BP), a fast emerging 2D material, has shown great potential in future electronics and optoelectronics owing to its outstanding properties including sizable band gap and ambipolar transport characteristics. However, its hole conduction dominance, featured by a much larger hole mobility and the corresponding on-current than that of the electrons, renders the reliable modulation of its carrier type and density a key challenge, thereby hindering its application to complementary electronics. Here, we demonstrate an efficient and reliable n-type doping for BP transistors via surface functionalization by atomic layer deposited magnesium oxide (MgO) with favorable controllability. By optimizing the MgO thickness, an electron mobility of up to 95.5 cm(2) V-1 s(-1) is reached with a simultaneous significant suppression of hole conduction. Subsequently, a high-performance complementary logic inverter is demonstrated within a single BP flake, which operates well with a supply voltage as low as <0.5 V, outperforming reported BP inverters in terms of logic level match, power consumption and process feasibility. Our findings suggest that surface charge transfer doping via MgO can be used as a promising technique towards high performance BP-based functional nanoelectronics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000426618000052,
title = {Low-Frequency Noise in Layered ReS_{2} Field Effect Transistors on HfO_{2} and Its Application for pH Sensing},
author = {Wugang Liao and Wei Wei and Yu Tong and Wai Kin Chim and Chunxiang Zhu},
doi = {10.1021/acsami.8b00193},
times_cited = {63},
issn = {1944-8244},
year = {2018},
date = {2018-02-28},
journal = {ACS APPLIED MATERIALS & INTERFACES},
volume = {10},
number = {8},
pages = {7248-7255},
publisher = {AMER CHEMICAL SOC},
address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
abstract = {Layered rhenium disulfide (ReS2) field effect transistors (FETs), with thickness ranging from few to dozens of layers, are demonstrated on 20 nm thick HfO2/Si substrates. A small threshold voltage of -0.25 V, high on/off current ratio of up to similar to 10(7), small subthreshold swing of 116 mV/dec, and electron carrier mobility of 6.02 cm(2)/V.s are obtained for the two-layer ReS2 FETs. Low-frequency noise characteristics in ReS2 FETs are analyzed for the first time, and it is found that the carrier number fluctuation mechanism well describes the flicker (18) noise of ReS2 FETs with different thicknesses. pH sensing using a two-layer ReS2 FET with HfO2 as a sensing oxide is then demonstrated with a voltage sensitivity of 54.8 mV/pH and a current sensitivity of 126. The noise characteristics of the ReS2 FET-based pH sensors are also examined, and a corresponding detection limit of 0.0132 pH is obtained. Our studies suggest the high potential of ReS2 for future low-power nanoelectronics and biosensor applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}