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Towards high-mobility In2xGa2-2xO3 nanowire field-effecttransistors

Nano Research 2018年第11期11卷 5935-5945页

作者： Ziyao Zhou Changyong Lan senpo yip Renjie Wei Dapan Li Lei Shu Johnny C. Ho Department of Materials Science and Engineering City University of Hong Kong Kowloon Hong Kong 999077 China School of Optoelectronic Science and Engineering University of Electronic Science and Technology of China Chengdu 610054 China Shenzhen Research Institute City University of Hang Kong Shenzhen S 18057 China State Key Laboratory of Millimeter Waves City University of Hang Kong Kowloon Hang Kong 999077 China

Recently, owing to the excellent electrical and optical properties, n-type In2O3 nanowires (NWs) have attracted tremendous attention for application in memory devices, solar cells, and ultra-violet photodetectors. However, the relatively low electron mobility of In2O3 NWs grown by chemical vapor deposition (CVD) has limited their further utilization. In this study, utilizing in-situ Ga alloying, highly crystalline, uniform, and thin In2xGa2−2xO3 NWs with diameters down to 30 nm were successfully prepared via ambient-pressure CVD. Introducing an optimal amount of Ga (10 at.%) into the In2O3 lattice was found to effectively enhance the crystal quality and reduce the number of oxygen vacancies in the NWs. A further increase in the Ga concentration adversely induced the formation of a resistive β-Ga2O3 phase, thereby deteriorating the electrical properties of the NWs. Importantly, when configured into global back-gated NW field-effect transistors, the optimized In1.8Ga0.2O3 NWs exhibit significantly enhanced electron mobility reaching up to 750 cm2·V–1·s–1 as compared with that of the pure In2O3 NW, which can be attributed to the reduction in the number of oxygen vacancies and ionized impurity scattering centers. Highly ordered NW parallel arrayed devices were also fabricated to demonstrate the versatility and potency of these NWs for next-generation, large-scale, and high-performance nanoelectronics, sensors, etc.

关键词： In_2O_3 In_(2x)Ga_(2–2x)O_3 nanowire chemical vapor deposition mobility oxygen vacancy

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The origin of gate bias stress instability and hysteresis in monolayer WS2 transistors

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Nano Research 2020年第12期13卷 3278-3285页

作者： Changyong Lan Xiaolin Kang You Meng Renjie Wei Xiuming Bu senpo yip Johnny C.Ho State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu610054China School of Optoelectronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu610054China Department of Materials Science and Engineering City University of Hong KongKowloonHong Kong999077China State Key Laboratory of Terahertz and Millimeter Waves City University of Hong KongKowloonHong Kong999077China Key Laboratory of Advanced Materials Processing&Mold of Ministry of Education Zhengzhou UniversityZhengzhou450002China

Due to the ultra-thin nature and moderate carrier mobility,semiconducting two-dimensional(2D)materials have attracted extensive attention for next-generation ***,the gate bias stress instability and hysteresis are always observed in these 2D materials-based transistors that significantly degrade their reliability for practical ***,the origin of gate bias stress instability and hysteresis for chemical vapor deposited monolayer WS2 transistors are investigated *** transistor performance is found to be strongly affected by the gate bias stress time,sweeping rate and range,and *** on the systematical study and complementary analysis,charge trapping is determined to be the major contribution for these observed ***,due to these charge trapping effects,the channel current is observed to decrease with time;hence,a rate equation,considering the charge trapping and time decay effect of current,is proposed and developed to model the phenomena with excellent consistency with experimental *** these results do not only indicate the validity of the charge trapping model,but also confirm the hysteresis being indeed caused by charge ***,this simple model provides a sufficient explanation for the charge trapping induced gate bias stress instability and hysteresis in monolayer WS2 transistors,which can be also applicable to other kinds of transistors.

关键词： charge trapping gate bias stress instability hysteresis WS2 transistor

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Direct drop-casting synthesis of all-inorganic lead and lead-free halide perovskite microcrystals for high-performance photodetectors

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Nano Research 2022年第4期15卷 3621-3627页

作者： Zhengxun Lai You Meng Fei Wang Xiuming Bu Wei Wang Pengshan Xie Weijun Wang Chuntai Liu senpo yip Johnny C.Ho Department of Materials Science and Engineering City University of Hong KongKowloonHong Kong 999077China State Key Laboratory of Luminescence and Applications Changchun Institute of OpticsFine Mechanics and PhysicsChinese Academy of SciencesChangchun 130021China State Key Laboratory of Terahertz and Millimeter Waves City University of Hong KongKowloonHong Kong 999077China Key Laboratory of Advanced Materials Processing&Mold(Zhengzhou University) Ministry of EducationZhengzhou 450002China Institute for Materials Chemistry and Engineering Kyushu UniversityFukuoka 816–8580Japan

Due to the exciting photoelectric properties,better stability,and environmental-friendly nature,all-inorganic halide perovskites(AIHPs),especially the lead-free perovskites,have attracted worldwide ***,the film quality of AIHPs fabricated by typical spin-coating and subsequent high-temperature annealing is still not satisfactory,restricting their further ***,we demonstrate a simple low-temperature solution-processed drop-casting method to achieve highly-crystalline cubic CsPbBr_(3)and lead-free layer-structured Cs_(3)Sb_(2)I_(9)microcrystals(MCs).This drop-casting technique not only consumes the less amount of precursor solution but also eliminates the high-temperature annealing as compared with those of spin *** these MCs are configured into photodetectors,they exhibit superior device performance,which is in distinct contrast to the one of spin-coated ***,the responsivity of CsPbBr_(3)MCs is found to be as large as 8,990 mA/W,being 13 times larger than the spin-coated films and even better than many state-of-the-art solution-processed AIHPs *** device performance enhancement is attributed to the better film quality and phase purity obtained by the drop-casting *** these results can evidently fill the“technology gap”for further enhancing the material quality of solution-processed AIHPs and breaking down the barriers that hinder the development of AIHPs based optoelectronic devices.

关键词： halide perovskite drop-casting photodetector CsPbBr_(3) Cs_(3)Sb_(2)I_(9)

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Wafer-scale synthesis of monolayer WS2 for high-performance flexible photodetectors by enhanced chemical vapor deposition

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Nano Research 2018年第6期11卷 3371-3384页

作者： Changyong Lan Ziyao Zhou Zhifei Zhou Chun Li Lei Shu Lifan Shen Dapan Li Ruoting Dong senpo yip Johnny C. Ho Department of Materials Science and Engineering City University of Hong Kong Hong Kong 999077 China School of Optoelectronic Information University of Electronic Science and Technology of China Chengdu 610054 China Shenzhen Research Institute City University of Hong Kong Shenzhen 518057 China State Key Laboratory of Millimeter Waves City University of Hong Kong Kowloon Hong Kong 999077 China Centre for Functional Photonics City University of Hong Kong Kowloon Hong Kong 999077 China

Two-dimensional （2D） nanomaterials have recently attracted considerable attention due to their promising applications in next-generation electronics and optoelectronics. In particular, the large-scale synthesis of high-quality 2D materials is an essential requirement for their practical applications. Herein, we demonstrate the wafer-scale synthesis of highly crystalline and homogeneous monolayer WS2 by an enhanced chemical vapor deposition （CVD） approach, in which precise control of the precursor vapor pressure can be effectively achieved in a multi-temperature zone horizontal furnace. In contrast to conventional synthesis methods, the obtained monolayer WS2 has excellent uniformity both in terms of crystallinity and morphology across the entire substrate wafer grown （e.g., 2 inches in diameter）, as corroborated by the detailed characterization. When incorporated in typical rigid photodetectors, the monolayer WS2 leads to a respectable photodetection performance, with a responsivity of 0.52 mA/W, a detectivity of 4.9 × 10^9 Jones, and a fast response speed （〈 560μs）. Moreover, once fabricated as flexible photodetectors on polyimide, the monolayer WS2 leads to a responsivity of up to 5 mA/W. Importantly, the photocurrent maintains 89% of its initial value even after 3,000 bending cycles. These results highlight the versatility of the present technique, which allows its applications in larger substrates, as well as the excellent mechanical flexibility and robustness of the CVD-grown, homogenous WS2 monolayers, which can promote the development of advanced flexible optoelectronic devices.

关键词： wafer-scale WS2 monolayer chemical vapor deposition flexible optoelectronics

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Crystalline InGaZnO quaternary nanowires with superlattice structure for high-performance thin-film transistors

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Nano Research 2019年第8期12卷 1796-1803页

作者： Fangzhou Li senpo yip Ruoting Dong Ziyao Zhou Changyong Lan Xiaoguang Liang Dapan Li You Meng Xiaolin Kang Johnny C. Ho Department of Materials Science and Engineering City University of Hong KongHong Kong 999077China Shenzhen Research Institute City University of Hong Kong Shenzhen 518057China State Key Laboratory of Terahertz and Millimeter Waves City University of Hong Kong Hong Kong 999077China Centre for Functional Photonics City University of Hong Kong Hong Kong 999077China

Amorphous indium-gallium-zinc oxide (a-IGZO) materials have been widely explored for various thin-film transistor (TFT) applications;however, their device performance is still restricted by the intrinsic material issues especially due to their non-crystalline nature. In this study, highly crystalline superlattice-structured IGZO nanowires (NWs) with different Ga concentration are successfully fabricated by enhanced ambient-pressure chemical vapor deposition (CVD). The unique superlattice structure together with the optimal Ga concentration (i.e., 31 at.%) are found to effectively modulate the carrier concentration as well as efficiently suppress the oxygen vacancy formation for the superior NW device performance. In specific, the In1.8Ga1.8Zn2.4O7 NW field-effect transistor exhibit impressive device characteristics with the average electron mobility of ~ 110 cm^2-V^-1·s^-1 and on/off current ratio of ~ 10^6. Importantly, these NWs can also be integrated into NW parallel arrays for the construction of high-performance TFT devices, in which their performance is comparable to many state-of-the-art IGZO TFTs. All these results can evidently indicate the promising potential of these crystalline superlattice-structured IGZO NWs for the practical utilization in next-generation metal-oxide TFT device technologies.

关键词： InGaZnO nanowires thin-film transistors superlattice

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High-performance photodetectors based on two-dimensional perovskite crystals with alternating interlayer cations

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Journal of Materiomics 2023年第4期9卷 817-823页

作者： Yezhan Li Zhengxun Lai You Meng Wei Wang Yuxuan Zhang Xuwen Zhao Di Yin Weijun Wang Pengshan Xie Quan Quan senpo yip Johnny C.Ho Department of Materials Science and Engineering City University of Hong Kong999077Hong Kong SARChina Institute for Materials Chemistry and Engineering Kyushu UniversityFukuoka816-8580Japan State Key Laboratory of Terahertz and Millimeter Waves City University of Hong Kong999077Hong Kong SARChina

Organic-inorganic halide perovskite,as a low-cost,solution-processable material with remarkable optoelectronic properties,is ideal candidate to fabricate high-performance photodetectors and is expected to significantly reduce device *** to the common Dion-Jacobson and Ruddlesden-Popper two-dimensional(2D)layered hybrid perovskite compounds,the perovskites with alternating cations in the interlayer(ACI)phase show higher crystal symmetry and narrower optical bandgaps,which exhibit great potential for excellent photodetection ***,we report a high-performance photodetector based on the 2D bilayered hybrid lead halide perovskite single crystal with the ACI phase(GAMA_(2)Pb_(2)I_(7);GA=C(NH_(2))_(3)and MA=CH_(3)NH_(3)).The single-crystal photodetector exhibits high photoresponsivity of 1.56,2.54,and 2.60 A/W for incident light wavelengths of 405,532,and 635 nm under 9.82 nW,respectively,together with the correspondingly high detectivity values of 1.86×10^(12),3.04×10^(12),and 3.11×10^(12)Jones under the same operating ***,a high-resolution imaging sensor is built based on the GAMA_(2)Pb_(2)I_(7)single-crystal photodetector,confirming the high stability and photosensitivity of the imaging *** results show that the 2D hybrid lead halide perovskites with alternating interlayer cations are promising for high-performance visible light photodetectors and imaging systems.

关键词： Photodetector Two-dimensional Hybrid perovskite Alternating interlayer cation Imaging

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Recent advances in flexible photodetectors based on 1D nanostructures

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Journal of Semiconductors 2019年第11期40卷 13-29页

作者： senpo yip Lifan Shen Johnny C Ho Department of Materials Science and Engineering City University of Hong KongHong KongChina Shenzhen Research Institute City University of Hong KongShenzhen 518057China College of Microelectronics and Key Laboratory of Optoelectronics Technology Faculty of Information TechnologyBeijing University of TechnologyBeijing 100124China

Semiconductor nanowires have demonstrated excellent electronic and optoelectronic *** integrated into photodetectors,excellent device performance can be easily *** from the exceptional performance,these nanowires can also enable robust and mechanically flexible photodetectors for various advanced utilizations that the rigid counterparts cannot *** unique applications include personal healthcare,next-generation robotics and many *** this review,we would first discuss the nanowire fabrication techniques as well as the assembly methods of constructing largescale nanowire ***,the recent development of flexible photodetectors based on these different nanowire material systems is evaluated in *** the same time,we also introduce some recent advancement that allows individual photodetectors to integrate into a more complex system for advanced ***,a short conclusion and outlook of challenges faced in the future of the community is presented.

关键词： nanowires flexible photodetectors

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Solution-processed lead-free double perovskite microplatelets with enhanced photoresponse and thermal stability

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Science China Materials 2022年第5期65卷 1313-1319页

作者： Zhengxun Lai Fei Wang You Meng Xiuming Bu Xiaolin Kang Quan Quan Wei Wang senpo yip Chuntai Liu Johnny C.Ho Department of Materials Science and Engineering City University of Hong KongKowloon 999077Hong Kong SARChina State Key Laboratory of Luminescence and Applications Changchun Institute of OpticsFine Mechanics and PhysicsChinese Academy of SciencesChangchun 130021China State Key Laboratory of Terahertz and Millimeter Waves City University of Hong KongKowloon 999077Hong Kong SARChina Institute for Materials Chemistry and Engineering Kyushu UniversityFukuoka 816-8580Japan Key Laboratory of Advanced Materials Processing&Mold(Ministry of Education) Zhengzhou UniversityZhengzhou 450002China

Due to the better stability and environmentfriendly nature,lead-free halide double perovskites are widely explored as promising materials for next-generation photovoltaics and optoelectronics;however,to date,their photoelectric device performance is still not ***,we report a facile solution-process method to synthesize the recently most popular lead-free halide double perovskite,MA_(2)Ag Bi Br_(6),and its all-inorganic counterpart,Cs_(2)Ag Bi Br_(6).The obtained MA_(2)Ag Bi Br_(6)and Cs_(2)Ag Bi Br_(6)films exhibit the microplatelet morphology with excellent crystallinity,distinctly contrasting the ones fabricated by the conventional spin-coating *** fabricated into simple photodetectors,the Cs_(2)Ag Bi Br_(6)microplatelet devices yield a respectable responsivity of 245 m A W^(-1) that is two orders of magnitude larger than that of the spin-coated *** importantly,the response speed of the Cs_(2)Ag Bi Br_(6)microplatelets device is as fast as 145μs,which is higher than most of the values reported in the community of halide double *** subjected to the thermal stability testing,the Cs_(2)Ag Bi Br_(6)microplatelet device can maintain its initial performance after heating to 160℃ and cooling down to room temperature in the ambient *** these results suggest that the facile solution-process method is capable of fabricating high-quality lead-free double perovskites,enabling their advanced device applications.

关键词： lead-free double perovskite Cs_(2)AgBiBr_(6) MA_(2)AgBiBr_(6) thermal stability photodetector

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Better Use of Data to Define Nutrition Priority and Action

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Biomedical and Environmental Sciences 2001年第1期14卷 61-65页

作者： RAY yip Senior Adviser Health Nutrition UNICEF Area Office for China and Mongolia

Nutrition and dietary survey data has been useful in defining the magnitude of malnutrition and dietary deficit. Such information has been helpful in gaining attention to support or to do more to improve nutrition advocacy. However, there are also greater opportunities to use the common data to guide the program action. In summary, we have plenty of good nutrition and dietary information available to us in the planning and operation of nutrition intervention program. If we go beyond the use of data to justify area or subject of engagement, we can also use the same data for more efficient and more effective program without additional cost to us.

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Pathological mechanisms and therapeutic strategies for Alzheimer's disease

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Neural Regeneration Research 2022年第3期17卷 543-549页

作者： Yaojun Ju Kin yip Tam Faculty of Health Sciences University of MacaoAvenida de UniversidadeTaipaMacao Special Adiministrative RegionChina

Alzheimer's disease is a rather complex neurodegenerative disease,which is attributed to a combination of multiple *** the many pathological pathways,synaptic dysfunctions,such as synapses loss and deficits in synaptic plasticity,were thought to be strongly associated with cognitive *** deficiencies in various sorts of neurotransmissions are responsible for the multifarious neurodegenerative symptoms in Alzheimer's disease,for example,the cholinergic and glutamatergic deficits for cognitive decline,the excitatory and inhibitory neurotransmission dyshomeostasis for synaptic plasticity deficits and epileptiform symptoms,and the monoamine neurotransmission for neuropsychiatric *** cascade hypothesis is the most popular pathological theory to explain Alzheimer's disease pathogenesis and attracts considerable *** lines of genetic and pathological evidence support the predominant role of amyloid beta in Alzheimer's disease *** tangles assembled by microtubule-associated protein tau are other important histopathological characteristics in Alzheimer's disease *** of tau toxicity was proved to lead to neuron damage,neuroinflammation and oxidative stress in *** is the main risk factor of neurodegenerative diseases,and is associated with inflammation,oxidative stress,reduced metabolism,endocrine insufficiencies and organ *** aging related risk factors were also proved to be some of the risk factors contributing to Alzheimer's *** Alzheimer's disease drug development,many good therapeutic strategies have been investigated in clinical ***,complex mechanism of Alzheimer's disease and the interplay among different pathological factors call for the come out of allpowerful therapies with multiple curing *** review seeks to summarize some of the representative treatments targeting different pathological pathways currently under clinical ***

关键词： Alzheimer's disease pathological pathways drug development multiple pathologies

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