Recently, owing to the excellent electrical and optical properties, n-type In203nanowires （NWs） have attracted tremendous attention for application in memorydevices, solar cells, and ultra-violet photodetectors. How...Recently, owing to the excellent electrical and optical properties, n-type In203nanowires （NWs） have attracted tremendous attention for application in memorydevices, solar cells, and ultra-violet photodetectors. However, the relatively lowelectron mobility of In203 NWs grown by chemical vapor deposition （CVD） haslimited their further utilization. In this study, utilizing in-situ Ga alloying,highly crystalline, uniform, and thin In2xGa2-2xO3 NWs with diameters down to30 nm were successfully prepared via ambient-pressure CVD. Introducing anoptimal amount of Ga （10 at.%） into the In2O3 lattice was found to effectivelyenhance the crystal quality and reduce the number of oxygen vacancies in theNWs. A further increase in the Ga concentration adversely induced the formationof a resistive β-Ga203 phase, thereby deteriorating the electrical properties ofthe NWs. Importantly, when configured into global back-gated NW field-effecttransistors, the optimized Inl.8Ga0.2O3 NWs exhibit significantly enhanced electronmobility reaching up to 750 cm2.V-l.s^-1 as compared with that of the pure In203NW, which can be attributed to the reduction in the number of oxygen vacanciesand ionized impurity scattering centers. Highly ordered NW parallel arrayeddevices were also fabricated to demonstrate the versatility and potency of theseNWs for next-generation, large-scale, and high-performance nanoelectronics,sensors, etc.展开更多
We report an erbium-doped fiber laser passively Q-switched by a few-layer molybdenum disulfide（MoS2） saturable absorber（SA）.The few-layer MoS2 is grown by the chemical vapor deposition method and transferred onto ...We report an erbium-doped fiber laser passively Q-switched by a few-layer molybdenum disulfide（MoS2） saturable absorber（SA）.The few-layer MoS2 is grown by the chemical vapor deposition method and transferred onto the end-face of a fiber connector to form a fiber-compatible MoS2 SA.The laser cavity is constructed by using a three-port optical circulator and a fiber Bragg grating（FBG） as the two end-mirrors.Stable Q-switched pulses are obtained with a pulse duration of 1.92 μs at 1560.5 nm.By increasing the pump power from 42 to 204 mW,the pulse repetition rate can be widely changed from 28.6 to 114.8 kHz.Passive Q-switching operations with discrete lasing wavelengths ranging from 1529.8 to 1570.1 nm are also investigated by using FBGs with different central wavelengths.This work demonstrates that few-layer MoS2 can serve as a promising SA for wideband-tunable Q-switching laser operation.展开更多
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 issu...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.展开更多
Due to the ultra-thin nature and moderate carrier mobility,semiconducting two-dimensional(2D)materials have attracted extensive attention for next-generation electronics.However,the gate bias stress instability and hy...Due to the ultra-thin nature and moderate carrier mobility,semiconducting two-dimensional(2D)materials have attracted extensive attention for next-generation electronics.However,the gate bias stress instability and hysteresis are always observed in these 2D materials-based transistors that significantly degrade their reliability for practical applications.Herein,the origin of gate bias stress instability and hysteresis for chemical vapor deposited monolayer WS2 transistors are investigated carefully.The transistor performance is found to be strongly affected by the gate bias stress time,sweeping rate and range,and temperature.Based on the systematical study and complementary analysis,charge trapping is determined to be the major contribution for these observed phenomena.Importantly,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 data.All these results do not only indicate the validity of the charge trapping model,but also confirm the hysteresis being indeed caused by charge trapping.Evidently,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.展开更多
Two-dimensional transition metal dichalcogenides(TMDs)are needed in highperformance piezoresistive sensors due to their strong strain-induced bandgap modification and thereby large gauge factors.However,integrating a ...Two-dimensional transition metal dichalcogenides(TMDs)are needed in highperformance piezoresistive sensors due to their strong strain-induced bandgap modification and thereby large gauge factors.However,integrating a conventional high-temperature chemical vapor deposition(CVD)-grown TMD with a flexible substrate necessitates a transfer process that inevitably degrades the sensing properties of the TMDs and increases the overall fabrication complexity.We present a high-performance piezoresistive strain sensor that employs largearea PdSe_(2) films grown directly on polyimide(PI)substrates via plasma-assisted selenization of a sputtered Pd film.The reliable strain transfer from the substrate to the PdSe_(2) film ensures an outstanding strain-sensing capability of the sensor.Specifically,the sensors have a gauge factor of up to315±2.1,a response time under 25 ms,a detection limit of 8×10^(-6),and an exceptional stability of over 104 loadingunloading cycles.By attaching the sensors to the skin surface,we demonstrate their application for measuring physiological parameters in health care monitoring,including motion,voice,and arterial pulse vibration.Furthermore,using the PdSe_(2) film sensor combined with deep learning technology,we achieved intelligent recognition of artery temperature from arterial pulse signals with only a 2%difference between predicted and actual temperatures.The excellent sensing performance,together with the advantages of low-temperature fabrication and simple device structure,make the PdSe_(2) film sensor promising for wearable electronics and health care sensing systems.展开更多
基金We acknowledge the General Research Fund （No. CityU 11275916） and the Theme-based Research Scheme （No. T42-103/16-N） of the Research Grants Council of Hong Kong SAR, China, the National Natural Science Foundation of China （Nos. 51672229 and 61605024）, the Science Technology and Innovation Committee of Shenzhen Municipality （No. JCYJ20160229165240684） and a grant from the Shenzhen Research Institute, City University of Hong Kong.
文摘Recently, owing to the excellent electrical and optical properties, n-type In203nanowires （NWs） have attracted tremendous attention for application in memorydevices, solar cells, and ultra-violet photodetectors. However, the relatively lowelectron mobility of In203 NWs grown by chemical vapor deposition （CVD） haslimited their further utilization. In this study, utilizing in-situ Ga alloying,highly crystalline, uniform, and thin In2xGa2-2xO3 NWs with diameters down to30 nm were successfully prepared via ambient-pressure CVD. Introducing anoptimal amount of Ga （10 at.%） into the In2O3 lattice was found to effectivelyenhance the crystal quality and reduce the number of oxygen vacancies in theNWs. A further increase in the Ga concentration adversely induced the formationof a resistive β-Ga203 phase, thereby deteriorating the electrical properties ofthe NWs. Importantly, when configured into global back-gated NW field-effecttransistors, the optimized Inl.8Ga0.2O3 NWs exhibit significantly enhanced electronmobility reaching up to 750 cm2.V-l.s^-1 as compared with that of the pure In203NW, which can be attributed to the reduction in the number of oxygen vacanciesand ionized impurity scattering centers. Highly ordered NW parallel arrayeddevices were also fabricated to demonstrate the versatility and potency of theseNWs for next-generation, large-scale, and high-performance nanoelectronics,sensors, etc.
基金supported by the National Natural Science Foundation of China (Grant Nos.61378028,61475030,61421002,and 61377037)the National Basic Research Program of China (2012CB315701)the NCET Program (Grant No.NCET-13-0092)
文摘We report an erbium-doped fiber laser passively Q-switched by a few-layer molybdenum disulfide（MoS2） saturable absorber（SA）.The few-layer MoS2 is grown by the chemical vapor deposition method and transferred onto the end-face of a fiber connector to form a fiber-compatible MoS2 SA.The laser cavity is constructed by using a three-port optical circulator and a fiber Bragg grating（FBG） as the two end-mirrors.Stable Q-switched pulses are obtained with a pulse duration of 1.92 μs at 1560.5 nm.By increasing the pump power from 42 to 204 mW,the pulse repetition rate can be widely changed from 28.6 to 114.8 kHz.Passive Q-switching operations with discrete lasing wavelengths ranging from 1529.8 to 1570.1 nm are also investigated by using FBGs with different central wavelengths.This work demonstrates that few-layer MoS2 can serve as a promising SA for wideband-tunable Q-switching laser operation.
基金supported by the National Natural Science Foundation of China (No.51672229)the General Research Fund (CityU 11211317)+1 种基金the Theme-based Research (T42-103/16-N) of the Research Grants Council of Hong Kong SAR, China, and the Science Technology and Innovation Committee of Shenzhen Municipality (NO.JCYJ20170818095520778)a grant from the Shenzhen Research Institute, City University of Hong Kong.
文摘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.
基金This research was financially supported the National Natural Science Foundation of China(Nos.51672229,61605024,and 61775031)Fundamental Research Funds for the Central Universities(No.ZYGX2018J056)+2 种基金UESTC Foundation for the Academic Newcomers Award,the General Research Fund(CityU No.11275916)the Theme-based Research(No.T42-103/16-N)of the Research Grants Council of Hong Kong,Chinathe Science Technology and Innovation Committee of Shenzhen Municipality(No.Grant JCYJ20170818095520778).
文摘Due to the ultra-thin nature and moderate carrier mobility,semiconducting two-dimensional(2D)materials have attracted extensive attention for next-generation electronics.However,the gate bias stress instability and hysteresis are always observed in these 2D materials-based transistors that significantly degrade their reliability for practical applications.Herein,the origin of gate bias stress instability and hysteresis for chemical vapor deposited monolayer WS2 transistors are investigated carefully.The transistor performance is found to be strongly affected by the gate bias stress time,sweeping rate and range,and temperature.Based on the systematical study and complementary analysis,charge trapping is determined to be the major contribution for these observed phenomena.Importantly,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 data.All these results do not only indicate the validity of the charge trapping model,but also confirm the hysteresis being indeed caused by charge trapping.Evidently,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.
基金National Natural Science Foundation of China,Grant/Award Numbers:61975024,62074024Natural Science Foundation of Sichuan Province,Grant/Award Number:2022NSFSC0042Sichuan Science and Technology Program,Grant/Award Numbers:2023NSFSC0365,2023YFH0090。
文摘Two-dimensional transition metal dichalcogenides(TMDs)are needed in highperformance piezoresistive sensors due to their strong strain-induced bandgap modification and thereby large gauge factors.However,integrating a conventional high-temperature chemical vapor deposition(CVD)-grown TMD with a flexible substrate necessitates a transfer process that inevitably degrades the sensing properties of the TMDs and increases the overall fabrication complexity.We present a high-performance piezoresistive strain sensor that employs largearea PdSe_(2) films grown directly on polyimide(PI)substrates via plasma-assisted selenization of a sputtered Pd film.The reliable strain transfer from the substrate to the PdSe_(2) film ensures an outstanding strain-sensing capability of the sensor.Specifically,the sensors have a gauge factor of up to315±2.1,a response time under 25 ms,a detection limit of 8×10^(-6),and an exceptional stability of over 104 loadingunloading cycles.By attaching the sensors to the skin surface,we demonstrate their application for measuring physiological parameters in health care monitoring,including motion,voice,and arterial pulse vibration.Furthermore,using the PdSe_(2) film sensor combined with deep learning technology,we achieved intelligent recognition of artery temperature from arterial pulse signals with only a 2%difference between predicted and actual temperatures.The excellent sensing performance,together with the advantages of low-temperature fabrication and simple device structure,make the PdSe_(2) film sensor promising for wearable electronics and health care sensing systems.
