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Highly sensitive humidity sensors based on hexagonal boron nitride nanosheets for contactless sensing

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Nano Research 2023年第7期16卷 10279-10286页

作者： Hang Liu Jinxu Qin Xigui Yang Chaofan Lv Wentao Huang Fukui Li Chuang Zhang Yanran Wu Lin Dong Chongxin Shan Henan key laboratory of Diamond Optoelectronic materials and devices Key Laboratory of Materials PhysicsMinistry of EducationSchool of Physics&MicroelectronicsZhengzhou UniversityZhengzhou 450052China Institute of quantum materials and physics Henan Academy of SciencesZhengzhou 450046China

Humidity sensors with high sensitivity,rapid response,and facile fabrication process for contactless sensing applications have received considerable attention in recent ***,humidity sensors based on hexagonal boron nitride(h-BN)nanosheets that are synthesized by a facile ultrasonic process have been fabricated,which display an ultrahigh sensitivity of 28,384%at 85%relative humidity(RH),rapid response/recovery time(3.0/5.5 s),and long-term stability in a wide humidity detection range(11%-85%RH),superior to most of the reported humidity *** high sensitivity can be ascribed to the massive hydrophilic functional groups absorbed on the h-BN nanosheet *** from the high humidity sensing performances,contactless Morse code messaging and human writing and speech recognition have been *** work demonstrates the great potential of the high-performance h-BN nanosheet-based humidity sensors for future contactless sensing devices.

关键词： boron nitride humidity sensors contactless detection speech recognition

Fabry-Perot interference and piezo-phototronic effect enhanced flexible MoS_(2) photodetector

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Nano Research 2022年第5期15卷 4395-4402页

作者： Xuexia Chen Xun Yang Qing Lou Yuan Zhang Yancheng Chen Yacong Lu Lin Dong Chong-Xin Shan Henan key laboratory of Diamond Optoelectronic materials and devices Key Laboratory of Materials PhysicsMinistry of Educationand School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China

Flexible photodetectors(PDs)are indispensable components for next-generation wearable ***,two-dimensional(2D)materials have been implemented as functional flexible optoelectronic devices due to their characteristics of atomically thin layers,excellent flexibility,and strain *** this work,we developed a flexible photodetector based on MoS_(2)/NiO heterojunction,and Fabry-Perot(F-P)and piezo-phototronic effect have been employed to enhance the responsivity(R)and external quantum efficiency(EQE)of the *** F-P effect is utilized to improve the optical absorption of the MoS_(2),resulting in an enhancement in the photoluminescence(PL)of monolayer MoS_(2) and the EQE of the photodetector by 30 and 130 times,*** flexible photodetector exhibits an ultrahigh detectivity(D*)of 2.6×10^(14) Jones,which is the highest value ever reported for flexible MoS_(2) *** piezo-potential of monolayer MoS_(2) decreases the valence band offset at the interface of MoS_(2)/NiO,which increases the transfer efficiency of the photon-generated carriers *** 1.17%tensile strain,the R of the flexible photodetector can be enhanced by 271%.This research may provide a universal strategy for the design and performance optimization of 2D materials heterostructures for flexible optoelectronics.

关键词： flexible photodetector MoS_(2) Fabry-Perot(F-P)interference piezo-phototronic effect

Microwave damage susceptibility trend of a bipolar transistor as a function of frequency

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Chinese physics B 2012年第9期21卷 565-570页

作者：马振洋柴常春任兴荣杨银堂陈斌宋坤赵颖博 school of Microelectronics Xidian UniversityKey Lab of Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices

We conduct a theoretical study of the damage susceptibility trend of a typical bipolar transistor induced by a high-power microwave （HPM） as a function of frequency. The dependences of the burnout time and the damage power on the signal frequency are obtained. Studies of the internal damage process and the mechanism of the device are carried out from the variation analysis of the distribution of the electric field, current density, and temperature. The investigation shows that the burnout time linearly depends on the signal frequency. The current density and the electric field at the damage position decrease with increasing frequency. Meanwhile, the temperature elevation occurs in the area between the p-n junction and the n n＋ interface due to the increase of the electric field. Adopting the data analysis software, the relationship between the damage power and frequency is obtained. Moreover, the thickness of the substrate has a significant effect on the burnout time.

关键词： bipolar transistor high-power microwave frequency

Reverse blocking characteristics and mechanisms in Schottky-drain AlGaN/GaN HEMT with a drain field plate and floating field plates

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Chinese physics B 2016年第1期25卷 777-782页

作者：毛维佘伟波杨翠张金风郑雪峰王冲郝跃 key lab of ministry of education for Wide Band-Gap Semiconductor materials and devices School of Microelectronics Xidian University school of physics and Optoelectronic Engineering Xidian University

In this paper, a novel A1GaN/GaN HEMT with a Schottky drain and a compound field plate （SD-CFP HEMT） is presented for the purpose of better reverse blocking capability. The compound field plate （CFP） consists of a drain field plate （DFP） and several floating field plates （FFPs）. The physical mechanisms of the CFP to improve the reverse breakdown voltage and to modulate the distributions of channel electric field and potential are investigated by two-dimensional numer- ical simulations with Silvaco-ATLAS. Compared with the HEMT with a Schottky drain （SD HEMT） and the HEMT with a Schottky drain and a DFP （SD-FP HEMT）, the superiorities of SD-CFP HEMT lie in the continuous improvement of the reverse breakdown voltage by increasing the number of FFPs and in the same fabrication procedure as the SD-FP HEMT. Two useful optimization laws for the SD-CFP HEMTs are found and extracted from simulation results. The relationship between the number of the FFPs and the reverse breakdown voltage as well as the FP efficiency in SD-CFP HEMTs are discussed. The results in this paper demonstrate a great potential of CFP for enhancing the reverse blocking ability in A1GaN/GaN HEMT and may be of great value and significance in the design and actual manufacture of SD-CFP HEMTs.

关键词： A1GaN/GaN HEMT drain field plate floating field plate reverse breakdown voltage

Double [5]carbohelicene: facile synthesis, chiroptical properties,isomerization study, and lasing application

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Science China Chemistry 2025年第01期 233-240页

作者： Peipei Liu Yantong Li Meng-Xiang Wu Hao Kang Xiao-Li Zhao Lin Xu Linlin Liu Xiaodong Li Junfeng Fang Zhiwei Fang Ya Cheng Hai-Bo Yang Huakang Yu Xueliang Shi State key laboratory of Petroleum Molecular & Process Engineering Shanghai Key Laboratory of Green Chemistry and Chemical ProcessesSchool of Chemistry and Molecular Engineering East China Normal University school of physics and Optoelectronics South China University of Technology Institute of Polymer Optoelectronic materials & devices State Key Laboratory of Luminescent Materials & Devices South China University of Technology school of physics and Electronic Science Engineering Research Center of Nanophotonics & Advanced Instrument Ministry of EducationEast China Normal University State key laboratory of Precision Spectroscopy School of Physics and Electronic Science East China Normal University

Double carbohelicenes have attracted considerable attention due to their aesthetic structures, distinct π-conjugation extension, inherent chirality, and intriguing optical and electronic properties. Herein, the concise de novo synthesis of a new double[5]carbohelicene 1 together with its chiroptical properties, isomerization process and lasing application is presented. 1 was synthesized by a simple protocol involving the formation of a 6,6′-bipentacene as the key intermediate. It is worth noting that1 existed as two diastereomers 1-PP/MM and 1-PM, which were successfully isolated and unambiguously confirmed by Xray crystallography. The optical resolution of the racemic 1-PP/MM was successfully achieved by chiral-phase highperformance liquid chromatography（HPLC）, and 1-PP and 1-MM were characterized by circular dichroism. Interestingly, it was found that 1-PP/MM could be completely isomerized to 1-PM upon heating, and the detailed thermodynamics and kinetics of the isomerization process were systematically investigated. 1-PM exhibited deep-red luminescence with emission maximum at 723 nm and fluorescence quantum yield as high as 32.95%. Consequently, we can showcase the lasing application of 1-PM by doping with epoxy resin to assemble a bottle microlaser spontaneously, which the lasing wavelength is 796.6 nm at a threshold of 0.8 m J cm-2. We believe that our studies, including the facile synthesis methodology, detailed isomerization studies, and lasing application, will shed some light on the design and synthesis of novel carbohelical systems with more functions.

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Rational design of diamond through microstructure engineering:From synthesis to applications

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Carbon Energy 2024年第7期6卷 94-122页

作者： Yalun Ku Wentao Huang Xing Li Li Wan Kuikui Zhang Longbin Yan Ying Guo Shaobo Cheng Chongxin Shan Henan key laboratory of Diamond Optoelectronic materials and devices Key Laboratory of Material PhysicsMinistry of EducationSchool of Physics and Laboratory of Zhongyuan LightZhengzhou UniversityZhengzhouChina Institute of quantum materials and physics Henan Academy of SciencesZhengzhouChina

Diamond possesses excellent thermal conductivity and tunable ***,the high-pressure,high-temperature,and chemical vapor deposition methods are the most promising strategies for the commercial-scale production of synthetic *** diamond has been extensively employed in jewelry and cutting/grinding tasks,the realization of its high-end applications through microstructure engineering has long been ***,we discuss the microstructures encountered in diamond and further concentrate on cutting-edge investigations utilizing electron microscopy techniques to illuminate the transition mechanism between graphite and diamond during the synthesis and device *** impacts of distinct microstructures on the electrical applications of diamond,especially the photoelectrical,electrical,and thermal properties,are *** recently reported elastic and plastic deformations revealed through in situ microscopy techniques are also ***,the limitations,perspectives,and corresponding solutions are proposed.

关键词： diamond in situ microscopy microstructures phase transition structure-property relationship

Development and characteristic analysis of a field-plated Al_2O_3 /AlInN/GaN MOS-HEMT

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Chinese physics B 2011年第1期20卷 8-12页

作者：毛维杨翠郝跃张进成刘红侠毕志伟许晟瑞薛军帅马晓华王冲杨林安张金风匡贤伟 key lab of the ministry of education for Wide Band-Gap Semiconductor materials and devices School of MicroelectronicsXidian University school of Technical physics Xidian University

We present an AIInN/AlN/GaN MOS-HEMT with a 3 nm ultra-thin atomic layer deposition （ALD） Al2O3 dielectric layer and a 0.3 μm field-plate （FP）-MOS-HEMT. Compared with a conventional AIInN/AlN/GaN HEMT （HEMT） with the same dimensions, a FP-MOS-HEMT with a 0.6 μm gate length exhibits an improved maximum drain current of 1141 mA/mm, an improved peak extrinsic transconductance of 325 mS/mm and effective suppression of gate leakage in both the reverse direction （by about one order of magnitude） and the forward direction （by more than two orders of magnitude）. Moreover, the peak extrinsic transconductance of the FP-MOS-HEMT is slightly larger than that of the HEMT, indicating an exciting improvement of transconductance performance. The sharp transition from depletion to accumulation in the capacitance-voltage （C-V） curve of the FP-MOS-HEMT demonstrates a high-quality interface of Al2O3/AlInN. In addition, a large off-state breakdown voltage of 133 V, a high field-plate efficiency of 170V/#m and a negligible double-pulse current collapse is achieved in the FP-MOS-HEMT. This is attributed to the adoption of an ultra-thin Al2O3 gate dielectric and also of a field-plate on the dielectric of an appropriate thickness. The results show a great potential application of the ultra-thin ALD-Al2O3 FP-MOS-HEMT to deliver high currents and power densities in high power microwave technologies.

关键词： field-plate ultra-thin Al2O3 gate dielectric FP-MOS-HEMT atomic layer deposited

High-electric-field-stress-induced degradation of SiN passivated AlGaN/GaN high electron mobility transistors

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Chinese physics B 2009年第4期18卷 1601-1608页

作者：谷文萍段焕涛倪金玉郝跃张进城冯倩马晓华 school of Microelectronics Xidian University China key lab of ministry of education for Wide Band-Gap Semiconductor materials and devices

AlGaN/GaN high electron mobility transistors （HEMTs） are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current IDsat, maximal transconductance gm, and the positive shift of threshold voltage VTH at high drain-source voltage VDS. The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEC depletion a little during the high-electric-field stress. After the hot carrier stress with VDS = 20 V and VGS= 0 V applied to the device for 104 sec, the SiN passivation decreases the stress-induced degradation of IDsat from 36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of IDsat, which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted.

关键词： AlGaN/GaN high electron mobility transistors surface states traps in AlGaN passivation

A new physics-based self-heating effect model for 4H-SiC MESFETs

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Chinese physics B 2008年第12期17卷 4622-4626页

作者：曹全君张义门张玉明 key lab of education ministry for Wide Band-Gap Semiconductor materials and devices School of Microelectronics Xidian University

A new self-heating effect model for 4H-SiC MESFETs is proposed based on a combination of an analytical and a computer aided design （CAD） oriented drain current model. The circuit oriented expressions of 4H-SiC low-field electron mobility and incomplete ionization rate, which are related to temperature, are presented in this model, which are used to estimate the self-heating effect of 4H-SiC MESFETs. The verification of the present model is made, and the good agreement between simulated results and measured data of DC I - V curves with the self-heating effect is obtained.

关键词： 4H silicon carbide metal semiconductor field effect transistor self-heating effect com puter aided design