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Adiabatic cooling for cold polar molecules on a chip using a controllable high-efficiency electrostatic surface trap

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Chinese Physics B 2014年第12期23卷 148-154页

作者：李胜强许亮夏勇汪海玲印建平 State Key Laboratory of Precision Spectroscopy Department of Physics East China Normal University

We propose a controllable high-efficiency electrostatic surface trap for cold polar molecules on a chip by using two insulator-embedded charged rings and a grounded conductor plate. We calculate Stark energy structure pattern of ND3 molecules in an external electric field using the method of matrix diagonalization. We analyze how the voltages that are applied to the ring electrodes affect the depth of the efficient well and the controllability of the distance between the trap center and the surface of the chip. To obtain a better understanding, we simulate the dynamical loading and trapping processes of ND3 molecules in a ｜J, KM = ｜1,-1 state by using classical Monte–Carlo method. Our study shows that the loading efficiency of our trap can reach ～ 88%. Finally, we study the adiabatic cooling of cold molecules in our surface trap by linearly lowering the potential-well depth（i.e., lowering the trapping voltage）, and find that the temperature of the trapped ND3 molecules can be adiabatically cooled from 34.5 m K to ～ 5.8 m K when the trapping voltage is reduced from-35 k V to-3 k V.

关键词： controllable high-efficiency surface trap cold polar molecules

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Effects of Bi-dopant and co-catalysts upon hole surface trapping on La_(2)Ti_(2)O_(7) nanosheet photocatalysts in overall solar water splitting

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Nano Research 2022年第1期15卷 438-445页

作者： Xiaoyan Cai Liang Mao Mamoru Fujitsuka Tetsuro Majima Sujan Kasani Nianqiang Wu Junying Zhang School of Materials Science and Physics Jiangsu Province Engineering Laboratory of High Efficient Energy Storage Technology and EquipmentChina University of Mining and TechnologyXuzhou 221116China School of Physics Beihang UniversityBeijing 100191China The Institute of Scientific and Industrial Research(SANKEN) Osaka UniversityMihogaoka 8-1IbarakiOsaka 567-0047Japan Department of Mechanical and Aerospace Engineering West Virginia UniversityMorgantownWV 26506-6106USA Department of Chemical Engineering University of Massachusetts AmherstAmherstMA 01003-9303USA

Pristine and Bi-doped lanthanum titanium oxide(La_(2)Ti_(2)O_(7))nanosheets have been synthesized as photocatalysts for overall solar water splitting.The surface hole trap is a critical factor that limits the photocatalytic activity of pristine La_(2)Ti_(2)O_(7)-Deposition of cobalt phosphate(Co-Pi)and platinum(Pt)nanoparticles on La_(2)Ti_(2)O_(7) cannot remove the surface traps although they are essential for enabling the oxygen and hydrogen evolution reactions.It is interesting that doping bismuth(Bi)into La_(2)Ti_(2)O_(7) nanosheets has eliminated the surface traps due to surface enrichment of Bi.The Co-Pi/Bi-La_(2)Ti_(2)O_(7)/Pt nanosheets exhibit increasing photocatalytic activity toward overall water splitting with increasing the Bi-dopant level up to 5 at.%.Further increasing the Bi-dopant level leads to the formation of localized states above the valence band,leading to the lifetime reduction of photogenerated charge-carriers,and jeopardizing the photocatalytic activity.This work proposes an effective strategy to address the surface trapping and surface catalysis issues in the nanostructured metal oxide photocatalysts.

关键词： photocatalyst water splitting surface trap co-catalyst solar fuel

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In situ optical spectroscopic understanding of electrochemical passivation mechanism on sol–gel processed WO_(3) photoanodes

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Journal of Energy Chemistry 2022年第8期31卷 20-28,I0002页

作者： Jianyong Feng Xin Zhao Bowei Zhang Zhong Chen Zhaosheng Li Yizhong Huang Collaborative Innovation Center of Advanced Microstructures National Laboratory of Solid State MicrostructuresCollege of Engineering and Applied SciencesNanjing UniversityNanjing 210093JiangsuChina School of Materials Science and Engineering Nanyang Technological UniversitySingapore 639798Singapore

A prevailing understanding on electrochemical activation of photoelectrodes is that electrochemical treatment leads to increased charge carrier densities thereby improved photoelectrode performances.Contrary to this understanding,in this study enhanced photoactivity of WO_(3) photoanode upon electrochemical treatment is ascribed to an extraordinary mechanism of surface trap passivation.The associated mechanism is analyzed by in situ optical spectroscopy,using which the optical property changes of WO_(3) electrode during electrochemical treatment are monitored.The results suggest surface W^(5+)species,the origin of surface traps on WO_(3) photoanodes,are converted to W^(6+) ions by electrochemical treatment.This study demonstrates the particular ability of the electrochemical strategy to passivate surface traps of photoanodes,and also shows the advantages of in situ optical spectroscopy to investigate the real-time electronic structure variations of electrodes during electrochemical treatment.

关键词： In situ optical spectroscopy Electrochromism surface trap Solar water splitting Tungsten oxide Hydrogen

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Characteristics and optimization of 4H-SiC MESFET with a novel p-type spacer layer incorporated with a field-plate structure based on improved trap models

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Journal of Semiconductors 2011年第7期32卷 28-33页

作者：宋坤柴常春杨银堂贾护军张现军陈斌 Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices of the Ministry of Education School of MicroelectronicsXidian University

A novel structure of 4H-SiC MESFETs is proposed that focuses on surface trap suppression.Characteristics of the device have been investigated based on physical models for material properties and improved trap models.By comparing with the performance of the well-utilized buried-gate incorporated with a field-plate （BG-FP） structure,it is shown that the proposed structure improves device properties in comprehensive aspects. A p-type spacer layer introduced in the channel layer suppresses the surface trap effect and reduces the gate-drain capacitance（C_（gd）） under a large drain voltage.A p-type spacer layer incorporated with a field-plate improves the electric field distribution on the gate edge while the spacer layer induces less C_（gd） than a conventional FP.For microwave applications,4H-SiC MESFET for the proposed structure has a larger gate-lag ratio in the saturation region due to better surface trap isolation from the conductive channel.For high power applications,the proposed structure is able to endure higher operating voltage as well.The maximum saturation current density of 460 mA/mm is yielded.Also,the gate-lag ratio under a drain voltage of 20 V is close to 90%.In addition,5%and 17.8%improvements in f_T and f_（max） are obtained compared with a BG-FP MESFET in AC simulation,respectively.Parameters and dimensions of the proposed structure are optimized to make the best of the device for microwave applications and to provide a reference for device design.

关键词： 4H-SiC MESFET surface trap p-type spacer layer microwave application

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