Spatial light manipulation devices using nonlinear polymeric materials

An electrically addressed spatial light modulator with 5 × 5 pixels is designed using nonlinear polymeric materials. Resonator structure for the material is proposed to minimize the driving voltages. Side-chain polymer poly-orange tom-1 isophoronedisocyanate (r ₃₃ = 23 pm/V) is used as a material. A modulation efficiency of 4.7% has been realized with 5.1 V_rms applied voltage at a wavelength of 633 nm. Very fast modulation at over 10 MHz has been demonstrated.     

提升啁啾脉冲激光信噪比的扫描滤波方法

基于扫描滤波原理, 提出了一种新的用以提升啁啾脉冲激光信噪比(signal-to-noise, SNR)的光学扫描滤波方法. 针对内置电光晶体的Fabry-Perot标准具的扫描滤波方案, 定量分析了其扫描滤波谱特性, 详细讨论了Fabry-Perot标准具平行平板的镜面反射率和内置电光晶体类型对输出脉冲信噪比的影响, 并进一步探讨了控制电压变化对信噪比提升效果的影响. 结果表明, 扫描滤波器的透射窗口带宽越窄, 信噪比的提升效果越好; 为了保证输出效果, Fabry-Perot标准具平行平板反射率应大于0.9; 对于内置二次电光晶体钽铌酸钾晶体的Fabry-Perot标准具扫描滤波方案, 其外加电压较内置普通线性电光晶体的方案更低, 且更易于控制; 钽铌酸钾晶体构成组分的不同对滤波器效果的影响并不大, 而控制电压和信号光啁啾率的变化则会对滤波效果产生较大影响.     

The fabrication and characterization of 4H SiC power UMOSFETs

The fabrication of 4H-SiC vertical trench-gate metal-oxide-semiconductor field-effect transistors(UMOSFETs) is reported in this paper.The device has a 15-μm thick drift layer with 3×1015 cm-3 N-type doping concentration and a 3.1μm channel length.The measured on-state source-drain current density is 65.4 A/cm2 at Vg = 40 V and VDS = 15 V.The measured threshold voltage(Vth) is 5.5 V by linear extrapolation from the transfer characteristics.A specific on-resistance(Rsp-on) is 181 mΩ·cm2 at Vg = 40 V and a blocking voltage(BV) is 880 V(IDS = 100 μA@880V) at Vg = 0 V.     

Switching effects in composite films based on the conjugated polymer polyfluorene and ZnO nanoparticles

The S- and N-shaped current—voltage characteristics have been studied for composite films of the conjugated polymer polyfluorene and ZnO nanoparticles deposited onto Al and In₂O₃/SnO₂ electrodes with and without an intermediate sublayer of the conducting polymer PEDT/PSS. The differences in the current— voltage characteristics of the systems (the N- and S-types, respectively) are interpreted using the electro-thermal switching model, which takes into account the structural and electric properties of PEDT/PSS. The switching provides both alignment of polymer molecules and tunneling of charge carriers, which leads to an increase in conductivity. The current flow in this structure causes an increase in temperature of conducting channels; when the temperature reaches certain levels, the conductivity of the channels decreases because the alignment of polymer molecules is upset, which creates an N-shaped form of the current—voltage characteristics.     

Polaron and ion diffusion in a poly(3-hexylthiophene) thin-film transistor gated with polymer electrolyte dielectric

Electrolytes are finding applications as dielectric materials in low-voltage organic thin-film transistors (OTFT). The presence of mobile ions in these materials (polymer electrolytes or ion gels) gives rise to very high capacitance (>10 μF/cm²) and thus low transistor turn-on voltage. In order to establish fundamental limits in switching speeds of electrolyte gated OFETs, we carry out in situ optical spectroscopy measurement of a poly(3-hexylthiophene) (P3HT) OTFT gated with a LiClO₄:poly(ethyleneoxide) (PEO) dielectric. Based on spectroscopic signatures of molecular vibrations and polaron transitions, we quantitatively determine charge carrier concentration and diffusion constants. We find two distinctively different regions: at V _G≥−1.5 V, drift-diffusion (parallel to the semiconductor/dielectric interface) of hole-polarons in P3HT controls charging of the device; at V _G<−1.5 V, electrochemical doping of the entire P3HT film occurs and charging is controlled by drift/diffusion (perpendicular to the interface) of ClO₄ ⁻ counter ions into the polymer semiconductor.     

Effects of heavy-ion irradiation on the electrical properties of rf-sputtered HfO2 thin films for advanced CMOS devices

HfO₂-based metal-oxide semiconductor (MOS) capacitors were irradiated with high-energy ion beam to study the irradiation effects in these films. HfO₂ thin films deposited by radio frequency (rf)-sputtering were irradiated with 80 MeV O⁶⁺ ions. The samples were irradiated and characterized at room temperature. Devices were characterized via 1 MHz capacitance–voltage (C?V) measurements using the midgap method. The irradiation induced dispersion in accumulation and depletion regions with increasing fluence is observed. After irradiation, the midgap voltage shift (Δ V _mg) of?0.61 to?1.92 V, flat band voltage shift (Δ V _fb) of?0.48 to?2.88 V and threshold voltage shift (Δ V _th) of?0.966 to?1.96 V were observed. The change in interface trap charge and oxide trap charge densities after 80 MeV O⁶⁺ ions irradiation with fluences were determined from the midgap to flat band stretch out of C?V curves. The results are reported and explained in terms of changes in microstructure and dielectric properties of the HfO₂ thin films after irradiation.     

掺杂PEDOT ∶PSS对聚合物太阳能电池性能影响的研究

研究了掺杂后poly(3,4-ethylene dioxythiophene):poly(styrenesulphonic acid)(PEDOT ∶PSS)电导率的变化以及掺杂PEDOT ∶PSS薄膜对聚合物太阳能电池器件性能的影响. 实验发现,向PEDOT ∶PSS中掺入极性溶剂二甲基亚砜(DMSO)明显提高了薄膜的电导率,掺杂后的电导率最大值达到1.25 S/cm,比未掺杂时提高了3个数量级. 将掺杂的PEDOT ∶PSS薄膜作为缓冲层应用于聚合物电池 (ITO/PEDOT ∶PSS/P3HT ∶PCBM/LiF/Al) 中,发现高电导率的PEDOT ∶PSS降低了器件的串联电阻,增加了器件的短路电流,从而提高了器件的性能. 最好的聚合物太阳能电池在100 mW/cm²的光照下,开路电压(V_oc)为0.63 V,短路电流密度(J_sc)为11.09 mA·cm^-2,填充因子(FF)为63.7%,能量转换效率(η)达到4.45%. 关键词： PEDOT ∶PSS 电导率 聚合物太阳能电池 能量转换效率     

A high voltage silicon-on-insulator lateral insulated gate bipolar transistor with a reduced cell-pitch

A high voltage( 600 V) integrable silicon-on-insulator(SOI) trench-type lateral insulated gate bipolar transistor(LIGBT) with a reduced cell-pitch is proposed.The LIGBT features multiple trenches(MTs):two oxide trenches in the drift region and a trench gate extended to the buried oxide(BOX).Firstly,the oxide trenches enhance electric field strength because of the lower permittivity of oxide than that of Si.Secondly,oxide trenches bring in multi-directional depletion,leading to a reshaped electric field distribution and an enhanced reduced-surface electric-field(RESURF) effect.Both increase the breakdown voltage(BV).Thirdly,oxide trenches fold the drift region around the oxide trenches,leading to a reduced cell-pitch.Finally,the oxide trenches enhance the conductivity modulation,resulting in a high electron/hole concentration in the drift region as well as a low forward voltage drop(Von).The oxide trenches cause a low anode-cathode capacitance,which increases the switching speed and reduces the turn-off energy loss(Eoff).The MT SOI LIGBT exhibits a BV of 603 V at a small cell-pitch of 24 μm,a Von of 1.03 V at 100 A/cm-2,a turn-off time of 250 ns and Eoff of 4.1×10?3 mJ.The trench gate extended to BOX synchronously acts as dielectric isolation between high voltage LIGBT and low voltage circuits,simplifying the fabrication processes.     

低阈值极化电压玻璃光波导电光效应的研究

采用热极化技术对掺锗玻璃条形光波导进行极化,通过光纤连接 (单模) 的Mach Zehnder Interferometer 系统测量条形波导内诱导出的电光效应,系统地研究了大气环境下极化条件(极化温度、极化时间、极化电压)对电光效应的影响.结果表明:在最佳极化条件下(406℃、-2.4 kV、20 min),波导内的电光系数为r_TM=0.059±0.001 pm/V, r_TE=0.053±0.001 pm/V,且波导结构中存在一个较低的阈值极化电压(100 V)和阈值极化温度(80℃),此时在波导样品内仍能被激发出可观察的电光效应;实验还发现采用负极化诱导方式产生的电光系数较正极化提高15%左右.     

Optimizing Design for the Traveling Wave Electrodes in Low-Drive High-Speed Electro-Optic Polymer Modulators

Electro-optic (EO) polymer modulators are very promising in the realization of cost-effective and high-performance optical transmissions. In this article, general strategies and specific designs of the traveling wave electrodes in EO polymer modulators were presented to reduce the modulator drive power while maintaining a broadband response. The optimum device parameters and corresponding conditions were estimated using finite element method based on electrode design. In calculating the results, the comprehensive characteristics of polymer modulator with 1.21 V half-wave voltage and 91 GHz bandwidth was demonstrated with electro-optic interaction length is 20 mm, electro-optic coefficient is 55 pm/V, and operation wavelength is 1.319 μm. These results agree with the 0.8 V half-wave voltage and 30 mm electro-optic interaction length reported in Science. In the five designs presented, a hybrid electrode structure combining CPW and microstrip lines were advanced. The characteristics of this structure are like that of microstrip lines with a single-arm electrode on one arm of the waveguide, but it solves the problem of microstrip to coaxial line transition and corona polarization.     

铱金属配合物磷光材料掺杂聚合物体系的电致发光特性

通过对一种新型贵金属铱的配合物磷光材料(pbi)₂Ir(acac)与咔唑共聚物进行物理掺杂, 制备了结构为indium-tin oxide(ITO)/poly(N-vinylcarbazole)(PVK): (pbi)₂Ir(acac)(x)/2,9-dimethyl-4,7-diphenyl-1,10-phenan throline(BCP)(20nm)/8-Hydroxyquinoline aluminum(Alq₃)(10nm)/Mg:Ag的聚合物电致磷光器件,研究了磷光聚合物掺杂体系在低掺杂浓度时(0.1%和0.5%(质量百分数,全文同))的光致发光(PL)和电致发光(EL)特性. 结果表明, 该掺杂体系的PL光谱和EL光谱中均同时存在主体材料PVK与磷光客体(pbi)₂Ir(acac)的发光光谱, 但主客体的发射强度不同,推测该掺杂体系在电致发光条件下, 同时存在主体材料到客体的不完全的能量传递和载流子直接俘获过程. 磷光掺杂浓度为0.1%的器件在19V电压下实现了白光发射, 色坐标为(0.32, 0.38), 掺杂浓度为0.5%的器件在20.6V电压下的最大发光亮度为11827 cd·m^-2, 而在13.4V电压下的最大流明效率为4.13 cd·A^-1. 关键词： 有机电致发光器件 铱配合物磷光 聚合物掺杂     

微晶硅薄膜晶体管稳定性研究

对有源区处于结构过渡区的微晶硅底栅薄膜晶体管，测试其偏压衰退特性时，观察到一种“自恢复”的衰退现象.当栅和源漏同时施加10 V的偏压时，测试其源-漏电流随时间的变化，发现源-漏电流先衰减、而后又开始恢复上升的反常现象.而当采用栅压为10 V、源-漏之间施加零偏压的模式时，源-漏电流随时间呈先是几乎指数式下降、随之是衰退速度减缓的正常衰退趋势.就此现象进行了初步探讨. 关键词： 过渡区硅材料 微晶硅薄膜晶体管 稳定性 自恢复衰退     

Partial-SOI high voltage P-channel LDMOS with interface accumulation holes

A new partial SOI (silion-on-insulator) (PSOI) high voltage P-channel LDMOS (lateral double-diffused metal-oxide semiconductor) with an interface hole islands (HI) layer is proposed and its breakdown characteristics are investigated theoretically. A high concentration of charges accumulate on the interface, whose density changes with the negative drain voltage, which increase the electric field (E_I) in the dielectric buried oxide layer (BOX) and modulate the electric field in drift region . This results in the enhancement of the breakdown voltage (BV). The values of E_I and BV of an HI PSOI with a 2-μm thick SOI layer over a 1-μm thick buried layer are 580V/μm and -582 V, respectively, compared with 81.5 V/μm and -123 V of a conventional PSOI. Furthermore, the Si window also alleviates the self-heating effect (SHE). Moreover, in comparison with the conventional device, the proposed device exhibits low on-resistance.     

Polymer electrolyte based solid state redox supercapacitors with poly (3-methyl thiophene) and polypyrrole conducting polymer electrodes

Types I and II solid state redox supercapacitors have been constructed using polypyrrole (pPy) and poly (3-methyl thiophene) (pMeT) conducting polymer electrodes with lithium ion conducting polymer electrolyte poly(ethylene oxide) (PEO)-LiCF₃SO₃ plasticised with poly (ethylene glycol) (PEG). The performance of the capacitors has been characterised by a.c. impedance, linear sweep voltammetry, galvanostatic charge-discharge methods and long term cycling tests. The asymmetric type II capacitors with p-doped pPy and pMeT electrodes give a capacitance value ∼ 2 mF cm⁻² (equivalent to 18 Fg⁻¹ of the total mass of the electrodes) and can be charged up to the voltage of 1.7 V. The symmetric type 1 capacitors of the configuration pPy | polymer electrolyte | pPy and pMeT | polymer electrolyte | pMeT show comparable values of capacitance but they are limited to the working voltage of <1.0 V. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

MEH-PPV与TiO2共混体系太阳电池性能分析

以MEH-PPV(poly(2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylene vinylene)为电子给体材料(Donor,D), TiO₂纳米线为电子受体材料(Acceptor,A),制成了共混体系太阳电池. 从D/A材料共混体系的紫外可见吸收光谱(UV-vis)、光荧光谱(PL)、器件的电荷传输的光导J-V图等方面,分析了MEH-PPV∶TiO₂体系器件性能变化的原因. 得出了当在纯MEH-PP 关键词： 太阳电池 聚合物 性能     

增强型AlGaN/GaN高电子迁移率晶体管高温退火研究

深入研究了两种增强型AlGaN/GaN高电子迁移率晶体管(HEMT)高温退火前后的直流特性变化.槽栅增强型AlGaN/GaN HEMT在500 ℃ N₂中退火5 min后,阈值电压由0.12 V正向移动到0.57 V,器件Schottky反向栅漏电流减小一个数量级.F注入增强型AlGaN/GaN HEMT在 400 ℃ N₂中退火2 min后,器件阈值电压由0.23 V负向移动到-0.69 V,栅泄漏电流明显增大.槽栅增强型器件退火过程中Schottky有效势垒     

Novel high-voltage power device based on self-adaptive interface charge

This paper presents a novel high-voltage lateral double diffused metal--oxide semiconductor (LDMOS) with self-adaptive interface charge (SAC) layer and its physical model of the vertical interface electric field. The SAC can be self-adaptive to collect high concentration dynamic inversion holes, which effectively enhance the electric field of dielectric buried layer (E_I) and increase breakdown voltage (BV). The BV and E_I of SAC LDMOS increase to 612 V and 600 V/μm from 204 V and 90.7 V/μm of the conventional silicon-on-insulator, respectively. Moreover, enhancement factors of η which present the enhanced ability of interface charge on E_I are defined and analysed.     

Transverse laser induced thermoelectric voltage effect in tilted La0.5Sr0.5CoO3 thin films

The transverse laser induced thermoelectric voltage effect has been investigated in tilted La_0.5Sr_0.5CoO₃ thin films grown on vicinal cut LaAlO₃ (1 0 0) substrates when films are irradiated by pulse laser at room temperature. The detected voltage signals are demonstrated to originate from the transverse Seebeck effect as the linear dependence of voltage on tilted angle in the range of small tilted angle. The Seebeck coefficient anisotropy ΔS of 0.03 μV/K at room temperature is calculated and its distorted cubic structure is thought to be responsible for this. Films grown on a series of substrates with different tilted angles show the optimum angle of 19.8° for the maximum voltage. Film thickness dependence of voltage has also been studied.     

Low-voltage antimony-doped SnO2 nanowire transparent transistors gated by microporous SiO2-based proton conductors

A battery drivable low-voltage transparent lightly antimony（Sb）-doped SnO2 nanowire electric-double-layer （EDL） field-effect transistor （FET） is fabricated on an ITO glass substrate at room temperature. An ultralow operation voltage of 1 V is obtained on account of an untralarge specific gate capacitance （- 2.14 μF/cm2） directly bound up with mobile ions-induced EDL （sandwiched between the top and bottom electrodes） effect. The transparent FET shows excellent electric characteristics with a field-effect mobility of 54.43 cm2/V. s, current on/off ration of 2 × 104, and subthreshold gate voltage swing （S = dVgs/d（logIds）） of 140 mV/decade. The threshold voltage Yth （0.1 V） is estimated which indicates that the SnO2 namowire transistor operates in an n-type enhanced mode. Such a low-voltage transparent nanowire transistor gated by a microporous SiO2-based solid electrolyte is very promising for battery-powered portable nanoscale sensors.     

First-principles investigation of V2CSe2 MXene as a potential anode material for non-lithium metal ion batteries

The electrochemical performances of the V₂CSe₂ MXene as anode materials for Na, K, Mg, Ca, and Al-ion batteries have been systematically investigated by the first-principles method. The adsorption energies of metal atoms show that Na, K, and Ca atoms can effectively adsorb on the V₂CSe₂, except for Mg and Al atoms. The large diffusion constants for Na, K, and Ca atoms calculated by the diffusion energy barriers (0.098 eV for Na, 0.066 eV for Ca, and 0.24 eV for Ca) indicate the high mobility on the V₂CSe₂ surface. Significantly, the maximum theoretical capacities of V₂CSe₂ reach up to 394.12 mA h/g for Na and Ca ions. Furthermore, the low average open-circuit voltage (OCV) (0.150 V for Na, 0.175 V for K, and 0.072 V for Ca) indicates the V₂CSe₂ is a suitable anode material. These results provide fundamental guidance for the V₂CSe₂ monolayer as anode materials of non-lithium metal-ion batteries.