垂直靶向脉冲激光沉积制备ZnO纳米薄膜

用一种新颖的制备纳米粒子与薄膜的垂直靶向脉冲激光沉积(VTPLD)方法,在室温及空气气氛下,于玻璃基底上成功地制备出ZnO纳米薄膜.用扫描电子显微镜(SEM)和X射线衍射(XRD)仪对ZnO纳米薄膜的表面形貌和结构进行了表征,用荧光光谱仪对薄膜的光致发光(PL)性能进行了测量.结果表明,当激光功率为13 W时,沉积出的粒子大小较均匀,尺寸在40 nm左右,且粒子排列呈现出一定方向性;当激光功率为21 W时,沉积的ZnO纳米薄膜图呈现出微纳米孔的连续薄膜.在玻璃基底上沉积的ZnO纳米薄膜有一主峰对应的(002)衍射晶面,表明ZnO纳米薄膜具有良好的c轴取向性.不同激光功率下沉积ZnO纳米薄膜经500 ℃热处理后的PL峰,其强度随激光能量而变化,最大发光波长位于412 nm.     

射频磁控溅射制备非晶WO3薄膜的结构及其光电性质研究

采用射频磁控溅射技术,以WO3陶瓷靶为原料,在透明导电氧化铟锡（ITO）玻璃上沉积了非晶相WO3薄膜,研究了溅射功率对薄膜结构及光学性质的影响,并研究了WO3薄膜的电致变色特性。利用扫描电子显微镜（SEM）、X射线衍射技术（XRD）表征了薄膜的表面形貌和内部结构;利用UV-Vis分光光度计表征了薄膜在变色前后的光学透过性质,利用电化学测试工作站研究了WO3薄膜的电致变色性质,并从原理上分析了WO3薄膜的变色机理。研究结果表明,不同功率下获得的WO3薄膜均为非晶结构,在可见光范围内有较高的透过率。透明的WO3薄膜在负向电压下逐渐转变成深蓝色,且在撤去电压后其颜色不变,当施加正向电压时,薄膜又转换为透明态,表现出良好的电致变色特性。所制备WO3薄膜在550nm处褪色态的透过率为83%,着色态的透过率为29%,使得该薄膜在智能窗方面具有广阔的应用前景。     

工艺参数对WO_x薄膜电致变色特性和结构的影响

采用直流反应磁控溅射工艺,以纯钨靶为靶材在铟锡氧化物玻璃上制备电致变色WOx薄膜,研究了氧含量、溅射功率及溅射环境温度等工艺条件对其电致变色特性和结构的影响。实验结果表明:磁控溅射得到的WOx薄膜主要是非晶态的,在一定范围内,较低的氧含量,较高的溅射功率,较高的溅射环境温度下制备的WOx薄膜有较好的电致变色特性。     

聚苯胺/三氧化钨复合薄膜的制备与性质

采用溶胶-凝胶法在氧化铟锡(ITO)玻璃上制备三氧化钨(WO3)薄膜,将其在300℃下焙烧2h,再通过电沉积法在表面生长聚苯胺(PANI)薄膜.采用电化学方法、光谱分析法及扫描电镜等测试手段对WO3薄膜、PANI薄膜及PANI/WO3复合膜进行表征,发现复合膜着色态与褪色态透过率差异显著,变色效率(CE)达到57.94 cm2/C,比PANI和WO3薄膜的CE值28.94和10.55 cm2/C分别提高了50％和82％.扫描电镜结果表明,PANI薄膜表面结构疏松,有无序的微孔;而复合膜的结构规整、微孔排列相对有序且表面形貌均匀.     

具有核壳结构材料的薄膜热敏电阻

分别采用巯基丙酸包覆的银(Ag/MPA)和十二胺包覆的硫化银(Ag2S/DDA)纳米粒子通过涂布和煅烧两步法在低温下获得了Ag2S-Ag核壳结构薄膜热敏电阻(NTCR)和Ag2S薄膜NTCR.使用扫描电子显微镜(SEM)对Ag2S-Ag核壳结构薄膜形貌进行了表征,使用X射线衍射光谱仪(XRD)与透射电子显微镜(TEM)对薄膜粒子组成、结晶度及结构进行了测试分析,研究了不同制备条件下的Ag2S-Ag核壳结构薄膜NTCR的热敏电阻系数(NTC)特性,根据ASTM D3359附着力测试标准分析了薄膜对基底的附着力.结果表明,所制备器件膜厚均匀且表面平整,器件的膜厚为1.64 μm,热敏系数B、零功率电阻温度系数αT和电子活化能Ea值分别为2 707 K,-32 234× 10-6K-1和5.533×10-3 eV,附着力测试评价达5A.与Ag2S薄膜NT-CR相比,Ag2S-Ag核壳结构薄膜NTCR具有更优的NTC特性,膜厚可控,具有高灵敏度及环境适应性.     

PLD法制备ITO导电薄膜及其性能

为了研制可用于高温环境下进行应变测量的应变层,采用脉冲激光沉积(PLD)法在陶瓷基底上制备了氧化铟锡(ITO)薄膜.研究了PLD法中不同基底温度对ITO薄膜显微结构、电学性能以及阻温特性的影响.采用X射线衍射仪(XRD)测试了薄膜的晶体结构,通过四点探针测量法测得薄膜的薄层电阻,采用场发射扫描电子显微镜(FESEM)对...     

磁约束微波等离子体化学气相沉积金刚石薄膜

采用国内研制的电子回旋共振化学气相沉积(ECRCVD)设备,在单晶硅衬底上沉积了金刚石薄膜。通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)和激光拉曼谱仪(RAM)的测试,证明所沉积的薄膜具有明确的金刚石特征。所采用的ECRCVD设备,具有低压沉积、大面积均匀和低温生长的优点。这种方法在合成金刚石光学膜、半导体膜以及其它薄膜方面,很有发展潜力。     

脉冲激光沉积Al/Ag掺杂功能梯度薄膜

为了寻找制备梯度金属薄膜的新方法和新工艺,采用脉冲准分子激光扫描沉积技术,在Si(100)单晶衬底上沉积了Al/Ag掺杂功能梯度薄膜,并采用SEM和XPS对制备的薄膜进行了微观分析。分析结果表明,运用合适的激光参数和辅助放电,在沉积温度300℃时,制备出了Al/Ag组分比近似为5:1的掺杂梯度薄膜。该实验方法说明,利用脉冲激光与金属掺杂靶相互作用沉积梯度金属薄膜是可行的。     

N/Al共掺ZnO透明导电薄膜的制备及光电性能研究

采用射频磁控溅射和退火处理方法在普通玻璃基底上制备了N、Al共掺的ZnO薄膜。利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、四探针电阻测试仪和紫外-可见光光谱及X射线光电子能谱(XPS)等测试手段,分析了溅射功率对薄膜表面形貌结构及光电性能的影响。研究结果表明:不同溅射功率下所制备的薄膜均为具有c轴择优取向的六角纤锌矿结构,在可见光范围内,平均透过率都超过了85%;在溅射功率为140W条件下,N、Al共掺的ZnO薄膜显示出p型导电特性。     

膜厚对ITO薄膜的电学与光学性质的影响

用射频磁控溅射法在玻璃衬底上制备不同薄膜厚度氧化铟锡(ITO)透明导电薄膜.利用X线衍射(XRD)、透射光谱、四探针法和扫描电子显微镜(SEM)分析薄膜厚度(沉积时间)对ITO薄膜的结晶取向情况、透过率、电导率和表面形貌的影响.试验结果表明,在适当的沉积时间(5 min)下制备的ITO薄膜具有良好的光学性能和电学性能,其方阻为17 Ω/□,在可见光区域内的平均透过率为84%.     

Li_2分子A~1Σ_u~+→X~1Σ_g~+LIF和b~3Ⅱ_u→X~1Σ_g~+CIF发射光谱研究

用632.8nm CW激光获得了Li_2分子A~1∑_u~+(v′=15,J′=2)→X~1∑_g~+(v″=1～13,J″=1,3)R、P支双线LIF光谱。同时用光谱分析及碰撞动力学研究识别出另一支单线序列光谱来自b~3Ⅱ_u(v_b=21,N_b=1)→X~1∑_g~+(v″=3～6,J″=1)CIF发射。     

一种针对超宽带标准的CMOS Gm-C低通滤波器

采用TSMC 0.18µm CMOS工艺实现了一种针对超宽带标准的264MHz低通滤波器。该4阶滤波器由两个二阶滤波器级联而成,相对于传统的二阶Gm-C滤波器设计,本文提出的二阶拓扑结构十分简单有效,节约了1个跨导单元,3个共模反馈网络,2个电容。因此芯片功耗和芯片面积大大降低,其他指标并无牺牲。测试表明该滤波器增益-0.5dB,频率响应实测结果与仿真吻合良好,芯片面积为〖0.06mm〗^2,远小于同类设计,在1.8V电源电压下,电流消耗为3mA。     

Photoluminescence characteristics of GaN/lnGaN/GaN quantum wells

Photoluminescence (PL) characteristics of GaN/lnGaN/GaN single quantum wells (QWs) and an InGaN/GaN single heterojunction were studied using continuous wave (CW) and pulsed photoluminescence in both edge and surface emitting configurations. Samples were grown on c-plane sapphire substrates by atmospheric pressure metalorganic chemical vapor deposition (MOCVD). Room temperature and 77K PL measurements were performed using a CW Ar-ion laser (305 nm) and a frequency tripled (280 nm), pulsed, mode-locked Ti: sapphire laser. CW PL emission spectra from the quantum wells (24, 30, 80Å) were all blue shifted with respect to the reference sample. The difference (i. e., the blue shift) between the measured value of peak emission energy from the QW and the band-edge emission from the reference sample was attributed to quantum size effects, and to strain arising due to a significant lattice mismatch between InGaN and GaN. In addition, stimulated emission was observed from an InGaN/GaN single heterojunction in the edge and surface emitting configu-ration at 77K. The narrowing of emission spectra, the nonlinear dependence of output emission intensity on input power density, and the observation of a strongly polarized output are presented.     

MOCVD生长Al0.48Ga0.52N/Al0.54Ga0.36N多量子阱的结构和光学特性

采用金属有机物化学气相淀积(MOCVD)技术,在蓝宝石衬底上生长了Al0.48Ga0.52N/Al0.54Ga0.36N多量子阱(MQWs)结构。通过双晶X射线衍射(DCXRD)、原子力显微镜(AFM)和阴极荧光(CL)等测试技术,分别对样品的结构和光学特性进行了表征。在DCXRD图谱中,可以观察到明显的MQWs衍射卫星峰,通过拟和,MQWs结构中阱和垒的厚度分别为2.1和9.4nm,Al组分分别为0.48和0.54。在AFM表面形貌图上,可以观察到清晰的台阶流,表明MQWs获得了二维生长;与此同时,MQWs结构存在一些裂缝,主要原因为AlGaNMQWs结构和下层GaN层间存在很大的应力。CL测试表明,AlGaNMQWs结构的发光波长为295nm,处于深紫外波段,同时观察到处于蓝光、绿光波段的缺陷发光。     

Metamaterial inspired quad band circularly polarized antenna for WLAN/ISM/Bluetooth/WiMAX and satellite communication applications

A CPW fed metamaterial inspired Quadband circularly polarized antenna is presented in this article. The proposed antenna consists of defected ground structure with a radiating stub, which is at opposite side of the feedline. A waveguide mode of analysis is carried out for split ring resonator (SRR) and complimentary split ring resonator (CSRR) to enhance the properties of metamaterials. The proposed antenna analysis is taken iteration wise and used FR-4 Material as the substrate material with Ɛ_r = 4.4 and analysed using ANSYS electromagnetic desktop. The designed antenna projecting the peak gain of 4.8 dB and it is working in the application bands of WLAN/ISM/Bluetooth at 2.4 GHz, 5.8 GHz and 3.35 WiMAX band, X-band downlink satellite communication system (7.25–7.75 GHz) and ITU band (8–8.5 GHz) with fractional bandwidth of about 70%. Proposed antenna exhibits circular polarization at 2.39–2.55 GHz, 3.05–3.1 GHz, 4–5 GHz and 6.3–6.64 GHz respectively. To know the signal integrity of the antenna, time domain analysis is carried out for identical antennas in two conditions (face to face and side by side) with the help of CST microwave studio. The designed antenna showing excellent correlation in measurements with respect to simulation results.     

Systematic Synthesis of Compressive VDTA-Based T-T Filter with Orthogonal Control of fo and Q

Based on sixteen nullor-mirror models of the voltage differencing transconductance amplifier (VDTA) and port admittance matrices of the tow-Thomas (T-T) filter with orthogonal control between the characteristic frequency (f_o) and figure of merit (Q), two different categories of the voltage-mode and transconductance-mode T-T filters are synthesized by the means of the nodal admittance matrix (NAM) expansion method. The category A filter that employs two compressive VDTAs and two grounded capacitors includes four structures, and the category B filter that uses two compressive VDTAs, two grounded capacitors, and one grounded resistor, also includes four structures. These circuits are suitable for integrated circuit manufacture, and their parameters f_o and Q can be orthogonally adjusted with varying the bias currents of VDTAs. After the paper and pencil test is completed, the computer analyses, including alternating current (AC), parameter sweep, Monte Carlo (MC), and noise analyses, are performed to support the synthesis approach.     

Contactless electroreflectance study of a GaAIAs/lnGaAs/ GaAs/GaAIAs step quantum well structure

Using contactless electroreflectance at 300 and 77K, we have studied the inter-subband transitions from a GaAlAs/InGaAs/GaAs/GaALAs step quantum well structure (small well inside a large well) consisting of two layers A (In_xGa_1−xAs) and B (GaAs) with widths L_A and L_B, respectively, bounded by two thick barrier regions of Ga_x Al_yAs. By comparison of the observed spectral features with an envelope function calculation, including the effects of strain, we have been able to characterize the potential profile of the structure, i.e., L_A, L_B, x, and y. There is very good agreement between experiment and the intended materials param-eters. Such configurations are of considerable importance since (a) they form the basis for pseudomorphic high electron mobility transistors, and (b) also have applications in optoelectronics due to their large Stark shifts.     

Annealing effect on the metal gate effective work function modulation for the Al/TiN/SiO2/p-Si structure

In this work, the thermal annealing effect on the metal gate effective work function (EWF) modulation for the Al/TiN/SiO₂/p-Si(1 0 0) structure was investigated. Compared with the sample of TiN/SiO₂/p-Si(1 0 0) structure, for the sample additionally capped with Al the flat band voltage has a very obvious shift as large as 0.54 V to the negative direction after forming gas annealing. It is also revealed that the thermal budget can effectively influence both the EWF of the gate electrode and the thickness of the gate dielectric layer when a post annealing at 600 °C with different soak times was applied to the samples with Al cap. Material characterization indicates that the diffusion of Al and the formation of Al oxide during annealing should be responsible for all the phenomena. The interface trap density Dit calculated from the high-frequency C-V and the laser-assisted high-frequency C-V curves show that the introduction of Al does not cause reliability problem in the Al/TiN/SiO₂/p-Si structure.     

60/102/204混合细胞自动机的可逆性分析

细胞自动机的理论研究主要包括细胞自动机的分析和综合两个方面,而细胞自动机的可逆性分析则是细胞自动机分析中的核心问题。60/102/204混合细胞自动机作为一类重要的细胞自动机,利用矩阵分析方法将其状态转移表示为矩阵方程,从而分析其可逆性、可逆细胞自动机的数目和可逆细胞自动机的构造。60/102/204混合细胞自动机可逆性分析对于其在密码学、通信和测试等领域的应用具有重要意义。     

InGaN/GaN LEDs with a Si-doped InGaN/GaN short-period superlattice tunneling contact layer

Nitride-based light-emitting diodes (LEDs) with Si-doped n⁺-In_0.23Ga_0.77N/GaN short-period superlattice (SPS) tunneling contact top layer were fabricated. It was found that although the measured specific-contact resistance is around 1 × 10⁻² Ω-cm² for samples with an SPS tunneling contact layer, the measured specific-contact resistance is around 1.5×10⁰ Ω-cm² for samples without an SPS tunneling contact layer. Furthermore, it was found that one could lower the LED-operation voltage from 3.75 V to 3.4 V by introducing the SPS structure. It was also found that the LED-operation voltage is almost independent of the CP₂Mg flow rate when we grow the underneath p-type GaN layer. The LED-output intensity was also found to be larger for samples with the SPS structure.