ZnO/Ag/ZnO多层结构薄膜的光电性质

通过磁控溅射方法生长了不同银层厚度的ZnO/Ag/ZnO多层结构的薄膜,并对其形貌、光吸收谱、光致发光和光响应特性进行了比较研究.结果表明ZnO薄膜中银薄层的加入使得光致发光的强度增强.银层厚度为6 nm样品制成的器件在350 nm处的光响应度为0.06 A/W,相对于ZnO薄膜提高了一个数量级.而当银层厚度达到15 ...     

S-25与地NewS-25光阴极光谱响应特性的研究

本文研究了S-25与NewS-25光阴极的光谱响应特性.在850～1000nm范围光谱响应的提高主要归因于阴极层较厚,具有较大的阴极结构参量和截止波长.这既体现了NewS-25光阴极的优越性,也代这表了多碱阴极的发展方向.     

基于能量转换原理的磁电层合材料低频磁电响应分析

提出了一种基于能量转换原理的磁致伸缩/压电层合材料低频磁电响应模型,并对不同层合结构的磁电响应特性进行了对比研究.该模型假定层合材料层间能量传递通过层间剪切力来实现,利用应力函数法分析了磁致伸缩层和压电层的应力与应变,求出了磁致伸缩层的应变能和存储磁场能以及压电层的应变能和电场能;利用Hamilton最小能量原理求出了层间剪切力的大小,获得了开路状态下层合材料的低频磁电响应模型.发现磁电电压系数与磁致伸缩材料的磁导率、泊松比、磁机耦合系数以及压电材料的泊松比、机电耦合系数等有关,并对这些参数的影响进行了分析.同时对两层和三层结构的层合材料磁电特性进行了对比研究,发现层合结构不同则获得的磁电系数公式不同,用相应的公式计算得到的误差才会最小.研究结果表明,本文的理论误差小于6.5%,与其他方法相比,本文的理论模型能更好地描述磁电层合材料的低频磁电响应特性.     

大面积单层二硫化钼的制备及其光电性能

过渡金属硫族化合物(TMDCs)材料具有优异的电学和光电性能,在下一代光电子器件中具有广阔的应用前景.然而,大面积均匀生长单层的TMDCs仍然具有相当大的挑战.本工作提出了一种简单而有效的利用化学气相沉积(CVD)制备大面积单层二硫化钼(MoS₂)的方法,并通过调整氧化物前驱体的比例,调整MoS₂单晶/薄膜生长.随后,利用叉指电极掩膜板制备出单层MoS₂薄膜光电探测器.最后,在405 nm激光激发下,不同电压和不同激光功率条件下均表现出高稳定和可重复的光电响应,响应时间可达毫秒(ms)量级.此外,该光电探测器实现了405—830 nm的可见光到近红外的宽光谱检测范围,光响应度(R)高达291.7 mA/W,光探测率(D^*)最高达1.629×10⁹ Jones.基于该CVD制备的单层MoS2薄膜光电探测器具有成本低、能大规模制备,且在可见光到近红外的宽光谱范围内具有良好的稳定性和重复性的优点,为未来电子和光电子器件的应用提供了更多的可能性.     

包覆燃料颗粒碳化硅层的Raman光谱研究

本文研究了球床高温气冷堆燃料元件中包覆颗粒碳化硅层的Raman光谱. 通过分析不同制备条件下的碳化硅层断面的Raman光谱的峰位、半高全宽与强度, 明确了包覆颗粒中碳化硅层的晶相特征、密度变化和剩余应力等物性.通过分析不同密度碳化硅层一级Raman峰的同步、异步二维相关谱, 发现其LO模较TO模对于密度变化的响应更敏感. 这些结论为研究球床高温气冷堆燃料元件包覆颗粒中碳化硅层的结构及其物性有指导意义.     

壳层纳米颗粒的光散射行为研究

本文主要研究了Au-Si球型壳层纳米颗粒在电磁波作用下的散射行为,并将其与实心Au球、空心Au球、实心Si球和空心Si球的光散射行为进行了对比。利用Mie散射理论计算得出Au-Si球型壳层纳米颗粒在外加电磁波作用下的各阶电响应和磁响应,观察壳层结构的几何参数对电偶和磁偶共振峰位置的影响,并进一步研究Au材料中的电偶响应与Si材料中的电偶(磁偶)响应之间的耦合关系,找到其中的耦合规律。通过对单个球型壳层纳米颗粒散射行为的研究,为利用该颗粒周期性排列制备具有特殊电磁性质的人工特异材料提供理论指导。     

ZnS/CdS复合窗口层对CdTe太阳能电池短波光谱响应的影响

采用磁控溅射法制备了ZnS/CdS复合窗口层,并将其应用于CdTe太阳能电池。对所制备薄膜的形貌和结构等进行了研究。测试了具有不同窗口层的CdTe太阳电池的量子效率和光Ⅰ-Ⅴ特性,分析了ZnS薄膜制备条件对CdTe电池器件性能影响;研究了CdS薄膜厚度和ZnS/CdS复合窗口层对短波区透过率以及CdTe太阳电池的光谱响应的影响。着重研究了具有ZnS/CdS复合窗口层的CdTe太阳电池的短波光谱响应。结果表明,CdS窗口层厚度从100 nm减至50 nm后,其对短波区光子透过率平均提高了18.3%,CdTe太阳电池短波区光谱响应平均提高了27.6%。衬底温度250 ℃条件下制备的ZnS晶粒尺寸小于室温下制备的ZnS。具有ZnS/CdS复合窗口层的CdTe电池中,采用衬底温度250 ℃沉积ZnS薄膜来制备窗口层的电池器件,其性能要优于室温下沉积ZnS制备窗口层的电池器件。这说明晶粒尺寸的大小对电子输运有一定影响。在相同厚度CdS的前提下,具有ZnS/CdS复合窗口层的CdTe电池比具有CdS窗口层在短波的光谱响应提高了约2%。这说明ZnS/CdS复合窗口层能够做到减少对短波光子的吸收,从而使更多的光子被CdTe电池的吸收层吸收。     

用MOCVD方法制备的n型GaN薄膜紫外光电导

报道了用MOCVD方法制备的非掺杂的和Mg弱掺杂的n型GaN薄膜的紫外光电导特性.结果表明这些n型样品具有显著的紫外光响应,而且光响应弛豫时间也较短.在弱光范围,光响应随光强的变小呈线性减弱,且光响应的弛豫时间变长.     

用MOCVD方法制备的n型GaN薄膜紫外光电导

报道了用MOCVD方法制备的非掺杂的和Mg弱掺杂的n型GaN薄膜的紫外光电导特性.结果表明这些n型样品具有显著的紫外光响应,而且光响应弛豫时间也较短.在弱光范围,光响应随光强的变小呈线性减弱,且光响应的弛豫时间变长.     

掺Yb双包层光纤放大器的瞬态增益和频率响应

在理论上和实验上对掺Yb双包层光纤放大器(YDCFA)的瞬态增益特性进行了研究.建立了简化的瞬态增益基本模型,数值计算了低频光脉冲经过双包层光纤的放大波形,分析了瞬态增益饱和和恢复特性.在实验中对种子源放大的YDCFA的脉冲特性进行了分析,证实了其瞬态增益的低频响应特性.     

不同绝缘层上生长的并五苯薄膜及其OTFT器件性能的研究

分别以SiO₂和PMMA为绝缘层材料制备了底栅顶接触结构的OTFT器件,得到以PMMA为绝缘层的器件具有更好的性能,其场效应迁移率为0.207 cm2·Vs-1,开关电流比为4.93×103,阈值电压为-4.3 V;而以SiO₂为绝缘层的器件,其场效应迁移率仅为0.039 cm2·Vs-1,开关电流比为5.98×102,阈值电压为-5.4 V。为分析器件性能差异的原因,测得了SiO₂和PMMA薄膜表面的AFM图谱及其上沉积并五苯薄膜后的AFM和XRD图谱。通过AFM图谱发现PMMA表面较SiO₂表面粗糙度小,其表面粗糙度的均方根值为0.216 nm,而二氧化硅薄膜表面粗糙度的均方根值为1.579 nm;且发现在PMMA上生长的并五苯薄膜的成膜质量优于在SiO₂,具有较大的晶粒尺寸和较少的晶粒间界。通过XRD图谱发现在PMMA上生长的并五苯薄膜具有明显的衍射峰,进一步证明了在PMMA上生长的并五苯薄膜具有更好的结晶状况,将更有利于载流子的传输。     

Laser forward transfer of silver electrodes for organic thin-film transistors

Organic thin-film transistors (OTFTs) with top- and bottom-contact configurations were fabricated using silver nano-inks printed by laser forward transfer for the gate and source/drain electrodes with pentacene and poly-4-vinylphenol as the organic semiconductor and dielectric layers, respectively. The volume of the laser-printed Ag pixels was typically in the subpicoliter (0.2–0.4 pl) range. The top-contact OTFTs resulted in lower contact resistance compared to those obtained from the bottom-contact OTFTs, and showed improved overall device performance. The top-contact OTFTs exhibited field-effect mobilities of ∼0.16 cm² V⁻¹ s⁻¹ and on/off current ratios of ∼10⁵.     

Organic insulator layer influence on the electrical properties of N,N’-di (2-ethylhexyl) - 3, 4, 9, 10-perylene diimide organic thin-film transistors: Experiment and modeling

In this work, n- type organic thin film transistors (OTFTs) based on different kinds of organic dielectrics were fabricated, characterized and theoretically investigated. Three kinds of organic insulators were applied as dielectric gate which are: divinyl tetramethyl disiloxane-bis (benzo-cyclobutene) (BCB), poly(vinylalcohol) (PVA) and poly (4-vinyl phenol) (PVP). Analytical model was applied to describe the electrical behavior of the fabricated OTFTs and to explain the absence of saturation of the drain current for the device based on PVA dielectric. In addition, Meyer–Neldel rule-grain boundary model was applied for the calculation of total resistance of OTFTs based on different dielectrics materials. The theoretical results of output characteristics and total resistance showed an excellent agreement with the experimental measurements. The experimental and theoretical calculations revealed that the n-channel OTFTs based on BCB as an insulator layer exhibited superior electrical characteristics in terms of threshold voltage, mobility and drain current compared with the devices based on PVA and PVP as a gate insulator layer. The device based on BCB organic insulator layer has the largest mobility of 4?×?10^?3 cm² V^?1 s^?1, the smallest leakage current relative to the devices based on PVA and PVP. While, the device fabricated with PVP organic insulator gate has a large trap density on the PVP-EHPDI interface which causes a pronounced decrease in field effect mobility and consequently drain current.     

Electrical Characterization of Copper Phthalocyanine Thin-Film Transistors with Fluoride Gate Insulator

Different fluoride materlals are used as gate dielectrics to fabricate copper phthalocyanine （CuPc） thin film transistors （OTFTs）. The fabricated devices exhibit good electrical characteristics and the mobility is found to be dependent on the gate voltage from 10^-3 to 10^-1 cm^2V^-1 s^-1. The observed noticeable electron injection at the drain electrode is of great significance in achieving ambipolar OTFTs, The same method for formation of organic semiconductors and gate dielectric films greatly simplifies the fabrication process. This provides a convenient way to produce high-performance OTFTs on a large scale and should be useful for integration in organic displays.     

Electrical characteristics of top contact pentacene organic thin film transistors with SiO<Subscript>2</Subscript> and poly(methyl methacrylate) as gate dielectrics

Organic thin film transistors (OTFTs) were fabricated using pentacene as the active layer with two different gate dielectrics, namely SiO₂ and poly(methyl methacrylate) (PMMA), in top contact geometry for comparative studies. OTFTs with SiO₂ as dielectric and gold deposited on the rough side of highly doped silicon (n⁺-Si) as gate electrode exhibited reasonable field effect mobilities. To deal with poor stability and large leakage currents between source/drain and gate electrodes in these devices, isolated OTFTs with reduced source/drain contact area were fabricated by selective deposition of pentacene on SiO₂/PMMA through shadow mask. This led to almost negligible leakage currents and no degradation in electrical performance even after 14 days of storage under ambient conditions. But, the field effect mobilities obtained were lower than 10⁻³ cm² V⁻¹ s⁻¹, whereas by using PMMA as gate dielectric with chromium deposited on the polished side of n⁺-Si as gate electrode, improved field effect mobilities (>0.02 cm² V⁻¹ s⁻¹) were obtained. PMMA-based OTFTs also exhibited lower leakage currents and reproducible output characteristics even after 30 days of storage under ambient conditions.      

Optimization and improvement of TIPS–pentacene transistors (OTFT) with UV–ozone and chemical treatments using an all-step solution process

We fabricated an organic thin-film transistor (OTFT) using an all-step solution process. The printed layers, in which the electrode (silver), dielectric layer (BaTiO₃–PMMA), source–drain layer, and semiconductor 6,13-Bis(triisopropylsilylethynyl)pentacene(TIPS–pentacene), were optimized using roll-to-roll, an inkjet printer, and drop-casting. After coating the source–drain layer, we applied ultraviolet (UV)–ozone and self-assembled monolayer (SAM) treatments to the composite layer. The OTFTs treated with the UV–ozone and SAM treatments were found to exhibit excellent performance and good properties in comparison to silicon-based OTFTs.     

Enhanced electrical properties of pentacene-based organic thin-film transistors by modifying the gate insulator surface

A reliable surface treatment for the pentacene/gate dielectric interface was developed to enhance the electrical transport properties of organic thin-film transistors (OTFTs). Plasma-polymerized fluorocarbon (CFx) film was deposited onto the SiO₂ gate dielectric prior to pentacene deposition, resulting in a dramatic increase of the field-effect mobility from 0.015 cm²/(V s) to 0.22 cm²/(V s), and a threshold voltage reduction from −14.0 V to −9.9 V. The observed carrier mobility increase by a factor of 10 in the resulting OTFTs is associated with various growth behaviors of polycrystalline pentacene thin films on different substrates, where a pronounced morphological change occurs in the first few molecular layers but the similar morphologies in the upper layers. The accompanying threshold voltage variation suggests that hole accumulation in the conduction channel-induced weak charge transfer between pentacene and CFx.     

Pulsed dielectric spectroscopy of supercooled liquids

Pulsed dielectric spectroscopy is introduced as a technique for selectively emphasizing specific components of the non-exponential dielectric response of matter. Samples studied include supercooled liquid propanol, propylene carbonate, and poly(lauryl-methacrylate). It is shown that particular sequences of pulses can be used to emphasize the fast response regime, to produce a cross-over or memory effect, or to eliminate the response of selected components. Furthermore, for materials characterized by broad distributions of relaxation times, the technique facilitates the investigation of a relatively narrow band from that distribution. It is also shown that the time domain spectroscopy can be combined with conventional frequency domain techniques to provide the characterization of dielectric response over an extraordinarily broad spectral range.     

Improved Performance by a Double-Insulator Layer in Organic Thin-Film Transistors

Organic thin film transistors based on pentacene are fabricated by the method of full evaporation. The thickness of insulator film can be controlled accurately, which influences the device operation voltage markedly. Compared to the devices with a single-insulator layer, the electric performance of devices by using a double-insulator as the gate dielectric has good improvement. It is found that the gate leakage current can be reduced over one order of magnitude, and the on-state current can be enhanced over one order of magnitude. The devices with double-insulator layer exhibit field-effect mobility as large as 0.14cm^2/Vs and near the zero threshold voltage. The results demonstrate that using a proper double insulator as the gate dielectrics is an effective method to fabricate OTFTs with high electrical performance.     

Organic thin-film transistors of pentacene films fabricated from a supersonic molecular beam source

Top-contact organic thin-film transistors (OTFTs) of pentacene have been fabricated on bare SiO₂ and SiO₂ modified with hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (OTS). The pentacene films were deposited from a supersonic molecular beam source with kinetic energy of incident molecules ranging from 1.5 to 6.7 eV. The field-effect mobility of OTFTs was found to increase systematically with increasing kinetic energy of the molecular beam. The improvements are more important on HMDS- and OTS-treated surfaces than on bare SiO₂. Tapping mode atomic force microscopy images reveal that pentacene thin films deposited at high kinetic energy form with significantly larger grains—independent of surface treatment—than films deposited using low-energy beams.