基于LabVIEW的低温半导体器件温度循环系统

为研究低温半导体器件如HgCdTe中长波红外探测器温度循环过程的失效机理,提出了一种基于LabVIEW的温度循环实验设备。LabVIEW既用于测试又用于步进电机等的控制,结构简单,运行高效。经过数千次温度循环实验表明,该设备运行比较稳定,能够满足对低温半导体器件的筛选要求。     

深低温工作甚长波面阵红外探测器封装技术

基于甚长波红外探测器对低于液氮温度工作环境的需求,提出了一种深低温工作甚长波红外探测器封装技术。通过对杜瓦组件漏热和芯片电学引出结构的优化设计,可控制芯片在30 K低温工作时整个杜瓦组件的静态热耗为0.65 W,最冷端位置的静态热耗为0.3 W,与之适配的两级脉管制冷机冷量可以满足上述热耗需求。完成了探测器组件的封装测试。结果表明,在制冷机膨胀机热端空气冷却测试条件下,探测器芯片部分可达到35 K的温度;杜瓦的外轮廓小于Φ130 mm×180 mm。该项技术成果促进了深低温工作的甚长波面阵红外探测器封装技术的发展。     

电阻阵列辐射输出特性评估

电阻阵列是一种出射式动态红外场景投射器件,它通过控制流经电阻元的电流使电阻发热产生红外辐射,达到成像目的.由于非均匀性校正等需求,需要使用红外成像探测器测试单个电阻元的辐射特性.由于输入电流和输出红外辐射之间复杂的非线性关系,电阻阵列的辐射输出特性主要通过测试数据拟合来获取.基于典型的光学系统配置,给出了电阻元辐射亮度与探测器辐射照度之间的关系式,分析了光轴上及轴外电阻元辐射亮度的测试方法;通过对硅桥和悬浮薄膜电阻阵列电阻元的分析,给出了实际温度与等效黑体温度之间的对应关系,对电阻阵列辐射输出特性的测试具有一定的理论参考价值.     

碲镉汞红外探测器高低温循环特性研究

由于卫星长寿命的要求与机械制冷机有限寿命的矛盾,制冷机必须采用间歇式工作模式,因此星载碲镉汞红外探测器在太空中工作会经受从常温(20℃)到低温(-173℃以下)的成千上万次的温度循环,这给红外探测器带来了新的可靠性问题.本文介绍了自主研发的高低温循环试验系统,液氮致冷,温度循环范围为295K到100K.利用试验系统对两种型号的红外探测器组件进行了温度循环试验可靠性研究,测试和统计了循环试验前后的电阻、信号和噪声变化,针对具体试验结果做了分析和解释,为器件的工艺研发和改进提供了参考.     

光导PbS 焦平面探测器制备中负载电阻的选取

负载电阻分流方式通常用于消除光导PbS探测器的背景电流,其中各探测单元光敏元电阻与相对应负载的阻值可以相等,也可以成一固定比例。为研究不同负载电阻均可应用于光导PbS焦平面探测器,采用尺寸同为100 m 100 m 的光敏元、分别为100 m 100 m 和200 m 50 m 的负载研制了线列1128 光导PbS 红外焦平面探测器。利用红外焦平面测试系统对不同负载电阻制备的器件性能进行了测试与分析。研究表明,采用不同负载电阻均获得了性能正常的器件;在相同的光敏元工作参数下,器件的平均黑体响应率、平均黑体探测率基本一致,负载对其均无影响。研究结果验证了仅通过调节负载电阻即可使器件背景输出电平平坦化的可行性。     

碲镉汞红外探测器高低温循环特性研究

由于卫星长寿命的要求与机械制冷机有限寿命的矛盾，制冷机必须采用间歇式工作模式，因此星载碲镉汞红外探测器在太空中工作会经受从常温(20℃)到低温(-173℃以下)的成千上万次的温度循环，这给红外探测器带来了新的可靠性问题。本文介绍了自主研发的高低温循环试验系统，液氮致冷，温度循环范围为295K到100K。利用试验系统对两种型号的红外探测器组件进行了温度循环试验可靠性研究，测试和统计了循环试验前后的电阻、信号和噪声变化，针对具体试验结果做了分析和解释，为器件的工艺研发和改进提供了参考。     

碲镉汞红外探测器高低温循环特性研究

由于卫星长寿命的要求与机械制冷机有限寿命的矛盾，制冷机必须采用间歇式工作模式，因此星载碲镉汞红外探测器在太空中工作会经受从常温（20℃）到低温（-173℃以下）的成千上万次的温度循环，这给红外探测器带来了新的可靠性问题。本文介绍了自主研发的高低温循环试验系统，液氮致冷，温度循环范围为295K到100K。利用试验系统对两种型号的红外探测器组件进行了温度循环试验可靠性研究，测试和统计了循环试验前后的电阻、信号和噪声变化，针对具体试验结果做了分析和解释，为器件的工艺研发和改进提供了参考。     

多元红外光导探测器电子学串音研究

在多元红外探测器的应用中,串音是影响探测器性能的一个重要因素。其中,多元红外光导探测器的电子学串音主要由探测元间的接地电阻引起。通过对光导探测器工作电路的原理分析,得出多元红外光导探测器的电子学串音与探测元间接地电阻的阻值成正比,与偏置电阻的阻值成反比,且与原信号反相的结论,并设计了电子学串音测试原理电路进行了实验测试。测试结果验证了理论分析的正确性。通过理论推导和实验测试证明：在接地电阻一定时,通过提高偏置电阻来抑制电子学串音的方法是可行的。     

多元红外探测器元内均匀性扫描测试系统

针对多元红外探测器元内均匀性参数测试需求,研究开发了一套红外小光点扫描测试系统,主要由红外点光源汇聚成像光学系统、视觉辅助对准系统和精密六自由度扫描工作台以及数据采集与处理系统构成.该系统获得了高质量微米尺度的红外小光点,可精确实现小光点与探测器的感光面的对准,并自动完成多元红外探测器各个元元内均匀性的测试.针对某型号探测器的测试实验表明,该系统具有高的测试效率,较好的测量少度和稳定性.     

用于低温半导体器件筛选的新型温度循环设备

在某些情况下斯特林制冷机采用间歇式工作方式,以延长卫星在太空中的服务年限,因此由斯特林机致冷的低温半导体器件如HgCdTe中长波红外探测器会经受成千上万次从-173℃以下到常温的温度循环,这个过程可能会造成器件的失效.为了研究器件的失效机理和可靠性,帮助筛选器件,本文介绍了一种自制新型的温度循环实验设备,型号TCE-a.经过数千次温度循环,设备满足器件筛选实验要求.     

Image coding using dual-tree discrete wavelet transform

In this paper, we explore the application of 2-D dual-tree discrete wavelet transform (DDWT), which is a directional and redundant transform, for image coding. Three methods for sparsifying DDWT coefficients, i.e., matching pursuit, basis pursuit, and noise shaping, are compared. We found that noise shaping achieves the best nonlinear approximation efficiency with the lowest computational complexity. The interscale, intersubband, and intrasubband dependency among the DDWT coefficients are analyzed. Three subband coding methods, i.e., SPIHT, EBCOT, and TCE, are evaluated for coding DDWT coefficients. Experimental results show that TCE has the best performance. In spite of the redundancy of the transform, our DDWT _ TCE scheme outperforms JPEG2000 up to 0.70 dB at low bit rates and is comparable to JPEG2000 at high bit rates. The DDWT _TCE scheme also outperforms two other image coders that are based on directional filter banks. To further improve coding efficiency, we extend the DDWT to an anisotropic dual-tree discrete wavelet packets (ADDWP), which incorporates adaptive and anisotropic decomposition into DDWT. The ADDWP subbands are coded with TCE coder. Experimental results show that ADDWP _ TCE provides up to 1.47 dB improvement over the DDWT _TCE scheme, outperforming JPEG2000 up to 2.00 dB. Reconstructed images of our coding schemes are visually more appealing compared with DWT-based coding schemes thanks to the directionality of wavelets.     

Influence of TCE concentration in thermal oxidation on reliability of SiC MOS capacitors under Fowler–Nordheim electron injection

The effects of trichloroethylene (TCE) concentration in SiC thermal oxidation on the reliability of MOS capacitors under Fowler–Nordheim (FN) electron injection have been investigated. It is found that TCE thermal oxidation can enhance the resistance of the SiO₂/SiC interface against generation of interface states and oxide charges caused by FN electron injection, and the resistance increases with TCE ratio increasing from 0 to 0.1. As compared with the control sample based on dry-O₂ oxidation, the interface-state generation at 0.25 eV below the conduction-band edge is 5, 23, and 170 times smaller for samples with TCE ratio of 0.01, 0.05 and 0.1 respectively. In addition, the interface traps and oxide-charge traps of fresh samples decrease with increasing TCE ratio for the ratio less than 0.01, and then increase for larger ratio. It is proposed that the enhanced resistance against the stress is attributed to the gettering or dislodging of electrical and physical defects by the chlorine atoms incorporated in the oxide during the TCE oxidation.     

Transparent flexible plastic substrates for organic light-emitting devices

In this paper, we describe the properties of flexible plastic substrates with a transparent conducting electrode (TCE), which are important for organic light-emitting devices (OLEDs). Specifically, we have evaluated the TCE electrical resistivity, surface roughness, electrode patterning, optical transmission, and the substrate water vapor/oxygen transmission. We have studied the effect of ultraviolet (UV)-ozone treatment on the TCE surface by using contact angle measurements and x-ray photoelectron spectroscopy (XPS). A decrease in the advancing contact angle by 30–40° and an increase of oxygen content on the TCE surface by 10 at.% were observed after the UV-ozone treatment. These changes facilitate the polymer adhesion to the TCE surface and increase the TCE surface work function, respectively. A sheet resistance of 12–13 Ω/□, an optical transmission greater than 80% over the visible range, and a surface roughness of 1.4–2.2-nm RMS over 50×50 μm² have been obtained for the plastic substrates. These properties are adequate for OLED applications based on United States Display Consortium specifications. Finally, we have found that a combination of hydrogenated amorphous silicon-nitride and silicon-oxide layers deposited on one side of the substrate at low-temperature reduces the water vapor and oxygen transmission rates (TRs) to less than 10⁻⁵ g/cm²-day-atm and about 10⁻⁷ cc/cm²-day-atm, respectively.     

Performance Improvement of Carbon-Nanotube-Incorporated Transparent Conducting Anode Film for Organic Device Application

Carbon nanotubes (CNTs) were incorporated into indium tin oxide and polythiophene by mixing and then spin coating or screen printing to form the transparent conducting electrode (TCE). With only approximately 0.005%, by weight, of CNTs in the TCE, the sheet resistance was found to drop by about 25% to 40%, without any significant decrease in the transmittance. Organic light-emitting devices (OLEDs) were then fabricated using these composite TCEs as the anode. In comparison with a device without the CNTs, there was an increase in the current density for the same applied voltage, mainly due to the contribution of hole current. In addition, the mechanical strength was improved, as seen from bending test of the device.      

TCE浓度对热氧化制备6H-SiC MOS特性的影响

研究了新型SiCMOS电容的制备工艺。采用干O2+CHCCl3(TCE)热氧化方法生长6H-SiCMOS氧化层。研究了TCE浓度与SiC/SiO2界面态电荷密度和氧化层电荷密度和应力下平带电压漂移的关系,随着TCE浓度的增加,SiC/SiO2界面态电荷密度和氧化层电荷密度先减小后增大,应力下平带电压漂移减小,得出了最佳TCE:O2浓度比。     

表面处理对HfO_2栅介质MOS电容界面特性的影响

在溅射淀积HfO2栅介质之前,采用NO、N2O、O2+CHCCl3(TCE)进行表面预处理。结果表明,预处理能改善界面和近界面特性,减小界面层厚度,尤其是新颖的TCE+少量O2的表面处理工艺,能有效抑制界面层的生长,大大降低界面态密度,减小栅极漏电流。其机理在于TCE分解产生的Cl2和HCl能有效地钝化界面附近Si悬挂键和其它结构缺陷,并能去除离子污染。     

Tethered capsule endoscopy, a low-cost and high-performance alternative technology for the screening of esophageal cancer and Barrett's esophagus

Esophageal cancer is currently the fastest growing cancer in the United States. To help combat the recent rise in morbidity, our laboratory has developed a low-cost tethered capsule endoscope system (TCE) aimed at improving early detection of esophageal cancer. The TCE contains a resonant fiberoptic laser scanner (1.6 mm O.D.) which fits into 6.4-mm easy-to-swallow capsule at the distal tip. The tethered portion contains a single mode optical fiber multiplexed to three laser diodes at the proximal end. This design offers two main advantages over current endoscope technology. First, because of its small size, the TCE can be swallowed with minimal patient discomfort, thereby obviating sedation. Second, by imaging via directed laser light, the TCE is strategically positioned to employ several burgeoning laser-based diagnostic technologies, such as narrow-band, hyperspectral, and fluorescence imaging. It is believed that the combination of such imaging techniques with novel biomarkers of dysplasia will greatly assist in identifying precancerous conditions such as Barrett's esophagus (BE). As the probe is swallowed, the fiber scanner captures high resolution, wide-field color images of the gastroesophageal junction (500 lines at 0.05-mm resolution) currently at 15-Hz frame rate. Video images are recorded as the capsule is slowly retracted by its tether. Accompanying software generates panoramic images from the video output by mosaicing individual frames to aid in pattern recognition. This initial report describes the rationale for the unique TCE system design, results from preliminary testing in vitro and in vivo, and discussion on the merits of this new platform technology as a basis for developing a low-cost screening program for esophageal cancer.     

Reducible‐Shell‐Derived Pure‐Copper‐Nanowire Network and Its Application to Transparent Conducting Electrodes

The concept of using core Cu nanowires (CuNWs) that are conformally encapsulated by a reducible fugitive material for transparent conducting electrodes (TCEs) with high oxidation stability is presented. By the chemical reaction of an acid with surface oxide and hydroxide, a uniform surface shell layer is readily obtained on each CuNW upon adding lactic acid to the CuNW dispersion. The Cu lactate shell prevents the core CuNW from oxidizing during storage and film formation, enabling the core Cu nanowires to maintain their characteristic optoelectronic properties. Through simple thermal annealing under a nitrogen atmosphere, the Cu lactate shell is easily decomposed to expose the underlying pure Cu, providing an effective way to produce a pure‐CuNW‐network TCE with a sheet resistance of 19.8 Ω sq^?1 and an optical transmittance of 85.5% at 550 nm. The application of the CuNW‐based TCE to the transparent top electrode in organometallic halide perovskite solar cells is further demonstrated for the first time, yielding a power‐conversion efficiency 9.88% as compared to that of 13.39% for conventional perovskite solar cells with an indium–tin‐oxide electrode. This study proposes the high feasibility of these CuNWs as a vacuum‐free and noble‐metal‐free transparent‐window electrode in perovskite solar cells.     

Dc leakage currents in trichloroethylene oxides

Undoped silicon dioxide is compared to oxide in which trichloroethylene (TCE) was used during growth. The gate leakage currents in MOS transistors are examined. It is shown that a reduction in the leakage current occurs in TCE oxides. A novel measurement technique is employed to examine the gate leakage currents of the MOSFETs.     

Silver grid transparent conducting electrodes for organic light emitting diodes

Polymer organic light emitting diodes (OLEDs) were fabricated using thin silver hexagonal grids replacing indium tin oxide (ITO) as the transparent conducting electrodes (TCE). Previous literature has assumed that thick metal grids (several hundred nanometres thick) with a lower sheet resistance (<10 Ω/□) and a similar light transmission (>80%) compared to thinner grids would lead to OLEDs with better performance than when thinner metal grid lines are used. This assumption is critically examined using OLEDs on various metal grids with different thicknesses and studying their performances. The experimental results show that a 20 nm thick silver grid TCE resulted in more efficient OLEDs with higher luminance (10 cd/A and 1460 cd/m² at 6.5 V) than a 111 nm thick silver grid TCE (5 cd/A and 159 cd/m² at 6.5 V). Furthermore, the 20 nm thick silver grid OLED has a higher luminous efficiency than the ITO OLED (6 cd/A and 1540 cd/m² at 6.5 V) at low voltages. The data shows that thinner metal grid TCEs (about 20 nm) make the most efficient OLEDs, contrary to previous expectations.