2．0～5．0μm红外临边辐射光谱与垂直分布特征分析

基于先进的临边探测方式,利用成熟的辐射传输模式MODTRAN 4,对中红外2～5μm大气临边辐射的光谱特性和垂直分布特征进行模拟,并针对不同大气/气象条件以及太阳/探测器位置,对临边辐射垂直分布的敏感性进行了模拟和分析,给出了有意义的结果.     

2.O～5.0 μm红外临边辐射光谱与垂直分布特征分析

基于先进的临边探测方式,利用成熟的辐射传输模式MODTRAN 4,对中红外2～5 μm大气临边辐射的光谱特性和垂直分布特征进行模拟,并针对不同大气/气象条件以及太阳/探测器位置,对临边辐射垂直分布的敏感性进行了模拟和分析,给出了有意义的结果.     

基于非局域热平衡模式的临近空间目标背景临边对比度模型

对临近空间目标的空基/星载红外探测中的目标背景临边对比度问题进行物理建模,详细阐述对比度的定义和模型中的高层大气辐射问题.利用适于模拟高层大气辐射的非局域热平衡模式,结合探测器噪声假定,计算理想黑体目标的临边对比度并分析高层大气辐射特性对对比度的影响.模拟结果表明,在评估目标探测可行性时必须考虑探测器噪声的影响;在高层大气临边路径下水汽波段比大气窗区的可探测性更好,而目标本征辐射与大气临边吸收和背景辐射间的关系导致了对比度复杂的变化特征.     

空间目标临边探测背景红外成像建模与图像仿真

临边红外观测是对辐射强度较弱空间目标的一种有效探测方式,探测临边背景的红外辐射分布规律直接影响目标检测跟踪的效果。通过实测图像对临边背景辐射统计特征进行建模:临边背景辐射亮度在地平线垂直和水平方向具有不同的分布规律,垂直分布与视线切线高度相关,水平方向可近似为正态分布,变异系数取值集中于[0.01,0.05]。基于建模成果提出了一种临边背景红外图像快速仿真方法,实验结果表明仿真图像与实测图像具有较高的一致性,验证了成像模型和仿真方法的有效性。同时,快速仿真方法耗时仅为常规逐像元仿真方法的1/200,能够满足实时仿真的需求。研究结果可应用于红外相机设计和目标检测算法测试等领域。     

地球临边场景红外遥感成像仿真方法

地球临边场景仿真是卫星红外探测领域的关键组成部分,是空中高速目标远距离探测场景模拟的重要基础。临边观测下的地球表面近似于球面,传统的基于海洋三维形态并计算表面辐射特性的海洋红外图像仿真方法不适用。云层的厚度和高度对红外辐射传输特性的计算有重要影响,视云层为粒子团的处理方法会大大降低仿真的计算速度。因此,研究了海洋和云的红外辐射模型、地球-空间坐标系与红外相机坐标系的转换关系和大气传输模型,提出地球临边场景红外遥感成像仿真方法。根据场景组分的差异,分别建立海洋分布模型、多层云分布模型,并根据海洋和云层的红外辐射与反射特性,构建地球临边场景红外辐射模型。通过地球-空间坐标系与相机坐标系的转换关系,利用大气传输理论和传感器效应仿真,计算各观测角度的地球临边场景卫星遥感红外仿真图像。实验结果表明:仿真得到的红外图像画质清晰,符合地球临边场景红外辐射特性,其平均拉普拉斯算子和可达0.15,平均灰度梯度可达0.70。     

中高层大气CO2临边辐射院模拟与观测对比分析

利用更新的高层大气辐射传输软件(SHARC)中的非局域热平衡辐射传输模式模拟了SABER传感器观测的CO2 15m、4.3m宽带通道临边辐亮度,并与相应的SABER实测数据进行了对比分析。讨论了CO2 non-LTE辐射传输的一般特性;验证了SHARC的可靠性,确定了其适用范围。在一定的精度要求下,利用SHARC模式可以较准确地模拟所有中纬度大气条件的CO2 15m、4.3m带临边辐射特性。而若要更精确地模拟中高层大气CO2 non-LTE辐射特性并应用到极地夏季等极端大气条件下,在提高该高度大气参数精度的同时,改进模式的算法也是必要的。     

非平衡大气的临边辐射快速计算模型

针对目前的非局地热力学平衡(NLTE) 大气辐射传输模型计算速度慢的不足,引入了计算速度快、计算精度较高的带模式算法,并建立了大气的NLTE临边辐射快速计算模型。首先基于分子上下能级布居计算了大气振动温度廓线。然后依据大气的动力学温度、振动温度与配分函数计算了偏离系数和吸收截面因子。最后提出了半球累加方法解算NLTE临边辐射传输方程。计算分析了1976 U.S.大气模式下的大气振动温度与吸收截面因子廓线,并给出了典型切向高度时CO2 15 μm波段在白天的临边辐射亮度。通过基于逐线积分算法的SHARC模型,验证了本模型计算结果的正确性。本模型进行一次NLTE辐射计算仅需耗费数秒,且具有理想的光谱分辨率(1 cm-1)。     

中高层大气临边红外辐射的LTE与non-LTE模拟对比

利用战略高空辐亮度代码(Strategic high-altitude radiance code, SHARC) 和通用大气辐射传输代码 (Combined atmospheric radiative transfer, CART) 模拟分析中高层大气临边红外辐射的算法适用范围。 通过模拟结果的对比,初步验证了CART临边模式的有效性。模拟结果表明,在主要的红外波段上,至少45 km以 下的平流层区域内临边红外辐亮度的计算都可以采取局域热力学平衡模式(Local thermodynamics equilibrium, LTE);不同的红外波段在不同的大气条件下,需要采用非局域热力学平衡模式 (Non-local thermodynamics equilibrium, non-LTE)的高度不同,其中15 $\mu$m波段在至少80 km的切点 高度以下都可以使用LTE模式模拟,但是对于CO$_2$ 4.3 $\mu$m带主导的3$\sim$5 $\mu$m波段和O$_3$ 9.6 $\mu$m带 主导的8$\sim$12 $\mu$m波段,在中间层的多数区域内就必须采用non-LTE模式。     

大气超高光谱探测仪临边辐射计算的误差分析——四种大气成分的不确定性实验

利用RFM 模式, 模拟计算了大气红外超高光谱探测仪探测的辐射传输中四种主要大气成分( CO₂、O₃、H₂O 和 N₂O ) 由于吸收线位置、强度和宽度的不确定性导致临边辐射计算的误差。在统计HITRAN2016 数据库中分子吸 收线不确定代码的基础上, 确定辐射传输计算使用不确定代码不小于3 的不确定值。不同分子吸收线的不确定性对 不同高度临边辐射影响不同, 起主导作用的不确定因子也不同。同时还模拟计算了大气红外超高光谱探测仪4 个探 测波段综合多种分子的3 个不确定因子(位移、强度、宽度) 导致的临边辐射误差, 为光谱通道选择和大气参数反演 提供了数据基础。     

基于模拟红外辐射的海雾监测应用研究

由于长波红外及中波红外辐射受雾滴中水汽的影响明显,结合大气红外探测仪(Atmospheric Infrared Sounder, AIRS)的特征,利用快速辐射传输模式(Community Radiative Transfer Model, CRTM)分别模拟了两个波段的通道辐射信息。对下垫面辐射和模式上行辐射进行分析后发现：(1)为排除下垫面的干扰,将CRTM模式的底层上行辐射减去下垫面辐射,此时分离出的贴地面辐射值大小与海雾的强弱分布一致,因此可用于对海雾水平分布的监测。(2）模式上行辐射及其梯度随高度的变化反映了垂直方向上的海雾强度变化;通过对其进行分析可实现对海雾垂直结构的监测。(3）分别对中波红外和长波红外通道辐射进行模拟分析后发现,两者均可反映海雾的三维空间特性。     

Research on affine equivalence enumeration of the three families vectorial function

In recent years,Qu-Tan-Tan-Li function,Zha-Hu-Sun function and Tang-Carlet-Tang function have been proposed with differential uniformity 4 and many good cryptographic properties.the counting problem of affine equivalent to the three families cryptographic functions was investigated.By using some properties of finite fields,the upper and lower bound of the number of affine equivalent to the Zha-Hu-Sun function,and the upper bound of the number of affine equivalent to the Qu-Tan-Tan-Li function and Tang-Carlet-Tang function were computed,respectively.Moreover,a conjecture was given about the exact number of affine equivalent to the Zha-Hu-Sun function.Results show that there are at least$2^{53}{\left[{\displaystyle \prod _{i=1}^8(2^i-1)}\right]}^2$cryptographic functions of affine equivalent to the Zha-Hu-Sun function over finite field GF(2⁸),which can be chosen as S-boxes of block ciphers.     

Material modification of the patterned wafer during dry etching and strip determined by XPS

XPS analysis on single damascene (SD) patterned wafers was performed to study the modification of materials, especially the sidewall, during etching and strip. LKD-5109, MSQ-type materials (k≈2.2) were used as ILD, SiC/SiO₂ as top hard mask (HM), and SiC as bottom liner. The etching in Ar/CF₄/CH₂F₂/O₂ creates a CF_x polymer passivation layer on all patterned surfaces. The etched sidewall surface consists of two regions; a thin skin layer of CF_x polymer and CF-rich SiOC layer behind. An N₂/O₂ strip removes CF_x polymer and CF-rich layer efficiently (less than 1 at.% fluorine content). Instead of fluorine, CN-rich layers containing 11–20 at.% nitrogen were observed for all surfaces. After N₂/O₂ strip, the sidewall consists of two regions; a few nanometers of CN rich SiOC layer at the surface and several tens of nanometers of a C-depleted oxide type layer. N₂/H₂ strip provides a thinner C-depleting oxide type layer than either N₂/O₂ and CF₄/O₂ strips. However, the N₂/H₂ strip cannot eliminate fluorine contamination more than the N₂/O₂ strip.     

CH3NH3PbI3和CH3NH3MnI3的电子结构和光学性质研究

采用第一性原理计算,研究了有机金属卤化物钙钛矿CH₃NH₃PbI₃和CH₃NH₃MnI₃的电子结构、磁性和光吸收。CH₃NH₃PbI₃和CH₃NH₃MnI₃都是具有直接带隙半导体,CH₃NH₃MnI₃磁基态为G型反铁磁序(G-AFM)。CH₃NH₃MnI₃在G-AFM状态下的带隙值为1.668 eV;当系统处于FM态时,多数自旋通道的带隙为0.696 eV,少数自旋通道的带隙为2.148 eV。结果表明,具有FM态的CH₃NH₃MnI₃的光激发电子将迅速熔化局域磁序。最后计算了CH₃NH₃PbI₃和CH₃NH₃MnI₃的光学特性,结果表明具有铁磁态的CH₃NH₃MnI₃(FM)表现出较强的红外光吸收。     

Nickel-based contact metallization for SiGe MOSFETs: progress and challenges

The Ni-based self-aligned silicide process has attracted a rapidly growing interest for contact metallization in Si technology, as the device dimensions are scaled down into the sub-100 nm regime. Incorporation of Ge in the electrodes of a MOSFET, i.e. gate and source/drain, in order to further enhance device performance, has made the study of Ni–Si_1−xGe_x interactions a scientifically and technologically important issue. Among the different germanosilicides of Ni, NiSi_1−uGe_u (i.e. mono-germanosilicide, with u possibly different from x in the Si_1−xGe_x) is the most desirable phase due to its low specific resistivity of 12–25 μΩcm. The focus of the present work is placed on issues concerning the phase and morphology stability of NiSi_1−uGe_u on single-crystal and polycrystalline Si_1−xGe_x substrates. The related experimental data from our recent work are analysed with reference to two classics on the formation of silicides by d’Heurle [J. Mater. Res. 3 (1988) 167] and by d’Heurle and Gas [J. Mater. Res. 1 (1986) 205]. Influences of C and Pt on the stability of NiSi_1−uGe_u are also covered. The electrical properties of the NiSi_1−uGe_u–Si_1−xGe_x contact are discussed referring to our latest experimental results.     

Clarifying the atomic origin of electron killers in β-Ga2O3 from the first-principles study of electron capture rates

The emerging wide bandgap semiconductor \begin{document}$ \beta $\end{document}-Ga₂O₃ has attracted great interest due to its promising applications for high-power electronic devices and solar-blind ultraviolet photodetectors. Deep-level defects in \begin{document}$ \beta $\end{document}-Ga₂O₃ have been intensively studied towards improving device performance. Deep-level signatures E₁, E₂, and E₃ with energy positions of 0.55–0.63, 0.74–0.81, and 1.01–1.10 eV below the conduction band minimum have frequently been observed and extensively investigated, but their atomic origins are still under debate. In this work, we attempt to clarify these deep-level signatures from the comparison of theoretically predicted electron capture cross-sections of suggested candidates, Ti and Fe substituting Ga on a tetrahedral site (Ti_GaI and Fe_GaI) and an octahedral site (Ti_GaII and Fe_GaII), to experimentally measured results. The first-principles approach predicted electron capture cross-sections of Ti_GaI and Ti_GaII defects are 8.56 × 10^–14 and 2.97 × 10^–13 cm², in good agreement with the experimental values of E₁ and E₃ centers, respectively. We, therefore, confirmed that E₁ and E₃ centers are indeed associated with Ti_GaI and Ti_GaII defects, respectively. Whereas the predicted electron capture cross-sections of Fe_Ga defect are two orders of magnitude larger than the experimental value of the E₂, indicating E₂ may have other origins like C_Ga and Ga_i, rather than common believed Fe_Ga.     

Enhanced magnetic anisotropy and high hole mobility in magnetic semiconductor Ga1-x-yFexNiySb

(Ga,Fe)Sb is a promising magnetic semiconductor (MS) for spintronic applications because its Curie temperature (T_C) is above 300 K when the Fe concentration is higher than 20%. However, the anisotropy constant K_u of (Ga,Fe)Sb is below 7.6 × 10³ erg/cm³ when Fe concentration is lower than 30%, which is one order of magnitude lower than that of (Ga,Mn)As. To address this issue, we grew Ga_1-x-yFe_xNi_ySb films with almost the same x (≈24%) and different y to characterize their magnetic and electrical transport properties. We found that the magnetic anisotropy of Ga_0.76-yFe_0.24Ni_ySb can be enhanced by increasing y, in which K_u is negligible at y = 1.7% but increases to 3.8 × 10⁵ erg/cm³ at y = 6.1% (T_C = 354 K). In addition, the hole mobility (µ) of Ga_1-x-yFe_xNi_ySb reaches 31.3 cm²/(V∙s) at x = 23.7%, y = 1.7% (T_C = 319 K), which is much higher than the mobility of Ga_1-xFe_xSb at x = 25.2% (µ = 6.2 cm²/(V∙s)). Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of (Ga,Fe)Sb by using Ni co-doping.     

交换超立方网络的(t, k)故障诊断度研究

故障诊断是网络系统修复的一个重要环节,PMC诊断模型是一种简单、易于理解的故障诊断模型。通过对以交换超立方网 为拓扑模型的多处理器系统进行结构分析,给出了该网络系统的一般化的故障诊断方法——(t,k)诊断方法,证明了在PMC模型下交换超立方网络 是 可诊断的,且是条件 可诊断的。结果表明,交换超立方网的(t,k)诊断度 大于其传统诊断度s+1,条件(t,k)诊断度 大于其传统条件诊断度4s?3。这些结果为交换超立方网络的故障诊断提供了重要的理论依据。     

ZnSb/Ti3C2Tx MXene van der Waals heterojunction for flexible near-infrared photodetector arrays

Two-dimension (2D) van der Waals heterojunction holds essential promise in achieving high-performance flexible near-infrared (NIR) photodetector. Here, we report the successful fabrication of ZnSb/Ti₃C₂T_x MXene based flexible NIR photodetector array via a facile photolithography technology. The single ZnSb/Ti₃C₂T_x photodetector exhibited a high light-to-dark current ratio of 4.98, fast response/recovery time (2.5/1.3 s) and excellent stability due to the tight connection between 2D ZnSb nanoplates and 2D Ti₃C₂T_x MXene nanoflakes, and the formed 2D van der Waals heterojunction. Thin polyethylene terephthalate (PET) substrate enables the ZnSb/Ti₃C₂T_x photodetector withstand bending such that stable photoelectrical properties with non-obvious change were maintained over 5000 bending cycles. Moreover, the ZnSb/Ti₃C₂T_x photodetectors were integrated into a 26 × 5 device array, realizing a NIR image sensing application.     

High-performance junction field-effect transistor based on black phosphorus/β-Ga2O3 heterostructure

Black phosphorous (BP), an excellent two-dimensional (2D) monoelemental layered p-type semiconductor material with high carrier mobility and thickness-dependent tunable direct bandgap structure, has been widely applied in various devices. As the essential building blocks for modern electronic and optoelectronic devices, high quality PN junctions based on semiconductors have attracted widespread attention. Herein, we report a junction field-effect transistor (JFET) by integrating narrow-gap p-type BP and ultra-wide gap n-type β-Ga₂O₃ nanoflakes for the first time. BP and β-Ga₂O₃ form a vertical van der Waals (vdW) heterostructure by mechanically exfoliated method. The BP/β-Ga₂O₃ vdW heterostructure exhibits remarkable PN diode rectifying characteristics with a high rectifying ratio about 10⁷ and a low reverse current around pA. More interestingly, by using the BP as the gate and β-Ga₂O₃ as the channel, the BP/β-Ga₂O₃ JFET devices demonstrate excellent n-channel JFET characteristics with the on/off ratio as high as 10⁷, gate leakage current around as low as pA, maximum transconductance (g_m) up to 25.3 µS and saturation drain current (I_DSS) of 16.5 µA/µm. Moreover, it has a pinch-off voltage of –20 V and a minimum subthreshold swing of 260 mV/dec. These excellent n-channel JFET characteristics will expand the application of BP in future nanoelectronic devices.