高温超导微波器件在雷达接收机中的应用

高温超导微波器件具有极低损耗和极低噪声的优良特性。文中将低温前端与常规接收机前端进行了性能指标的对比，对超导微波器件主要是低温前端的应用进行分析。得出结论：超导器件的应用使得接收机的灵敏度与抗干扰性能等关键指标得到大幅度提高。     

高温超导/铁电薄膜可调谐微波器件应用研究简介

高温超导/铁电薄膜可调谐微波器件具有高可调率、低损耗的优势,在未来智能化通信系统中有良好的应用前景。本文简介了可调谐器件的研究意义和高温超导可调谐技术比较,综述了铁电薄膜可调谐器件的研究进展和代表性成果,总结了其中的关键技术问题并给出了建议。     

高温超导体厚膜及其在微波无源器件上的若干应用

系统论述了高温超导体厚膜的概念、制备方法,高温超导体厚膜的特性,介绍了高温超导体厚膜在微波无源器件上的若干应用。     

Josephson Plasmon Resonance in Tl2Ba2CaCu2O8 High-Temperature Superconductor Tunable Terahertz Metamaterials

The Josephson plasmon resonance (JPR) offers a valuable probe to investigate the superconductivity in layered cuprate superconductors. However, the coupling between free space radiation and JPR in high-temperature superconductor (HTS) film remains challenging because the excitation of JPR demands the c-axis oriented electric field. The subwavelength resonators in metamaterials can enhance the localized electric field, which can be utilized to resolve this difficulty. Here, a tunable terahertz (THz) metamaterial made from Tl₂Ba₂CaCu₂O₈ (Tl-2212) HTS film is developed. The spectral response of Tl-2212 metamaterial has a tunable property at temperatures up to 90 K. The resonant excitation of Josephson plasmon in the metamaterial is observed. Simulation results indicate that the scattering of subwavelength resonators can provide the component of the z-axis electric field for the resonant excitation. The coupling between JPR and resonance modes of metamaterials is observed and explained using coupled mode theory. The temperature dependence of JPR frequency shows accordance with the experimental results of the pure film. This work provides an avenue to excite the JPR and probe superconducting condensate in the layered superconductor. The development of Josephson plasmonic metamaterials may contribute to tunable and nonlinear THz devices.     

高温超导滤波器在现代移动通信中的应用

本文简单介绍我国主要的峰窝移动通信网络以及目前移动蜂窝通信系统中的一些问题，介绍了国外高温超导（HTS）滤波器子系统的发展及在移动通信中的应用。高温超导滤波器子系统具有陡峭的、接近于思想的频率响应特性，能很好地抑制带外信号的干扰；非常高的灵敏度，能扩展覆盖区域；非常好的选择性，能充分利用频率资源，扩充系统容量，改善服务质量；性能好、体积小等优点。     

Thin‐Film‐Based Integrated High‐Transition‐Temperature Superconductor Devices

Since the discovery of superconductivity at temperatures above the technologically promising liquid nitrogen temperatures, applications based on superconductors have expanded and are being put to commercial use. However, superconductivity at higher temperatures typically occurs in complex materials requiring stringent material and environmental constraints. Such restraints make the realization and integration of these materials with normal materials a nontrivial aspect. In this progress report, unique features of these superconductors in terms of their synthesis, physical properties determining interface electrical transport, and their applications are discussed. A detailed progress report on these applications with remarks on efforts taken to integrate these devices with traditional platforms and semiconducting materials is provided.     

High Power,Room Temperature Terahertz Emitters Based on Dopant Transitions in 6H-Silicon Carbide

Electrically pumped high power terahertz(THz) emitters that operated above room temperature in a pulse mode were fabricated from nitrogen-doped n-type 6H-SiC. The emission spectra had peaks centered on 5 THz and 12 THz(20 meV and 50 meV) that were attributed to radiative transitions of excitons bound to nitrogen donor impurities. Due to the relatively deep binding energies of the nitrogen donors, above 100 meV, and the high thermal conductivity of the SiC substrates, the THz output power and operating temperature were significantly higher than previous dopant based emitters.With peak applied currents of a few amperes, and a top surface area of 1 mm2, the device emitted up to 0.5 mW at liquid nitrogen temperature(77 K), and tens of microwatts up to 333 K. This result is the highest temperature of THz emission reported from impuritybased emitters.     

High Power,Room Temperature Terahertz Emitters Based on Dopant Transitions in 6H-Silicon Carbide

Electrically pumped high power terahertz (THz) emitters that operated above room temperature in a pulse mode were fabricated from nitrogen-doped n-type 6H-SiC. The emission spectra had peaks centered on 5 THz and 12 THz (20 meV and 50 meV) that were attributed to radiative transitions of excitons bound to nitrogen donor impurities. Due to the relatively deep binding energies of the nitrogen donors, above 100 meV, and the high thermal conductivity of the SiC substrates, the THz output power and operating temperature were significantly higher than previous dopant based emitters. With peak applied currents of a few amperes, and a top surface area of 1 mm2, the device emitted up to 0.5 mW at liquid nitrogen temperature (77 K), and tens of microwatts up to 333 K. This result is the highest temperature of THz emission reported from impuritybased emitters.     

宽温区高温MOS器件优化设计

全面介绍了27－300℃定温区高温MOs器件的优化设计考虑及用计算机模拟技术进行优化设计的方法。研究结果表明，选取代化的设计参数可使设计的MOs器件在27－300℃宽温区工作并获得最佳高温性能。     

Ultrasensitive Room‐Temperature Terahertz Direct Detection Based on a Bismuth Selenide Topological Insulator

Despite their huge application capabilities, millimeter‐ and terahertz‐wave photodetectors still face challenges in the detection scheme. Topological insulators (TIs) are predicted to be promising candidates for long‐wavelength photodetection, due to the presence of Dirac fermions in their topologically protected surface states. However, photodetection based on TIs is usually hindered by the large dark current, originating from the mixing of bulk states with topological surface states (TSSs) in most realistic samples of TIs. Here millimeter and terahertz detectors based on a subwavelength metal–TI–metal (MTM) heterostructure are demonstrated. The achieved photoresponse stems from the asymmetric scattering of TSS, driven by the localized surface plasmon‐induced terahertz field, which ultimately produces direct photocarriers beyond the interband limit. The device enables high responsivity in both the self‐powered and bias modes even at room temperature. The achieved responsivity is over 75 A/W, with response time shorter than 60 ms in the self‐powered mode. Remarkably, the responsivity increases by several orders of magnitude in the biased configuration, with the noise‐equivalent power (NEP) of 3.6 × 10^?13 W Hz^?1/2 and a detectivity of 2.17 × 10¹¹ cm Hz^?1/2 W^?1 at room temperature. The detection performances open a way toward realistic exploitation of TIs for large‐area, real‐time imaging within long‐wavelength optoelectronics.     

基于电热耦合模型的功率器件结温预测

结温预测对于功率器件的可靠性分析具有重要意义,基于此,提出了一种基于电热耦合模型的功率器件结温预测方法。首先通过Twin Builder软件建立了绝缘栅双极晶体管(IGBT)的行为模型,通过电路仿真的手段获取IGBT的平均功耗为324 W;然后将IGBT的功耗代入有限元仿真模型中得到了IGBT模块温度场分布,最高温度为99.58℃;最后搭建了IGBT模块结温测试平台,将仿真结果与实验数据进行对比,验证温度场计算模型的有效性;并实验对比了IGBT功耗分别为119 W和294 W下的最高结温,得到的温度场计算误差在10%以内,验证了IGBT有限元模型的有效性。     

高温氧化对SiC MOS器件栅氧可靠性的影响

SiC金属氧化物半导体(MOS)器件中SiO2栅氧化层的可靠性直接影响器件的功能.为了开发高可靠性的栅氧化层,将n型4H-SiC (0001)外延片分别在1 200,1 250,1 350,1 450和1 550℃5种温度下进行高温干氧氧化实验来制备SiO2栅氧化层.在室温下,对SiC MOS电容样品的栅氧化层进行零时击穿(TZDB)和与时间有关的击穿(TDDB)测试,并对不同干氧氧化温度处理下的栅氧化层样品分别进行了可靠性分析.结果发现,在1 250℃下进行高温干氧氧化时所得的击穿场强和击穿电荷最大,分别为11.21 MV/cm和5.5×10-4 C/cm2,势垒高度(2.43 eV)最接近理论值.当温度高于1 250℃时生成的SiO2栅氧化层的可靠性随之降低.     

太赫兹器件用新型复合多层金刚石材料的研究

微波器件频率进入太赫兹,输能窗的厚度减小至一百甚至几十微米。常规的介质材料,或者多晶金刚石材料已 经难以满足强度和真空密封性能的要求。为此设计并研制出一种新型微/超纳米复合多层金刚石膜。该膜采用微波等离子 体化学气相沉积法（MPCVD）,通过反应气源和沉积参数的改变,实现在硅衬底上依次原位生长微米尺度和超纳米尺度 的金刚石膜。研制的复合多层金刚石膜表面粗糙度Ra<0.5μm,生长面的断裂强度高达1550MPa,是普通多晶金刚石膜的 三倍。用该膜封接的输能窗目前已经通过真空密封性测试,将首次应用于太赫兹真空器件。     

体硅、SOI和SiCMOS器件高温特性的研究

首先介绍了体硅 MOS器件在 2 5～ 30 0℃范围高温特性的实测结果和分析 ,进而给出了薄膜 SOI MOS器件在上述温度范围的高温特性模拟结果和分析 ,最后介绍了国际有关报道的Si C MOS器件在 2 2～ 4 50℃范围的高温特性。在上述研究的基础上 ,提出了体硅、SOI和 Si C MOS器件各自所适用的温度范围和应用前景     

基于ZnO/Al2O3缓冲层制备耐高温SAW器件电极

为了声表面波(SAW)器件能在高温环境(不小于1 000 ℃)中工作,该文设计并在La3Ga5SiO14压电衬底上制作Pt/ZnO/Al2O3多层复合薄膜电极,利用ZnO/Al2O3组合缓冲层增强了Pt薄膜电极在极端高温条件下的导电稳定性。制备的SAW器件在经历3次1 000 ℃高温热处理后仍保持稳定的回波损耗系数S11。实验结果表明,ZnO/Al2O3组合缓冲层结构在提高SAW器件电极高温导电稳定性方面具有一定的潜在应用价值。     

Increasing the Efficiency of Terahertz Generation during the Current Flow through Magnetic Junctions Formed by Inhomogeneous Ultrathin Films of a Ferromagnetic Metal

Operating modes of terahertz (THz) generators with “rod–film” magnetic junctions formed by a Fe rod with one pointed end with a diameter of 10–50 nm and various nanometer-thick (single-layer and multilayer) Со films are studied. It is demonstrated that the efficiency of the THz radiation increases (due to an increase in the current density) if the thickness of a single-layer film decreases to the point when it becomes discontinuous (ultrathin) while retains its conductivity. If a multilayer structure with several such films separated by nonmagnetic conductive layers is used, the radiation power can also be increased.     

Intrinsic Half‐Metallicity in 2D Ternary Chalcogenides with High Critical Temperature and Controllable Magnetization Direction

Searching for 2D ferromagnetic materials with a high critical temperature, large spin polarization, and controllable magnetization direction is a key challenge for their broad applications in spintronics. Here, through a systematic study on a series of 2D ternary chalcogenides with first‐principles calculations, it is demonstrated that a family of experimentally available 2D CoGa₂X₄ (X = S, Se, or Te) are half‐metallic ferromagnets, and they exhibit high critical temperature, fully polarized spin state, and strain‐dependent magnetization direction simultaneously. Following the Goodenough–Kanamori rules, the half‐metallic ferromagnetism of CoGa₂X₄ family is caused by superexchange interaction mediated by Co? X? Co bonds. The half‐metal gaps are large enough (>0.5 eV) to ensure that the half‐metallicity is stable against the spin flipping at room temperature. Magnetocrystalline anisotropy energy calculations indicate that CoGa₂X₄ favor easy plane magnetization. Under achievable biaxial tensile strain (2–6%), the magnetization directions of CoGa₂X₄ can change from in‐plane to out‐of‐plane, providing a route to control the efficiency of spin injection/detection. Further, the critical temperatures T_c of ferromagnetic phase transition for CoGa₂X₄ are close to room temperature. Belonging to the big family of layered AB₂X₄ compounds, the proposed CoGa₂X₄ systems will enrich the available 2D candidates and their heterojunctions for various applications.     

基于PID自整定算法的高精度滤光片热控系统设计

本文介绍了一款基于PID自整定算法的高精度温度控制系统.该系统应用于广角极光成像仪的滤光片组件上,可以达到±0.02℃的测温精度和±0.04℃的控温精度,单路加热片最大输出功率为6W.该系统采用铂电阻作为传感器,使用场效应管和压流转换电路组成的恒流源对加热片进行功率控制.系统使用TMS320C5000系列DSP进行逻辑控制,配合PID算法对滤光片组件进行闭环温控调节.为了提高算法的适应性,系统软件利用时间乘绝对误差的积分(ITAE)准则对控制参数进行自整定.在真空环境下的实验表明,该系统能够实现滤光片高精度的温度控制.     

用于高温和高频领域的PbTiO3基陶瓷的研究

主要研究用于高温和高频领域的PbTiO3基陶瓷的制备工艺、主要性质、显微结构、电导机制及其应用。PbTiO3基陶瓷的性质是与此种陶瓷的制备工艺，显微结构和电导机制紧密相关的。     

Thermal Impact on the Human Oral Cavity Exposed to Radiation from Biomedical Devices Operating in the Terahertz Frequency Range

New medical applications, e.g., aiming at cancer research support, are currently extending the number of technical systems operating in the terahertz (THz) frequency range. This field of applications results in potentially exposed body areas, which have not been taken into account in earlier literature according to exposure assessments at THz frequencies. Due to the small penetration depths in the regarded frequency range, between a few 100 and some micrometers at 0.1 and 10 THz respectively, it was adequate in former analyses to consider near-surface body tissues, e.g., the human eyes or the skin while being exposed to electromagnetic fields. Now, the consideration of body internal tissues becomes necessary since small mobile medical devices can potentially expose tissues underneath the body surface, e.g., inside the oral cavity. In this paper, a multi-level approach is employed in order to estimate electric field strengths and temperature elevations in the human oral cavity by use of numerical computations. Moreover, the urgently needed dielectric properties of the considered tissues, which are not yet available in published databases, are provided here.