碲镉汞薄膜表面钝化的研究进展

赝二元体系碲镉汞(Mercury Cadmium Telluride, Hg_xCd_1-xTe)材料具有优异的光电特性,是制备高灵敏度红外探测器的最重要材料之一。为了获得性能优异的Hg_xCd_1-xTe探测器及其组件,目前已经发展了各种Hg_xCd_1-xTe材料制备技术和器件制作工艺。但在各种材料制备及器件应用过程中,Hg_xCd_1-xTe表面均会受到环境和不良表面效应的影响,所以需要采用先进的钝化工艺对其表面电荷态进行处理,改善材料表面的电学物理特性,从而实现器件探测性能的提升。因此,Hg_xCd_1-xTe薄膜表面钝化工艺对Hg_xCd_1-xTe红外探测器的性能提升至关重要。总结和分析了近年来碲镉汞薄膜表面钝化层的生长方法。按照本源钝化和非本源钝化进行了分类总结和综述,分析了不同钝化方法的优缺点,并对未来碲镉汞薄膜钝化工艺进行了展望。     

分子束外延生长的GaAs-AlxGa1-xAs多层异质结构中的“精细低维调制条纹”的观察

应用透射式电子显微镜观察了GaAs-Al_xGa_1-xAs多层异质结结构中的“精细低维调制条纹”。在邻近GaAs-Al_xGa_1-xAs超晶格层的缓冲层中和与这缓冲层邻近的GaAs-Al_xGa_1-xAs超晶格层的小区域中发现了等宽度的“精细低维调制条纹”,其宽度为9.1Å的GaAs条纹,12Å的Al_xGa_1-xAs条纹。文中介绍了用显微密度计获得的这些条纹的密度分布结果。同时还给出了GaAs-Al_xGa_1-xAs 多层异质结结构的晶格像和用X射线能量散射谱技术获得的成分定量分析结果。     

双色红外焦平面研究进展

介绍了叠层双色红外焦平面的发展背景和适用的材料体系,及其在国际上的发展现状,重点论述了叠层双色探测器结构类型及其探测特点,最后介绍了国内碲镉汞叠层双色焦平面的研究进展。报道了基于n⁺_-p-P-P-N多层异质结Hg_1-xCd_xTe材料的叠层中波/短波（256×1）×2红外双色焦平面器件研制及性能。在77 K液氮温度下,红外焦平面探测器的两个波段的截止波长λ_c分别为2.8 μm和3.9 μm,中波/短波焦平面的平均单色探测率D*_λp分别为1.8×10¹¹ cmHz^1/2/W和9.6×10¹⁰ cmHz^1/2/W。     

InGaAs 可见/短波红外焦平面探测器新进展

In_1-xGa_xAs是一种Ⅲ-Ⅴ族化合物半导体合金材料，其光谱响应截止波长可随合金组分x值的不同在0.87 μm (GaAs)~3.5 μm (InAs)范围内变化。 InGaAs材料在光通讯领域的广泛应用和可在常温下工作的特点，使其成为焦平面成像领域的研究热点。国际市场已有商业化产品，主要应用于民用、军用、航空、空间遥感等领域。在介绍In_1-xGa_xAs短波红外焦平面探测器的主要特性及研制进展的基础上，重点介绍了国际上在InGaAs光谱响应范围向可见光扩展的研究动向。     

新型热释电材料及其在高性能红外探测器中的应用

采用改进的Bridgman法生长出了大尺寸高质量的Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃(PMNT)单晶,并发现了PMNT单晶具有非常大的热释电响应。为探索高性能的热释电材料,提高现有红外探测器的性能,对PMN-PT的热释电性能、及其在红外探测器中的应用进行了系统的研究。研究表明：PMNT单晶具有优异的热释电性能,其综合性能优于传统的热释电材料。用PMNT单晶制备出了的红外探测器,电压响应率和比探测率分别为Rv = 211 V/W,D* = 1.06×108 cm·Hz^1/2·W^-1,器件性能能够基本满足使用要求,同时也表明PMNT单晶有望在高性能的红外探测及成像器件中得到实际应用。     

p型Si1-xGex应变层中重掺杂禁带窄变的计算

针对应变Si_1-xGe_x的应变致价带分裂和重掺杂对裂值的影响,提出了该合金价带结构的等价有效简并度模型。模型中考虑了非抛物线价带结构。应用这个模型,计算了赝晶生长在<100>Si衬底上的p型Si_(1-x)Ge_x应变层的重掺杂禁带窄变,发现当杂质浓度超过约2～3×10¹⁹cm^-3后,它在某一Ge组分下得到极大值,而当掺杂低于此浓度时,它则随Ge组分的增加单调下降。与实验报道的对比证实了本模型的有效性。     

α-Fe2O3薄膜的制备、结构和气敏特性

采用等离子增强化学气相淀积工艺(PECVD)制备出了Fe₂O₃薄膜。用X射线衍射(XRD)和扫描电子显微镜(SEM)分析了薄膜的结构、表面形貌和粒度。研究了薄膜对乙醇、液化石油气、煤气和氢气的敏感特性。结果表明所研制的薄膜对乙醇有较高灵敏度,其检测下限可达1ppm,而对液化石油气、煤气和氢气不太敏感,具有优良的选择性。     

一种用(Pb1/2Ni1/2)MnO3改性的PbTiO3压电陶瓷

<正> 1.引言 由于PbTiO₃压电陶瓷较难合成,因而使它的推广应用比PZT陶瓷晚。但是由于它的介电常数ε小(200左右),居里温度高(490℃),故在高频器件、红外器件等方面有应用前途。目前应用较广的(Ba,Pb)TiO₃-PTC陶瓷的转变温度就是利用PbTiO₃的高温特性来提高的。 本文介绍的是利用PbTiO₃的介电常数小、K_t大和频率稳定度高的特点,把它用作滤…     

0.75PZT-xPZN-(0.25-x)PNN压电陶瓷的相结构和电性能

采用传统固相法制备了0.75Pb(Zr_1/2Ti_1/2)O₃-xPb(Zn_1/3Nb_2/3)O₃-(0.25-x)Pb(Ni_1/3Nb_2/3)O₃(0.75PZTxPZN(_0.25-x)PNN,摩尔分数x=0.05,0.10,0.15,0.20)压电陶瓷,研究了x值对陶瓷晶体结构、烧结特性、微观组织和介电、铁电、压电性能的影响规律。结果表明,陶瓷中三方相和四方相共存,当x=0.10~0.20时,陶瓷组分位于准同型相界(MPB)附近。随着PZN含量的增加,三方相含量减少,四方相含量增加,陶瓷的介电常数(ε_T)、压电常数(d₃₃)、机电耦合系数(k_p)和能量转化因子(d₃₃×g₃₃)均随之先增大后减小,当x=0.15时,0.75PZT-0.15PZN-0.10PNN陶瓷具有最佳电学性能,即ε_T=1 850,公电损耗tan δ=0.029,居里温度T_C=280 ℃,d₃₃=370 pC/N,k_p=0.67。     

PZT纳米铁电薄膜的生长行为和介电性能及微结构

采用溶胶-凝胶(sol-gel)自旋涂敷法在Si(100)基多孔氧化铝模版介质上制备了Pb(Zr0.53Ti0.47)O3(PZT)纳米铁电薄膜(厚度25nm).利用电化学方法在多孔氧化铝模版孔道内(孔径25nm)生长Au纳米线,作为底电板一部分.利用x射线衍射(XRD)、扫描电镜(SEM)及场发射透射电镜(FE-TEM)对PZT纳米铁电薄膜的生长行为、表面形貌和微结构进行了研究.XRD谱图表明PZT纳米铁电薄膜具有(111)择优取向;SEM像显示PZT纳米铁电薄膜结构致密,晶粒呈椭球状,平均尺寸为22nm.剖面TEM像证实PZT纳米铁电薄膜与Au纳米线直接接触,它们之间的界面呈现一定程度的弯曲;部分Au纳米线顶端出现分枝展宽现象.介电谱表明PZT纳米铁电薄膜的介电常数在低频区域(频率小于104 Hz)从760迅速下降到100,然后基本保持在100,直至测量频率升高到106 Hz.低频区域内介电常数的迅速下降是由于空间电荷极化机制所致;介电损耗在4 000 Hz附近出现峰值(来源于空间电荷的共振吸收)也证实了空间电荷极化机制的存在.     

Microstructure and domain configurations in ferroelectric PbTiO3 and Pb(Zr,Ti)O3 thin fims

Ferroelectric domain configurations in PbTiO₃ and Pb(Zr_xT_1−x)O₃ (PZT, x = 0.3 or 0.5) thin films have been studied by transmission electron microscopy. The PbTiOg and PZT thin films have been deposited by the ionized cluster beam technique and radio frequency sputtering, respectively. The grain size in these thin films is typically less than 0.5 μm. Lamellar 90°-domain features have been observed in both PbTiO₃ and PZT (30/70) samples. The domain walls correspond to the {011} twin boundaries. La-doping and Ca-modification are shown to affect the microstructure of the PZT films. No clear domain feature occurs in the PZT thin film that has composition near the morphotropic phase boundary. The effects of grain sizes are briefly discussed.     

Thermo-Sensitive Ba0.64Sr0.36TiO3 Thin Film Capacitors for Dielectric Type Uncooled Infrared Sensors

Ba_0.64Sr_0.36TiO₃ (BST) thin films are prepared on Pt/Ti/SiO₂/Si₃N₄/SiO₂/Si substrates by a sol-gel method. Thermo-sensitive BST thin film capacitors with a Metal-Ferroelectrics-Metal (M-F(BST)-M) structure are fabricated as the active elements of dielectric type uncooled infrared sensors. XRD are employed to analyze the crystallographic structures of the films. AFM observations reveal a smooth and dense surface of the films with an average grain size of about 35 nm. Rapid temperature annealing (RTA) process is a very efficient way to improve crystallization quality. The preferable annealing temperature is 800°C for 1 min. The butterfly shaped C-V curves of the capacitors indicate the films have a ferroelectric nature. The dielectric constant and dielectric loss of the films at 100 kHz are 450 and 0.038, respectively. At 25°C, where the thermo-sensitive capacitors work, the temperature coefficient of dielectric constant (TCD) is about 5.9 %/°C. These results indicate that the capacitors with sol-gel derived BST thin films are promising to develop dielectric type uncooled infrared sensors.     

Optimizing the Charge Carrier Dynamics of Thermal Evaporated TexSe1-x Films for High-Performance Short-Wavelength Infrared Photodetection

Short-wavelength infrared photo-sensing materials are dominated by germanium, indium gallium arsenide, indium antimonide, and mercury cadmium telluride. However, the complex fabrication process and high production cost hinder their widespread applications. Recently, Te_xSe_1-x has shown great potential for infrared photodetection, but Te_xSe_1-x-based devices are still suffering from extremely high dark current and poor device performance. In this work, high-quality Te_xSe_1-x films are fabricated by thermal evaporation and low-temperature annealing. The optoelectronic properties of the Te_xSe_1-x thin films are systematically investigated and optimized. The absorption spectrum is carefully tuned to cover the broad range from 300 to 1600 nm by modulating the ratio of Te and Se. Photodiodes based on the optimized Te_xSe_1-x thin films are also fabricated, and achieve high responsivity, reduced dark and low noise current density, and a fast response time of <850 ns. Then, prototypical devices based on Te_0.65Se_0.35 thin films are demonstrated for optical communications, indicating the great potential for next-generation, low-cost short-wavelength infrared photodetection.     

Highly (1 0 0)-oriented Pb(Zr0.20Ti0.80)O3/(Pb1−xLax)Ti1−x/4O3 multilayered thin films prepared by RF magnetron sputtering

The Pb(Zr_0.20Ti_0.80)O₃/(Pb_1−xLa_x)Ti_1−x/4O₃ (x = 0, 0.10, 0.15, 0.20) (PZT/PLT_x) multilayered thin films were in situ deposited on the Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by RF magnetron sputtering technique with a PbO_x buffer layer. With this method, all PZT/PLT_x multilayered thin films possess highly (1 0 0) orientation. The PbO_x buffer layer leads to the (1 0 0) orientation of the multilayered thin films. The effect of the La content in PLT_x layers on the dielectric and ferroelectric properties of the PZT multilayered thin films was systematically investigated. The enhanced dielectric and ferroelectric properties are observed in the PZT/PLT_x (x = 0.15) multilayered thin films. The dielectric constant reaches maximum value of 365 at 1 KHz for x = 0.15 with a low loss tangent of 0.0301. Along with enhanced dielectric properties, the multilayered thin films also exhibit large remnant polarization value of 2P_r = 76.5 μC/cm², and low coercive field of 2E_c = 238 KV/cm.     

Magnetron-assisted deposition of thin (SiC)1-x(AlN)x alloy films

The results of theoretical estimations of important parameters of the process of magnetron-assisted sputtering are reported. The parameters are the extent of the zone of thermalization of atoms and the distance from the target to the conditional anode. The method of magnetron-assisted sputtering of polycrys-talline SiC-AlN targets is applied to produce thin (SiC)_1-x(AlN)_x alloy films on SiC and Al₂O₃ substrates. The structure and composition of the films are studied by X-ray diffraction measurements and electron microscopy. The factors that control the composition and structure of the films and the conditions of formation of the single-crystal (SiC)_1-x(AlN)_x films on the SiC substrates are established.     

Structural and optical properties of hexagonal MgxZn1−xO thin films

High-quality epitaxial magnesium zinc oxide (Mg_xZn_1-xO) alloy thin films were grown on sapphire (α-Al₂O₃ (0001)) substrates using pulsed laser deposition. The structural and optical properties of these hexagonal films were determined using transmission electron microscopy (TEM), x-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), absorption, and photoluminescence measurements. XRD and TEM data reveal that magnesium zinc oxide alloy films, grown by domain matching epitaxy, exhibited the following relationships: MgZnO[0001] ∥ α-Al₂O₃ [0001] and MgZnO[01 0] ∥ α-Al₂O₃ [2 0]. RBS data demonstrate that a maximum magnesium content of x=0.34 can be obtained in hexagonal Zn_xMg_1-xO thin films. This value is significantly higher than the thermodynamic limitation of x=0.04. The absorption spectra of magnesium zinc oxide alloy films obtained at room temperature demonstrate significant excitonic behavior. The exciton binding energies have been extracted from the absorption data. Values of the exciton bandgap as a function of magnesium content were determined by fitting the bandgap energies using polynomial fitting. The Zn_xMg_1−xO alloy thin films demonstrate bright room-temperature luminescence and significant excitonic behavior. A shift in the excitonic emission peak as a function of magnesium content was observed.     

Fabrication of Relaxer-Based Piezoelectric Energy Harvesters Using a Sacrificial Poly-Si Seeding Layer

The effect of a polycrystalline silicon (poly-Si) seeding layer on the properties of relaxor Pb(Zr_0.53,Ti_0.47)O₃–Pb(Zn_1/3,Nb_2/3)O₃ (PZT–PZN) thin films and energy-harvesting cantilevers was studied. We deposited thin films of the relaxor on two substrates, with and without a poly-Si seeding layer. The seeding layer, which also served as a sacrificial layer to facilitate cantilever release, was found to improve morphology, phase purity, crystal orientation, and electrical properties. We attributed these results to reduction of the number of nucleation sites and, therefore, to an increase in relaxor film grain size. The areal power density of the wet-based released harvester was measured. The power density output of the energy harvester with this relaxor composition and the poly-Si seeding layer was 325 μW/cm².     

Large area depositon of Cd1-xZnxTe on GaAs and Si substrates by metalorganic chemical vapor deposition

Results of large-area (up to 1000 cm²/run) Cd_1-xZn_xTe heteroepitaxy on both GaAs and GaAs/Si substrates by metalorganic chemical vapor deposition (MOCVD) are presented. Cd_1-xZn_xTe (x = 0-0.1) films exhibited specular surface morphology, 1% thickness uniformity (standard deviation), and compositional uniformity (Δx) of ±0.002 over 100 mm diam substrates. For selected substrate orientations and deposition conditions, the only planar defects exhibited by (lll)B Cd_1-xZn_xTe/GaAs/Si films were lamella twins parallel to the CdTe/GaAs interface; these do not propagate through either the Cd_1-xZn_xTe layer or subsequently deposited liquid phase epitaxy (LPE) HgCdTe layer(s). Background Ga and As-impurity levels for Cd_1-xZn_xTe on GaAs/Si substrates were below the secondary ion mass spectroscopy detection limit. Preliminary results of HgCdTe liquid phase epitaxy using a Te-rich melt on Si-based substrates resulted in x-ray rocking curve linewidths as narrow as 72 arc-sec and etch-pit densities in the range 1 to 3 x 10⁶ cm².     

Study of the optical features of YBa2Cu3O7-x films by SEW spectroscopy

The results of YBa₂Cu₃O_7-x films on SrTiO₃ investigation by far infrared surface electromagnetic waves (SEW) amplitude and phase spectroscopy at temperatures 80–350 K are presented. Strong SEW absorption at frequency 142 cm^?1 has been observed. The origin of the observed absorbtion is proposed to be concerned with slab- phonons in YBa₂Cu₃O_7-x. The optical constants of the films have been obtained. Also has been determined, that only the imaginary part of the SEW refraction index changes when the film transits into superconducting state, while the real part remains unchanged.