SiGe薄膜材料的椭圆偏振光谱研究

采用椭圆偏振光谱(SE)对一系列SiGe样品进行了研究。确定了SixGe1-x层的厚度和组分;对不均匀的SixGe1-x层,沿厚度方向进行了组分梯度的研究,其结果与二次离子质谱(SIMS)的测试有较好的一致性;成功地表征了器件级绝缘体上的硅锗(SGOI)样品的各层结构和SixGe1-x层的组分。     

Ga contamination in silicon by Focused Ion Beam milling: Dynamic model simulation and Atom Probe Tomography experiment

Focused Ion Beam (FIB) milling is a widely used and important technique to prepare Transmission Electron Microscopy (TEM) lamella samples. However, it unavoidably introduces contamination in the samples like implanted ions. While the conventional ion-solid simulation model, Binary Collision Approximation (BCA), is unable to describe the FIB process, a dynamic BCA model is used in this study to predict the level of Ga implantation along the substrate depth. The FIB process involves significant material transport and local composition alteration, which requires a dynamic model for simulation. To validate the dynamic BCA model's application on simulating the FIB process, atomic level composition analysis Atom Probe Tomography (APT) is performed on Ga FIB processed silicon samples. The experimental data confirm that the dynamic BCA model is capable to predict FIB induced Ga ion implantation in silicon samples.     

Structure of the Cu<Subscript>2</Subscript>Se compound produced by different methods

Copper-selenide (Cu₂Se) samples are produced by mechanochemical synthesis and compaction by spark plasma sintering and hot pressing. The structure and phase composition of the samples before and after heat treatment are studied by the X-ray diffraction technique and electron microscopy. The character of changes in the shape and size of structural elements of the samples is shown. Variations in the phase composition of copper selenide in the temperature range from 25 to 500°C are studied in situ.     

Nanostructure of Er3+ doped silicates

We demonstrate nanostructural evolution resulting in highly increased photoluminescence in silicates doped with Er3+ ions. High-resolution transmission electron microscopy (HRTEM) imaging, nano-energy dispersed X-ray (NEDX) spectroscopy, X-ray diffraction (XRD) and photoluminescence analysis confirm the local composition and structure changes of the Er3+ ions upon thermal annealing. We studied two types of amorphous nanopowder: the first is of the composition SiO2/18Al2O3/2Er2O3 (SAE), synthesized by combustion flame-chemical vapor condensation, and the second is with a composition of SiO2/8Y2O3/2Er2O3 (SYE), synthesized by sol-gel synthesis (composition in mol%). Electron diffraction and HRTEM imaging clearly show the formation of nanocrystallites with an average diameter of approximately 8 nm in SAE samples annealed at 1000 degrees C and SYE samples annealed at 1200 degrees C. The volume fraction of the nanocrystalline phase increased with each heat treatment, eventually leading to complete devitrification at 1400 degrees C. Further XRD and NEDX analysis indicates that the nanocrystalline phase has the pyrochlore structure with the formula Er(x)Al(2-x)Si2O7 or Er(x)Y(2-x)Si2O7 and a surrounding silica matrix.     

Structural properties of GaAsN grown on (001) GaAs by metalorganic molecular beam epitaxy

Detailed transmission electron microscopy (TEM) and transmission electron diffraction (TED) examination has been made of metalorganic molecular beam epitaxial GaAsN layers grown on (001) GaAs substrates. TEM results show that lateral composition modulation occurs in the GaAs_1−xN_x layer (x 6.75%). It is shown that increasing N composition and Se (dopant) concentration leads to poor crystallinity. It is also shown that the addition of Se increases N composition. Atomic force microscopy (AFM) results show that the surfaces of the samples experience a morphological change from faceting to islanding, as the N composition and Se concentration increase. Based on the TEM and AFM results, a simple model is given to explain the formation of the lateral composition modulation.     

Characterization of GaNxAs1-x Alloy Grown on GaAs by Molecular Beam Epitaxy

Ga Nx As1 - x,the combination of small amount of nitrogen and Ga As,has beenexperimentally observed with the band gaps several hundreds me V lower than that ofGa As[1～ 4] .The alloy has attracted considerable attention in the applicat...     

Characterization of GaNxAs1-x Alloy Grown on GaAs by Molecular Beam Epitaxy

The GaNxAs1-x alloy has been investigated which is grown on GaAs (100) substrate by molecular beam epitaxy with a DC-plasma nitrogen source. The samples are characterized by high resolution X-ray diffraction (HRXRD) and low temperature photoluminescence (PL) measurements. Both HRXRD and PL measurements demonstrate that the crystalline and optical qualities of GaNxAs1-x alloy degrade rapidly with the increase of N composition. The nitrogen composition of 4.5 % can be obtained in GaNxAs1-x/GaAs quantum well by optimizing growth conditions,through which a photoluminescence peak of 1201nm is observed at a low temperature (10 K). The dependence of GaNxAs1-x band gap energy on the nitrogen composition in this investigation corresponds very well with that of the theoretical one based on the dielectric model when considering the effect of the strain. At the same time,we also demonstrate that the bowing parameter of GaNxAs1-x alloy is composition dependent.     

准同型相界附近PMN-PT陶瓷的介电性能

采用铌铁矿预产物合成法制备了组成在相界附近的(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-PT)弛豫铁电陶瓷。陶瓷样品X-射线衍射相组成和相结构分析表明:所有陶瓷样品均为纯钙钛矿相,无任何其他杂相出现;且组成在x=0.33处存在一准同型相界(MPB),在该相界附近三方相和四方相共存,而远离该相界则分别为纯三方相和四方相。相界附近组成随PT摩尔分数增加,介电峰变得尖锐,频率弥散减弱,即介电弛豫程度减弱。这主要是由于四方相增多,三方相减少,从而使弛豫铁电体变为正常铁电体。     

HgCdTe液相外延材料组分分布的红外透射光谱评价技术

对红外透射光谱法测定HgCdTe液相外延材料纵向组分分布技术进行了深入的研究.红外透射光谱的理论计算采用了王庆学提出的组分分布模型,并考虑了光穿越组分梯度区时产生的干涉效应.通过测量同一样品在不同外延层厚度下的一组红外透射光谱,该方法的有效性得到了实验验证.进一步对组分模型中参数(即外延总厚度、组分互扩散区厚度、材料表面组分和HgCdTe层组分梯度)的拟合方法进行了讨论,并确定了各拟合参数的拟合精度.结果显示,该方法可作为测定HgcdTe液相外延材料组分特性的一种有效的测试评价技术.     

喇曼光谱仪测定芳烃装置中各组分含量的研究

为了提高在线喇曼光谱仪在芳烃装置的组分检测中的实时性和精度,采用偏最小二乘法(PLS)结合粒子群算法(PSO)建立了预测模型。对一定的芳烃样品进行试验。先通过光谱仪获得芳烃成分的喇曼光谱,再运用PLS算法对喇曼数据进行主因子提取,从而降低数据间的冗余性,然后应用PSO算法对芳烃组分含量进行快速搜索,找到最优解,最后将样品的真实值与预测值进行相关性分析。结果表明,与传统方法相比,喇曼光谱结合PSO算法和PLS算法的模型具有精确度高、分析速度快的特点。该研究为芳烃装置中组分的检测提供了新方法。     

HgCdTe composition determination using spectroscopic ellipsometry during molecular beam epitaxy growth of near-infrared avalanche photodiode device structures

The application of spectroscopic ellipsometry (SE) for real-time composition determination during molecular beam epitaxy (MBE) growth of Hg_1−xCd_xTe alloys with x>0.5 is reported. Techniques previously developed for SE determination of composition in long-wavelength infrared (LWIR) HgCdTe have been successfully extended to near-infrared HgCdTe avalanche photodiode (APD) device structures with x values in the range of 0.6–0.8. Ellipsometric data collected over a spectral range of 1.7–5 eV were used to measure depth profiles of HgCdTe alloy composition through the use of an optical model of the growth surface. The optical model used a dielectric-function database collected through the growth of a set of HgCdTe calibration samples with x ranging from 0.6 to 0.8. The sensitivity of this SE method of composition determination is estimated to be Δx ∼0.0002 at x=0.6, which is sufficiently low to sense composition changes arising from flux variations of less than 0.1%. Errors in composition determination because of Hg-flux variations appear to be inconsequential, while substrate-temperature fluctuations have been observed to alter the derived composition at a rate of −0.0004/°C. By comparing the composition inferred from SE and postgrowth 300 K IR transmission measurements on a set of APD device structures, the run-to-run precision of the Se-derived composition (at x=0.6) is estimated to be ±0.0012, which is equivalent to the precision achieved with the same instrumentation during the growth of mid-wavelength infrared (MWIR) HgCdTe alloys in the same MBE system.     

Low-energy electron-enhanced etching of HgCdTe

Low-energy electron-enhanced etching (LE4) is applied to HgCdTe to eliminate ion-induced surface damage. First, LE4 results for patterned samples are illustrated. The LE4 mechanism is understood from a mechanistic study in terms of three etch variables: direct current (DC) bias, gas composition, and sample temperature. For this paper, the effects of DC bias (electron energy) and gas composition (CH₄ concentration) are summarized qualitatively, followed by quantitative evidence. Etch rate, the amount of polymer, surface stoichiometry, and surface roughness have specific relations with each etch variable under competition between pure LE4 and polymer deposition.     

Impact of compositionally graded base regions on the DC and RF properties of reduced turn-on voltage InGaP-GaInAsN DHBTs

Built-in drift fields are employed to enhance the performance of GaAs-based heterojunction bipolar transistors (HBTs) with reduced turn-on voltage. Specifically, we explore in detail the dc and RF device property improvements enabled by using compositionally graded GaInAsN base layers. Experimental results are compared to predictions of the standard drift-diffusion base transport model employing a finite exit velocity. In large area devices, graded base samples with built-in fields of /spl sim/7 kV/cm (i.e. 40 meV over 500 /spl Aring/) typically have a dc current gain 1.8/spl times/ larger than constant base composition samples. In small area devices, the peak cut-off frequency is typically 10%-15% higher than constant composition samples. These results are shown to agree reasonably well with predictions, thereby demonstrating that analytical drift-diffusion based models can be extended to HBTs with GaInAsN base layers.     

Si基片上掺Ge SiO_2的火焰水解法制备

用火焰水解法在单晶Si片上沉积了掺Ge的SiO2 (GeO2 SiO2 )粉末 ,随后在高温炉中将此粉末烧结成玻璃 .用光学显微镜观察了样品表面形貌 ,研究了不同的烧结工艺对样品形貌的影响 .用X射线光电子能谱检测了样品的元素组成 ,并用棱镜耦合法测量了样品的折射率和厚度 .结果表明 ,用适宜的工艺条件制备出的掺Ge的SiO2 具有表面平整光滑 ,折射率和厚度可调等优点 ,适合用作Si基SiO2 波导器件的芯层 .     

烷基化汽油中烃类物质含量的太赫兹时域光谱研究

应用太赫兹时域光谱技术研究了烷基化汽油中烯烃在太赫兹波段的性质。以烷基化汽油中的2,4,4-三甲基戊烯为例,分析了其不同浓度在太赫兹波段产生的光谱响应。结果表明, 对于烯烃含量不同的烷基化汽油,其信号中的峰强具有明显不同,并浓度的变化呈线性变化。利用时域谱最大值和最小值之和拟合而成的预测曲线对两种未知浓度样品进行预测,其误差均小于0.5%。同时对其不同频率下的吸收系数进行拟合与分析。根据太赫兹光谱最原始的幅值信息及其吸收系数可对其中烯烃含量进行快速定性,甚至是定量分析, 为烷基化汽油中烃含量和品质的定量检测作基础。     

Optical properties of porous silicon layers processed with a HF:HCI:C2H5OH electrolyte

The properties of porous silicon samples prepared by adding hydrochloric acid to the usual hydrofluoric-acid electrolyte have been studied. These samples exhibit an intense photoluminescence that does not degrade over time and is unaffected by exposure to intense laser illumination. The peak photoluminescence from these layers of porous silicon occurs at photon energies of 1.85–1.9 eV. The photoluminescence signal from samples prepared in the standard way under the same initial conditions but without HCl in the composition of the electrolyte is two orders of magnitude less intense. Studies of the degradation of these porous silicon samples with time and exposure to various power levels of laser illumination revealed that the samples with the maximum content of HCl in the electrolyte composition emitted photoluminescence that was unaffected by laser illumination. In this work, the infrared spectra of the samples was measured in order to monitor the chemical state of their surfaces. It was found that the abrupt 100-fold increase in the intensity of the photoluminescence signal from samples made according to the method proposed here is associated both with distinctive features of the structure of porous silicon layers and with the presence of a thin crystalline layer of SiO₂ on the surface of nanocrystallites. Fiz. Tekh. Poluprovodn. 33, 198–204 (February 1999)     

Slow-Polishing Iodine-Based Etchant for CdTe and CdZnTe Single Crystals

We report on new etching solutions for treatment of CdTe and CdZnTe surfaces based on the iodine-emerging etchant composition KIO₃–KI–citric acid (C₆H₈O₇). CdTe samples with (111), (110), and (100) orientations, and also Cd_1?x Zn _x Te (x?=?0.04, 0.1) samples with (111), (110), (100), and (211) orientations were investigated. The dissolution rate was determined as a function of solution composition, etchant storage time, disc rotation speed, and temperature. It was established that this chemical dissolution is diffusion controlled. Study of the chemical composition and structure of (211)B Cd_1?x Zn _x Te surfaces etched under different conditions was carried out. x-Ray photoelectron spectroscopy measurements showed that a stoichiometric surface was achieved after briefly heating the etched surface in a vacuum. Reflection high-energy electron diffraction measurements revealed a high-quality single-crystalline surface layer in samples etched with KIO₃–KI–citric acid solutions as compared with those etched with a bromine–methanol treatment. The etching compositions were shown to be useful for controlled removal of semiconductor material, and also for chemical polishing of CdTe-based surfaces.     

采用As2和As4模式的新型全固源InAsP分子束外延生长

在国产分子束外延设备的基础上,利用新型阀控裂解As源炉,对As2和As4的生长特性进行了全面的研究.以As2和As4两种模式,在(001)InP衬底上生长了高质量的InAsP体材料和InAsyP1-y/InP多量子阱样品.材料质量用X射线衍射(XRD)以及室温和低温的光致发光(PL)测定.实验发现,两种模式生长的样品的晶体结构质量相当,但As2的吸附系数明显大于As4的吸附系数.另外,用As2模式生长的多量子阱样品的室温光学特性优于As4模式生长的样品,但在低温时,二者几乎相同,这是由As4较为复杂的生长机制所引入的缺陷造成的.     

太赫兹双磁矩环偶极子传感芯片及其在原油检测中的应用

原油样品中主要成分的快速检测及产地溯源对国防安全及生态环境等领域意义重大。现阶段的原油成分检测操作复杂、成本高且检测时间较长,无法满足对原油成分的快速检测及原油产地快速溯源的需求。文中结合高灵敏太赫兹检测芯片(基于双磁矩环偶极子）和时域太赫兹波谱系统,测试了不同产地原油样品的太赫兹光谱,发现芯片谐振峰频移呈现不同的规律。且对于原油中两个最主要的指标硫含量和残碳量,可分别根据它们的频移规律进行定量分析。实验数据计算表明:相同产地的原油的谐振频率平均值相对差值平均为4.63%,不同产地的原油的谐振频率平均值的相对差值平均为56.53%,可明显区分出原油的产地。设计的超表面芯片激发了电磁新模式,提供了一种高灵敏度的检测技术,可广泛应用于生物分子实时监测或探测化学物质(如原油)成分检测、产地溯源等领域。     

稀土锰氧化物Sm1-xBaxMnO3的结构、红外及电性能研究

采用传统固相反应法,制备了一系列钙钛矿结构的稀土锰氧化物Sm<,1-x>Ba<,x>MnO<,3>(x=0～0.5)样品,借助XRD和FTIR对样品的相结构和组成进行了研究,用四端子法测量了样品在室温下的电导率.结果表明,当x<0.4时,样品为单一的钙钛矿结构;当0.4≤x≤0.5时,样品为Sm<,1-x>Ba<,x....