An Analysis of Germanium–Silicon/Silicon Strained Superlattice Structure Using Convergent Beam Electron Diffraction

Strained superlattices (SSLs) are typically found inside the p‐n junction area of semiconductor devices and consist of very thin alternating layers of different material. There exists a small lattice mismatch between these materials which results in localised strain, as in the case of germanium‐silicon/silicon SSLs. Strain measurements using a convergent beam electron diffraction (CBED) technique inside a transmission electron microscope (TEM) have indicated that the strain measured normal to these germanium–silicon/silicon SSLs varies almost sinusoidally, in spite of theoretical predictions which indicate a much sharper change in strain between these layers. A theoretical formulation involving an elasticity solution has been developed to predict the strain inside these SSL structures. The comparison of theoretical and experimental results clearly quantifies the effect of beam size on the spatial resolution of CBED measurements. Given that beam size is critically dependent on the spot size of the beam, the convergence angle, the specimen thickness and the position of the focused plane, these parameters are all clearly accounted for in the theoretical predictions.     

Structural Properties of Doped GaN on Si(111) Studied by X-Ray Diffraction Techniques

X-ray diffraction (XRD) is a non-destructive technique which is widely used in material characterization, particularly to determine structure, crystalline quality and orientation of samples. Two representative samples are used in this work, these samples are sample I (Si-doped GaN/AlN/Si) nominally consisted of 284 nm AlN followed by 152 nm of Si-doped GaN, and sample II (Mg-doped GaN/AlN/Si), grown with 194 nm AlN followed by 136 nm of Mg-doped GaN. Both doped GaN films were investigated by high resolution X-ray diffraction (HRXRD) with rocking curve (RC) measurement around the symmetrical (0002) and asymmetrical (10 $\overline{1}$ 2) diffraction peaks. The phase analysis result revealed that monocrystalline GaN was obtained. The XRD pattern show sharp and well separated (000l) reflections of doped GaN and AlN indicating complete texture with GaN[0?0?0?2] ∥ AlN[0?0?0?2] ∥ Si[1?1?1]. From the HRXRD RC ω/2θ scans of (10 $\overline{1}$ 2) and (0002) plane, we determined both a and c lattice parameters of the doped GaN. The symmetrical and asymmetrical RC full width at half maximum (FWHM) of doped GaN were obtained.     

X-Ray Diffraction Analysis of Epitaxial Layers with the Properties of a Dislocation Filter

An approach to instant testing of epitaxial films with a sharp decrease in the threading dislocation density is proposed. High-resolution X-ray diffractometry, including reciprocal space mapping, has been used. The structure of GaAs/Si(001) heterosystems with low-temperature GaAs layers has been analyzed. A decrease in the density of threading dislocations in the GaAs film with the formation of a small-angle boundary has been detected.     

Residual Stresses Comparison Determined by Short-Wavelength X-Ray Diffraction and Neutron Diffraction for 7075 Aluminum Alloy

High strength Al alloy 7075 is widely used in aeronautic and space domains. However, when the thick plate of 7075 alloy is quenched improperly, large residual stress (RS) will be produced which leads to the loss of performance in resistance corrosion, fatigue and fracture. It is necessary to get the detailed information about residual stress distribution in the quenched plate. Conventional X-ray diffraction, a viable residual stress test method, can only reveal the RS state near surface layer due to limited penetrated depth. RS in the bulk components now can usually be analyzed by neutron diffraction or hard X-ray diffraction of high energy synchrotron in non-destructive way. Here a novel non-destructive method using short-wavelength characteristic X-ray diffraction meter (SWXRD) with the X-ray tube of tungsten anode target to determine the RS within the materials is developed in China. This paper revealed the RS distribution in a 20 mm thick plate of 7075 Al alloy determined by SWXRD and typical neutron diffraction (in LLB laboratory of France). The RS distribution through the thickness of Al plate shows a good agreement with the result determined by SWXRD compared with neutron diffraction.     

Grinding of Single-Crystal Silicon Along Crystallographic Directions

This article studies the effect of grinding along crystallographic directions on the surface finish of single-crystal silicon. It also discusses new and/or improved processes for precision machining brittle materials, including silicon. Silicon samples were cut from (100) silicon wafers. These samples were then subjected to grinding along different crystallographic directions under the same experimental conditions. The surface roughness and the surface texture of these samples were then analyzed. The R_aand R_qvalues and the microphotographs of the ground silicon surfaces showed the dependency of surface finish on the grinding direction. Better surface finish was achieved when (100) silicon was ground along 〈110〉 directions. Samples ground along these directions also showed more ductile streaks on the silicon surfaces, compared with surfaces ground along the other directions.     

Langmuir-Blodgett膜的低角X射线衍射分析

低角X射线衍射是研究LB膜结构的有力工具,它能确认LB膜中成膜分子的排列规则性,确定LB膜的等同周期,计算LB膜厚,确定LB膜类型,成膜分子在基片上的倾斜角度和两种分子在混合LB膜中的排列,研究成膜分子在LB膜上的聚合,LB膜在酸碱环境下的稳定性,衍射峰的奇偶起伏现象等。     

Time-Resolved Characterization of Ferroelectrics Using High-Energy X-Ray Diffraction

Diffraction provides an effective means to characterize ferroelectric materials under the application of dynamic and cyclic electric fields. This paper describes a typical timeresolved diffraction setup at a synchrotron facility using high X-ray energies. Such a setup is capable of measuring the structural response of ferroelectric ceramics to electric fields of various frequencies, amplitudes, and waveforms. The use of high energies also allows the response of the sample to be measured at various angles to the applied load. The results of 3 different types of electric loading are presented and discussed: the structural response of ferroelectric ceramics to a single electric field step function, a cyclic electric field of square waveform, and a cyclic electric field of sinusoidal waveform. Each type of electric field loading provides unique information about the material behavior.     

碳电极材料石墨化度和无序度的X射线衍射测定

介绍了测定碳电极材料石墨化度g和无序度P的X射线衍射(XRD)原理与方法,包括从二维(1 0)和(1 1)衍射的Fourier分析、全谱拟合法以及利用石墨化度g与d002之间的关系曲线的方法.提出由θ002求g的方法和新公式.进行了石墨化度与无序度测定的实验研究,包括不同实验条件对全谱拟合结果的影响、不同求解d002的影响,以及d002法、θ002法与全谱拟合法的比较.结果表明,全谱拟合法求得的无序度Pwsf在用d002法的直线和曲线测得的结果之间,d002法和θ002法测得的g符合很好.提出全谱拟合法和用Si粉作内标样的d002及θ002法的衍射实验测定最佳方案.     

激光粒度仪颗粒联测的结果与评价

为了解不同激光粒度仪的硬件、软件等方面差异对粒度测量结果的影响,用4种颗粒形状不同的粉末在不同公司生产的激光粒度仪上进行测试。结果表明:激光粒度仪测试结果重复性很好;对于球形粉末和形状较规则的粉末,大部分激光粒度仪测得的中位径值之间可以比较;而粒径范围较宽和不规则形状粉末,个别仪器测量的中位径值有差异。     

Consistent Relationship Between the Tunnel Magnetoresistance of CoFeB/MgO/CoFeB Junctions and X-Ray Diffraction Properties

We have investigated the effect of Ar pressure during MgO sputtering on the tunnel magnetoresistance (TMR) and resistance area (RA) product of CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs). The TMR of MTJs with a thin MgO tunnel barrier deposited at different Ar pressures (1.3, 4, 10, and 25 mTorr) shows a consistent relationship with x-ray diffraction (XRD) properties of thick MgO films deposited with the same conditions. The deposition of the MgO-barrier at 1.3 mTorr results in a low TMR ratio and a high RA product due to the disordered MgO barrier and the oxidation of the bottom electrode of the MTJ, while the deposition at 25 mTorr results in a rough MgO barrier, and thereby gives rise to a large shift of switching field of the free layer due to the orange-peel coupling.      

Study of a Pure-Ge/Si Short-Period Superlattice by X-Ray Double Crystal Diffraction

Pure-Ge/Si short-period superlattice (SPS) samples consisting of 1.5-monolayer Ge and a 1.4- to 3.8-nm-thick Si layer grown by gas source molecular beam epitaxy (GS-MBE) were studied by double-crystal x-ray diffraction. For SPS with a Si layer less than 2.4 nm, the satellite peak caused by the SPS structure in the rocking curve is quite broad, and no fine structure is found, indicating that there exists dislocation and waviness epilayers in the SPS. For SPS with a thick Si layer, the rocking curve is sharp and fine interference structures exist, indicating smooth epilayers in the SPS. It is found that both broad and sharp peaks exist but without fine structure in the rocking curves for SPS samples with a Si layer thickness (L _Si) in the range of 2.1–2.9 nm, which is the range in which an abnormal photoluminescence band appears in photoluminescence spectra. This result strongly supports H. Sunamura's suggestion that the abnormal photoluminescence band is caused by waviness formation of the epilayer due to vertical correlation of thickness fluctuations by the local strain field.     

The Determination of relative amounts of Phases in Binary Mixtures with Quantitative X-Ray Diffraction

Abstract

The quantitative x-ray diffraction analysis offers often an exact and practical technique to determine the relative amounts of the phases of the solid in question. The sample may contain only one amorphous phase.

The purpose of this paper is to estimate the suitability of this technique to quantify the phase fractions of pharmaceutical substances. Three different method were used to determine the relative amounts of phases. Methods were compared and the major sources of error were estimated. The measurements and calculations are carried out using selegilin hydrochloride, mannitol and modified starch as an example. The results show that the amount of about 2 % of selegilin hydrochloride can be observed reliably from among the mannitol (crystalline substance) or modified starch (amorphous substance). During the work it became obvious that the accuracy of these calculations can essentially be improved planning the measurements carefully.     

用于太阳能电池的多晶硅锭片晶体学特征研究

用背散射电子衍射分析技术研究铸造多晶硅锭切片的晶体学特征.结果表明:多晶硅锭晶体内部几乎没有取向差,取向差主要存在于晶界处;多晶硅锭切片中的大部分晶界为大角度晶界,且以Σ3为主,同时还存在少量小角度晶界.多晶硅制作太阳能电池转换率低可能与Σ3所占比例过高有关.     

The Determination of relative amounts of Phases in Binary Mixtures with Quantitative X-Ray Diffraction

The quantitative x-ray diffraction analysis offers often an exact and practical technique to determine the relative amounts of the phases of the solid in question. The sample may contain only one amorphous phase.

The purpose of this paper is to estimate the suitability of this technique to quantify the phase fractions of pharmaceutical substances. Three different method were used to determine the relative amounts of phases. Methods were compared and the major sources of error were estimated. The measurements and calculations are carried out using selegilin hydrochloride, mannitol and modified starch as an example. The results show that the amount of about 2 % of selegilin hydrochloride can be observed reliably from among the mannitol (crystalline substance) or modified starch (amorphous substance). During the work it became obvious that the accuracy of these calculations can essentially be improved planning the measurements carefully.     

X-Ray Diffraction Study of Correlated Electron System at Low Temperatures

By using an ultra-low temperature X-ray diffractometer, we studied low temperature phase transitions of several materials. These phase transitions are classified into a ferro quadrupole ordered phase, that is, Jahn–Teller distortion (TmVO, ZnCrO), an antiferro quadrupole ordered phase (CeB, PrPb), and a superconducrivity (MgB). We also investigated unknown phases, such as the low temperature phase in PrPtBi and the 4th phase in CeLaB. Our low temperature X-ray measurement gives rise to a fruitful information about the phase transition. Not only a whole profile of the reflection peaks, which can be analyzed by the Rietveld method, we also made the precise measurement of the temperature dependence of the integrated intensity of the reflection peak, the full width at half maximum, and the lattice spacing for some fixed reflections. The temperature dependence of the integrated intensity (I.I.) can be expressed by the Debye–Waller expression. At low temperatures, the change of the phonon frequency can be obtained from the I.I. through the Debye–Waller factor. In MgB we observed the hardening of the phonon and the softening of phonon above and below the superconducting transition temperature, respsctively. This result suggests the relevant mechanisim of superconductivity in MgB is the electron–phonon interaction. From the precise measurement of the lattice constant, we found the negative thermal expansion at low temperatures in many correlated electron system. This negative thermal expansion can be explained by the Fermi liquid theory by Misawa.     

Thermophysical Properties of Molten Yttrium Measured by Non-contact Techniques

Understanding the nature and behavior of liquid metals requires accurate values of their physical properties (e.g., density, surface tension, viscosity). However, maintaining samples of matter in their liquid phases, in particular under supercooled conditions, is a great challenge when dealing with refractory metals. This is due mainly to their high melting temperatures (e.g., 3,695 K for W), their high vapor pressure, and the risk of melt contamination with a support or crucibles. Electrostatic levitation, laser heating in vacuum, and non-contact characterization techniques circumvented these difficulties and allowed the determination of the properties of several metals in their liquid state, above their melting temperature as well as in their supercooled phase. In this work, several thermophysical properties were successfully measured with an electrostatic levitation furnace under vacuum conditions. For the first time, density and viscosity data of yttrium were reported over large temperature intervals in the liquid phase. Over the 1,560 to 2,100 K temperature span, the density can be expressed as $\rho (T)=4.15\times 10^3-0.21\, (T - T_{\rm m})$ (kg·m^???3) with T _m = 1,796 K, yielding a volume expansion coefficient of 5.1 × 10^???5 K^???1. In addition, the surface tension can be expressed as $\sigma \left( T \right)=8.04\times 10^2-0.05\,(T - T_{\rm m})$ (mN·m^???1) and the viscosity as $\eta \left( T \right)=0.00287\,\exp \left[ {{1.1\times 10^5} \mathord{\left/ {\vphantom {{1.1\times 10^5} {\left( {\mbox{RT}} \right)}}} \right. \kern-0em} {\left( {\mbox{RT}} \right)}} \right]$ mPa·s over the 1,830 to 2,070 K interval. The results, in particular those for viscosity, suggest that performing similar experiments in microgravity could improve the accuracy of the measurements.     

Properties of Diffraction Grating Anomalies

Values provided by three different theories of the diffraction by gratings are compared with measurements made at millimetre wavelengths. The results based on the integral equation method of Pavageau and Bousquet give the best agreement with the experimentally-determined shapes of Wood anomalies. The wavelength dependence of P polarization anomalies is considered. Some properties of first-order P polarization resonance anomalies are demonstrated. The existence of second-order P resonances is shown. Second, third and fourth-order S polarization resonance anomalies have been found to occur for sinusoidal profile gratings at groove depths given by a simple formula. These anomalies cause large changes in grating efficiency to occur in very short wavelength intervals, and so might prove useful in spectroscopy.