A combined In situ grazing incidence small angle X-ray scattering and grazing incidence X-ray diffraction study of the growth of Ge Islands on pit-patterned Si(001) substrates

The growth of Ge islands on a pit-patterned Si(001) template is investigated in situ, combining grazing incidence diffraction, multiple wavelength anomalous diffraction, and small angle scattering. This allows monitoring in situ the detailed structural and morphological evolutions of the pits, of the wetting-layer and of the nucleated islands on the pit-patterned Si(001) substrate. It is shown that after Si regrowth, the Si substrate displays {107} and {1 1 11} facets. During the very first stages of Ge growth, the preliminary facets of the Si substrate are energetically unfavourable, and the pit facets break up into a rather complex pattern of {10n} and {11m} facets with n > 7 and m > 11. At 5 and 6 ML, intensity rods from {105} and {113}-type facets appear in the GISAXS images revealing the formation of pyramids and domes, respectively. The degree of ordering, the shape, strain and composition of the islands are characterized during the growth process to provide a detailed evolution of their structure and morphology.     

Reflectance of a wideband multilayer x-ray mirror at normal and grazing incidences

The reflectance of a W-B(4)C multilayer mirror, with a period thickness that increased with depth into the multilayer, was measured at near-normal incidence with synchrotron radiation and at grazing incidence with Cu Kα radiation. The period thickness increased linearly from 17.9 ? at the top of the multilayer structure to 21.9 ? at the substrate while the same ratio of nodal layer to period thickness was maintained. For a grazing angle of 80° (10° from normal incidence), the peak reflectance was 1.1% at a wavelength of 36 ?, and the reflectance profile was 1 ? wide. For Cu Kα radiation the reflectance peaked at a grazing angle of 2.4° and was 0.4° wide. Compared with a W-B(4)C multilayer mirror with a constant period thickness, the depth-graded multilayer mirror has wider reflectance profiles at near-normal and grazing incidences, resulting in larger integrated reflectances and wider fields of view.     

Grazing exit electron probe microanalysis for surface and particle analysis

We developed a new method of grazing exit electron probe microanalysis (GE-EPMA) and applied it to analyze both Si surfaces and Mg-salt particles. In conventional EPMA, X-rays are detected at an exit (takeoff) angle of approximately 45°. Therefore, when particles collected on a sample carrier are analyzed by EPMA, the X-rays from both the particles and the carrier are detected, although we need only the X-rays emitted from the particle itself. In contrast to this, the X-rays are detected at grazing exit angles in GE-EPMA. The X-rays emitted from deep inside of the sample are not detected under grazing exit conditions, and only X-rays emitted from the surface and the particle are measured. It was found that surface-sensitive analysis of a Si wafer was possible with low background at grazing exit angles. The intensity ratio of O Kα to Si Kα increased near zero degrees, indicating that the Si wafer is covered with a native Si oxide. Moreover, Mg Kα X-rays from a Mg-salt particle, which was deposited on the Si wafer, were detected with a small Si Kα intensity at grazing exit angles of less than 0.5°. By decreasing the exit angle to less than zero, only the top of the particle was observed; therefore, GE-EPMA measurement would make it possible to investigate the surface layer of one particle.     

Features of the transition radiation generated by weakly-relativistic electrons in the regime of grazing escape from a flat target

Features of the transition radiation (TR) generated in the vacuum ultraviolet range by weakly-relativistic electrons escaping from a target at small (grazing) angles have been theoretically studied. A significant (more than tenfold) increase in the angular density of TR with decreasing escape angle is predicted. It is established that the spectral and angular distribution of the TR intensity significantly depends on the target permittivity and the electron energy and escape angle.     

Azimuth dependence of Doppler spectra of sea clutter at low grazing angle

The effect of varying the azimuth angle of a cliff-top radar on the Doppler spectra of low grazing angle sea clutter has been investigated. The peak of the horizontally polarised Doppler spectra was found to depend on the component of the phase velocity of the breaking waves in the line of sight of the radar. The analysis was presented in terms of two main scattering components, one slow and one fast, which could explain the Doppler spectra as well as the higher moments of the spectra. The connection to the amplitude statistics for the two components was also discussed. The slow component was present all the time and had amplitude statistics that were Rayleigh-distributed. The fast component was present only intermittently and had amplitude statistics that were spikier than the Rayleigh distribution. The width of the spectra varied with azimuth in a way unrelated to the direction relative to the wind. A wave tank experiment with long wavelength mechanical waves and wind-generated waves illustrated that the cause of the broadening of the spectra was probably due to the effect of swell waves.     

金属表面氧化法表征高阻隔特性液晶聚合物膜的透氧性

利用原位掠入射X射线衍射(GIXRD)方法和显微观察法,研究了涂液晶聚合物膜的金属表面氧化腐蚀情况,根据金属表面的氧化速度计算了聚合物膜的氧气渗透性能。实验测得金属表面GIXRD衍射峰强度随氧化时间的延长不断减弱。在X射线入射深度内,利用显微镜原位观察得到了金属表面氧化物的面积,结合X射线能谱仪(EDS)测得的氧化物中氧含量,得到液晶聚合物膜的氧气渗透率在10-2cm3/(m2.d)数量级。     

Miniature Auger spectrometer with grazing incidence electron beam

The construction of a miniature Auger electron spectrometer is presented. The instrument is equipped with an electron gun of grazing incidence electrons and miniature retarding field analyser (RFA). Grazing electron beam of up to 3 keV as an excitation toll provides enhanced sensitivity to the top-most surface layer. Good energy resolution was achieved thanks to the aperture placed in the centre of curvature of the RFA. Combined with a normal electron beam spectrometer the system can provide valuable information about spatial distribution of atoms or molecules at probed surface layers. The example spectra obtained for a few substrate/adlayer systems measured by both grazing and normal electron beam spectrometers are presented. It is suggested that the differences in the relative signal amplitudes can answer the question which components are located at (or protrudes from) the top surface layer of the probed sample.     

Holographically recorded axicon for grazing incidence interferometry

Abstract

A diffractive axicon for grazing incidence interferometry of cylindrical objects is presented. For industrial measurement, an element with a diameter of 8 cm was manufactured. The axicon was recorded in dichromated gelatine (DCG) with a high-precision rotating stage. The diffraction theory for the design of the element is presented. The axicon was tested interferometrically. Some possible errors are discussed.     

Influence of SHI irradiation on the structure and surface topography of CdTe thin films on flexible substrate

Impact of ion irradiation on thin films is an emerging area for materials modification. CdTe thin films grown by thermal evaporation on flexible molybdenum (Mo) substrate were irradiated with Swift (100 MeV) Ag⁺⁷ ions for various ion fluence in the range 10¹²–10¹³ ions/cm². The modifications in the composition, structure and surface morphology have been studied as a function of ion fluence. The Energy Dispersive X-ray Analysis (EDS) shows slightly Te-rich composition for both as-grown and irradiated films with no significant change after irradiation. X-ray diffraction (XRD) analysis indicates a consistent shift in the (111) peak position towards higher diffraction angle and an increase in the full width at half maximum (FWHM) with increase in ion fluence. The change in the residual stress during irradiation has been evaluated and is related to the corresponding microstructural changes in the films. The initial tensile stress is found to be relaxed after irradiation. Atomic Force Microscopy (AFM) studies revealed significant grain splitting after irradiation and formation of hillocks at higher ion fluence. The surface roughness was significantly increased at higher ion fluence.     

基于单缝衍射原理的圆度误差测量方法

提出了一种全新的圆度误差光学自动测量方法.新方法基于单缝衍射原理,利用工件的圆度误差来改变衍射单缝的宽度,进而改变衍射条纹的间距.在测量单缝衍射中央明纹的宽度时,提出了用最小二乘法对测量到的衍射图像的光强分布进行二次曲线拟合,并由拟合得到的数学表达式,确定衍射暗条纹的精确位置.由导出的工件圆度误差与单缝衍射中央明纹宽度之间的关系,用最小二乘法对工件的圆度误差进行了评定.测量结果表明,新的圆度误差测量方法是可行的,圆度误差的相对不确定度小于1.4%,并且测量系统具有操作方便、精度高的优点,新方法也可应用于锥角、直线度误差等其它几何量的精密测量中.     

多种重离子辐照对硼硅酸盐玻璃机械性能的影响

研究辐照导致硼硅酸盐玻璃机械性能的影响, 对高放废物的长期安全处置具有重要的意义。本工作采用0.3 MeV的P离子、4 MeV的Kr离子、5 MeV的Xe离子以及8 MeV的Au离子分别辐照硼硅酸盐玻璃, 利用纳米压痕技术表征了辐照前后样品的硬度和模量。结果表明: 硼硅酸盐玻璃的硬度和模量在一定范围内会随着辐照剂量的增大而减小, 辐照达到0.1 dpa时硬度和模量变化趋于饱和, 此时硬度下降了35%, 模量下降了18%; 而且不同种类的离子辐照对硼硅酸盐玻璃的硬度和模量造成的变化趋势基本相同。使用掠入射X射线衍射仪对样品晶态结构进行了分析, 发现辐照后硼硅酸盐玻璃仍保持非晶状态。利用Raman光谱对辐照后样品的微观结构的变化进行了表征, 发现辐照会导致玻璃网络结构发生改变, 玻璃的聚合度下降, 无序度增加。本工作还证明了离子辐照导致玻璃机械性能变化的主要因素是离子在样品中的核能量沉积导致玻璃结构的改变。     

Fresnel diffraction at an opaque strip expressed by means of asymptotic representations of Fresnel integrals

The paper presents an asymptotic expression of relative intensity distribution in a Fresnel diffraction pattern at an opaque straight strip illuminated with a spherical wave. The asymptotic expression is used in an analysis showing an area of validity where the asymptotic expression reduces to an asymptotic expression of relative intensity distribution in a Fresnel diffraction at a half plane. The area of validity is defined through width of the geometrical shadow in a Fresnel diffraction pattern at an opaque straight strip and distance of a point under study to the center of the Fresnel diffraction pattern. Within this area, relative intensity in the Fresnel diffraction pattern at an opaque straight strip shows sinusoidal behavior, which can be used in easy location of maxima or minima of the relative intensity. The result of the analysis is supported by experiments realized in the area of validity and outside it.     

Decoherence in grazing scattering of fast H and He atoms from a LiF(001) surface

The influence of decoherence on the diffraction during grazing scattering of fast hydrogen and helium atoms from a LiF(001) single crystal surface with projectile energies of some keV, is investigated by two-dimensional angular distributions for scattered projectiles in coincidence with their energy loss and emitted electrons from the target surface. For keV hydrogen atoms, we identify the excitations of electrons and excitons of the target surface as the dominant mechanisms for decoherence, whereas for keV helium atoms these contributions are negligibly small. The suppression of electronic excitations owing to the band gap of insulators plays an essential role for preserving quantum coherence and thus for the application of fast atom diffraction as a surface analytical tool.     

Determination of Stress Tensors in thin textured copper films by grazing incidence diffraction

Ion-platted thin copper films were examined for residual stresses and texture by X-ray diffraction. The complete orientation distribution functions were determined and sharp (111)-fibre textures were found. The strains were measured by grazing incidence diffraction. The stress tensors were calculated using both texture-weighted elastic compliances and texture-independent X-ray elastic constants. The importance of the texture measurement for the stress tensor determination is discussed. The found stresses can be interpreted as thermally induced.     

偏压对直流磁控溅射Fe-N薄膜结构及性能的影响

为了揭示偏压对溅射态Fe-N薄膜磁学行为的影响规律及机理,采用直流磁控溅射工艺在不同偏压下制备了Fe-N薄膜.利用掠入射X射线衍射、小角X射线散射技术和振动样品磁强计研究了薄膜的相结构、厚度、表面粗糙度以及磁性能.结果表明,增加偏压有利于薄膜中非晶的形成,且随着偏压的增大,薄膜的厚度增加,表面粗糙度降低.Fe-N薄膜的磁性能表明,随着偏压的增加,薄膜的饱和磁化强度和矫顽力均有不同程度的减小.偏压的增加导致Fe-N薄膜由晶态向非晶态转变,从而引起磁性能的改变.     

Dependence on the sample width of signals from a near-field optical microscope

We numerically investigated signals from a scanning near-field optical microscope (NOM) for samples of various sizes by using the finite-difference time-domain method. Under the usual conditions that apply to detection, the signal intensity depends on the width of the sample, even though the sample will be wider than the wavelength, which is much larger than the aperture, i.e., the lateral resolution of the NOM. This is an obstacle to measuring the local optical constant of samples by means of obtaining the signal intensity. When waves propagating in all directions are collected, this dependence on the sample width is reduced. The whole angle detection is important for observing the distribution of the optical constants.     

Measurements of the Doppler spectra of breaking waves

A number of experiments have been carried out in two large wave tanks with three different radar systems. The radar frequency, grazing angle, azimuth angle, water wavelength, wave steepness and the breaking wave strength were all varied systematically. The velocity of the peak Doppler power spectral density was found to depend on the phase velocity of the breaking wave in the radar line of sight, but was independent of the radar frequency. The spectral width depended on the phase velocity of the wave, but not on the grazing angle used. The peak Doppler power and radar cross-section of the breaking waves was found to scale with the radar wavelength (proplambda_r ^1.5)     

掠流作用及不同穿孔角度时共振腔消声器性能分析

采用数值方法研究了掠流及不同穿孔角度下共振消声器声学性能的影响。通过求解三维非定常、湍流和不可压缩线性Navier-Stokes方程,得到掠流马赫数对不同穿孔角度下消声器传递损失的影响规律。结果发现,穿孔角度越小的消声器在对应马赫数下的共振频率偏移量越少,马赫数从0.05增加至0.1时,原模型与同向穿孔45°、60°、75°、逆向穿孔45°的偏移量分别为12.3%、9.2%、12.3%、20.0%和7.5%,同时同向穿孔的消声器较原模型在共振频率处都有较大的消声量,表明在流动状态下,穿孔角度显著影响消声器的消声性能,且同向穿孔能有效降低流动对消声器的影响。     

Investigation of buried quantum dots using grazing incidence X-ray diffraction

Self-organized, buried InAs quantum dots covered by an AlAs diffusion barrier were investigated under UHV conditions using grazing incidence X-ray diffraction. The experimental data is compared to the simulated results obtained by Finite Element Method and Distorted Wave Born Approximation. We have found that the simulated data could be compared to the experimental one only after convolution by the resolution element which can be estimated from the experiment. By adjusting the simulation parameters we were able to find good agreement between the simulated and the measured data.     

Fast, micrometer scale characterization of group-III nitrides with laboratory X-ray diffraction

We have designed a convergent beam, concurrent detection X-ray diffractometer. The instrument was built by Bruker AXS and is equipped with a rotating anode generator, a Johannson monochromator crystal for beam focusing, and a Soller slit arrangement in combination with a knife edge in front of the sample which defines the illuminated area on the sample. Samples up to 12 in. can be mounted on the sample stage of a D8 Eulerian cradle. A large area detector enables rapid simultaneous detection of the diffracted intensity. The instruments allow for a fast evaluation of large samples at high lateral resolution. In favourable cases lateral resolution down to 1 μm is possible. Furthermore a grazing incidence diffractometer has been developed which allows for depth-dependent measurements at high intensity.