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。     

Theoretical calculation of the angular distribution of radiation at the output of a flat nanodimensional X-ray waveguide

A model is proposed for theoretical calculations of the angular distribution of radiation intensity at the output of a flat X-ray waveguide representing an air-filled gap between two quartz plates. Good agreement between the theoretical and experimental angular profiles of CuK_α fluorescence intensity is obtained for planar waveguides with the gap widths ranging from 40 to 3000 nm. It is concluded that the Kirchhoff method can be applied to calculations of the spatial distribution of radiation intensity at the X-ray waveguide output.     

X射线反射法分析ZnO基薄膜的厚度、密度和表面粗糙度

采用X射线反射法(XRR)测试了在SiO_2玻璃衬底上磁控溅射沉积的单层ZnO基薄膜的反射强度,得到了反射强度随掠入射角变化的曲线;讨论了薄膜厚度、密度和表面粗糙度与反射曲线的关系,最后通过拟合XRR曲线获得了所制备薄膜的厚度、密度和表面粗糙度分别为55.8 nm,5.5 g·cm~(-3)和1.7 nm,与利用XRR数据直接计算出的薄膜厚度56.2 nm仅相差0.4 nm,表面粗糙度也与AFM测试的结果基本相符。可见XRR能无损伤、精确且快速地测试薄膜试样的厚度、密度和表面粗糙度等参数。     

Characterization on pulsed laser deposited nanocrystalline ZnO thin films

Nanocrystalline zinc oxide thin films were deposited on glass and silicon substrates by using pulsed laser deposition at different laser energy densities (1.5, 2, and 3 J/cm²). The film thickness, surface roughness, composition, optical and structural properties of the deposited films were studied using an α-step surface profilometer, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), optical transmittance, and X-ray diffraction (XRD), respectively. The film thickness was calculated as 244 nm. AFM analysis shows that the root-mean-square roughness increases with increasing laser energy density. XPS analysis shows that the interaction of zinc with oxygen atoms is greatly increased at high laser energy density. In the optical transmittance spectra, a shift of the absorption edge towards higher wavelength region confirms that the optical band gap increases with an increase in laser energy density. The particle size of the deposited films was measured by XRD, it is found to be in the range from 7.87 to 11.81 nm. It reveals that the particle size increases with an increase in laser energy density.     

Instrument-invariant method of film thickness determination by means of substrate-to-film X-ray peak intensity ratioing

A simple method for the determination of thin film thickness using X-ray spectrometry is described. The ratio of the substrate X-ray peak intensity to that of the film is taken as a measure of the thickness of the film. A calibration curve, constructed using specimens of known thickness, can then be used for thockness determination. The results are independent of the incident electron beam current. The calibration curve is made instrument invariant by means of a normalization procedure and by taking into account the respective X-ray take-off angles. Normalized calibration curves are reported for 13 different elements on a silicon substrate, covering thicknesses between 2.5 and 650 nm. The method, ideally suited to thin films on solid substrates, can also be applied to films not on substrates, and in the presence of a thin organic interfacial layer between film and substrate.     

Surface strains and measurements of misfit dislocation density by diffraction methods in thin films on substrates

In-plane strain variations near the free surface of an epitaxial thin film containing misfit dislocation shave been calculated. It is shown that strain distribution under the surface of the film is not constant and this distribution also depends on film thickness even for constant misfit dislocation density. The strain derived from diffraction measurements must therefore be corrected to obtain the true misfit dislocation density.     

Elastic strain and misfit dislocation density in Si0.92Ge0.08 films on silicon substrates

Thin (less than 1 μm) epitaxial Si_0.92Ge_0.08 films on (100) Si substrates were grown by an UHV evaporation technique at a substrate temperature of 750 °C. The film strain and misfit dislocation density were examined by means of X-ray diffraction and transmission electron microscopy, respectively. The films are shown to be in state of compression, and the misfit dislocation density depends strongly on film thickness. The critical film thickness below which pseudomorphic growth without misfit dislocations occurs is found to be about 0.1 μm. The extrapolation model of van der Merwe's misfit dislocation theory is modified assuming low lattice mismatch and a diamond structure. The misfit dislocation distances thus calculated are compared with the measured distances, and it is found that the former are always smaller than the latter.     

Statistical modelling of predicted non‐stationary vehicle vibrations

This paper describes a method to predict the vertical vibrations of road vehicles from measured pavement profiles. It discusses the limitations of current methods used for analysing and simulating vehicle vibrations and shows that more accurate characterization and simulation of the transport environment must take into account the non‐stationary nature of road vehicle vibrations. Vertical vibrations for typical transport vehicles under various operating conditions and pavement profiles are predicted using a computer model of the vehicle characteristics and analysed to produce the spectral and statistical characteristics. The paper also presents an improved method to compute the vibration intensity by using a dynamic segmentation data reduction technique. The effectiveness of the procedure to characterize the non‐stationarity of random vehicle vibrations is demonstrated. Finally, the paper deals with the statistical distribution of the vibration intensity and demonstrates how it can be adapted to a technique for the simulation the non‐stationary nature of random vehicle vibrations. Copyright © 2002 John Wiley & Sons, Ltd.     

High energy xenon ion beam assisted deposition of TiN film and its industrial application

TiN films have been synthesized by ion beam assisted deposition employing xenon ions with an energy of 40 keV. The formed TiN films were investigated systematically in respect of surface morphology, composition, structure and mechanical properties. Then, they were applied to surface protection of scoring dies. Atomic force microscopy and interferometric observation showed that the TiN film is relatively smooth. Rutherford backscattering spectroscopy analysis indicated that few xenon atoms are retained in the film. It was found by transmission electron microscopy and X-ray diffraction experiments that the formed TiN is a nanocrystal (< 10 nm) film and exhibits slightly (200) preferred orientation. An ultra low load microhardness indentor system was used to examine the plastic property of the film and a hardness of 2300 kgf mm^–2 was calculated from the measured data. Scratch tests showed that the adhesion of TiN film deposited by ion beam assisted deposition at ambient temperature is superior to that of high temperature physical vapour deposited (PVD) TiN film. Both a pin-on-dick tribotest and SRV wear test revealed that the wear resistance of the specimen can be greatly improved by TiN coating. A five times increase of service life of different scoring dies could be obtained by protection of TiN coating.     

Improved Contact X-Ray Microradiographic Method to Measure Mineral Density of Hard Dental Tissues

Contact X-ray microradiography is the current gold standard for measuring mineral densities of partially demineralized tooth specimens. The X-ray sensitive film specified in the last J Res NIST publication on the subject is no longer commercially available. OBJECTIVES: Develop a new microradiographic method by identifying a commercially available film with greater than 3000 lines per millimeter resolution, which is sensitive to X rays, and develop correct film processing for X-ray microradiographic application. METHODS: A holographic film was identified as a potential replacement film. Proper exposure was determined utilizing a thick nickel plate to create test-strips. Film development was bracketed around manufacturer suggestions. Film linearity was determined with aluminum step-wedges. Microradiographs of 100 μm thick tooth sections, before and after acidic challenges, were a final test for film. Magnified images were captured with a digital microscope camera with 0.305 micrometers per pixel resolution. RESULTS: The appropriate film exposure was 30 minutes at 80 kV(p) and 3 mA with a development time of 2 minutes. Step-wedge experiments show the system to be linear in terms of pixel intensities with respect to x-ray attenuation for normalized pixel intensity values that are 10% to 90% of full scale (r(2) = 0.997) which encompasses the full exposure region of tooth tissue. Enamel sections were analyzed and show distinctive differences between erosion and demineralization. The image capture device resolution of 0.305 micrometers per pixel limits the system resolution. CONCLUSION: Use of the identified holographic film when combined with the described processing modifications has resulted in an improved X-ray microradiographic method for the measurement of mineral density of dental hard tissues. The method described can be further improved by using a higher resolution digitization system. The method is appropriate for quantitatively measuring changes in mineral density and erosion.     

Crystalline structure of germanium films on silicon substrates: I. Investigation of the perfection of germanium heteroepitaxial films on silicon by X-ray diffraction methods

The purpose of this paper is to describe an investigation of the structural perfection of heteroepitaxial Ge films on silicon by different X-ray diffraction methods. Quantitative information about the degree of structural perfection of the films has been obtained by X-ray intensity jumps measured near the K-edge absorption of germanium and by rocking curves. Structural damage in the films and substrates has been studied by X-ray topographical methods. The possibility of obtaining independent film and substrate topograms has been shown. Elastic strains arising during the film growth lead to film and substrate fragmentation. Films and substrates have the same configuration and sizes of fragments. A new X-ray method for the heteroepitaxial films thickness measurement has been proposed.     

Intensity profiles along the RHEED streaks for various thin film surface morphologies

Intensity distribution profiles of reflection high energy electron diffraction (RHEED) along the (00) and (01) reciprocal rods are calculated as a function of the grain width, the height difference between neighbouring grains (intergrain roughness), and the surface roughness of the individual grain (intragrain roughness). The calculations include the refraction and the absorption of electron beams and the shadowing effect by the neighbouring grains. The calculations show that the major intensity moves from the three-dimensional (3D) Bragg diffraction to the specular beam as the grain width increases and that a remarkable change in the intensity profiles occurs when the grain width becomes comparable with the decay length of the electron beam in the film. Not only the growth of 3D Bragg peaks but also shifts of the peak positions, induced by the increase of the intra- and intergrain roughness, are simulated. The calculated spectra are compared with the experimental intensity profiles along the streaks measured together with a RHEED intensity oscillation during a homoepitaxy of Ag films.     

Berechnung des (420)-Reflexprofiles einer γ′-Fe4N1−x-Schicht mit Säulenstruktur und Dehnungsrelaxation

Calculation of the (420)-reflection profile of a γ′-Fe₄N_1?x layer with columnar structure and strain relaxation A couple of surface treatments and thin film deposition methods lead to strained layers and columnar layer structure. Within the columns strain relaxation outwards along the column radius occurs. This relaxation causes asymmetrical broadening of X-ray reflections. A method is introduced, to calculate the reflection profiles of layers with columnar structure and strain relaxation. The possibility of a comparison between a calculated and a measured profile for the determination of the average column radius and the relaxation is discussed.     

A new semi-analytical method analyzing the magnetic field in unbalanced magnetron sputtering system

A new method, semi-analytical method (SAM), is first applied to calculate and analyze the magnetic filed in unbalanced magnetron sputtering system, and introduced in detail. An analytic solution of the scalar magnetic potential in the system can be acquired by the SAM. Its unknown number is much less than that in the numerical method. The analytic series expression of magnetic flux density can be easily obtained directly by differentiating the scalar magnetic potential function, and it can also easily ensure the precision of solving the magnetic flux density. The comparison of results between the values measured by experiment and the values calculated by the SAM has shown correctness and effectiveness of this method. The SAM cannot only accurately describe the distribution of magnetic flux density and optimize magnetic field in unbalanced magnetron sputtering system, but also be conveniently used for the simulation about plasma distribution and thin film growth.     

An intensity correction for pole figure measurements by grazing incident and grazing exit angle X-ray diffraction

In pole figure measurement by X-ray diffraction, the intensity must be corrected for geometric factors entering into the intensity. For the grazing (often, also called glancing) angle diffraction mode, the irradiated area changes with the grazing angle. A theoretical analysis of this effect was made and compared with measured data from a texture-free silver sample. An intensity correction factor is given as the ratio of the detector slit width and the width of the irradiated sample area as seen from the detector. As an application, the texture of thin copper film was studied.     

Experimental evaluation of a new expression for the far field of a diode laser beam

The validity of a newly derived expression for the far field of a diode laser beam is examined by comparison of the measured intensity profiles with the calculated ones for typical double-heterostructure diodes. I also clarify which of the new and conventional expressions for the intensity profiles in the plane normal to the junction is more useful. The cause of the observed discrepancy between the measured and calculated profiles in the plane parallel to the junction is investigated by consideration of the higher-order Hermite-Gaussian modes. Further, I examine how the axial intensity varies with the propagation distance.     

Photonic-Band Structures in Macroporous Silicon

Macroporous Si was prepared by electrochemical etching at a linearly varying applied voltage. A relationship between the process parameters (illumination intensity, current density, and applied voltage) was derived in a diffusion–drift model. The experimental dependences of the ratio of the photohole concentration to the current density on the distance between the illuminated surface and pore bottom were shown to agree with the diffusion–drift model for nonequilibrium-hole transport provided that the anode thickness exceeds the diffusion length of holes and the pore radius is comparatively large. The photonic band gap of the two-dimensional macroporous Si structure was calculated by the plane-wave method. The transmittance of macroporous Si was measured. The effect of surface recombination on the lifetime of nonequilibrium charge carriers was assessed.     

Problems in the Determination of Internal Stresses in Plasma Assisted CVD TiN Films

The measurement of internal stresses in a PACVD TiN film proved experimentally to be difficult bya conventional X-ray diffraction technique.The linear relationship between 2θ and sin~2(?) couldhardly be reached in some cases.Nevertheless.a good confirmation between the variation ofFWHM-sin~2(?) and 20-sin~2(?) was revealed for every nonlinear forms.It followed that the effect ofnondistributed micro-strains might exist in plasma assisted vapor deposited films,which usuallyhave a strong crystal orientation,and the method of effectively separating macro-stress andmicro-strain must be applied for the precise determination of internal stresses in PACVD films.     

衍射频谱法测光栅膜层厚度

根据傅立叶光学理论从光栅的衍射频谱中可以反推光栅本身的多种信息,包括其形貌特征。 利用矩形相位光栅的傅立叶变换,推导出零级和一级衍射光强和矩形相位光栅膜层厚度之间的函数关系,据此可在测得零级和一级次光强后,推算出光栅膜层厚度。以台阶仪作为标准,该方法的测量误差在4%以内。     

The properties of samarium doped ceria oxide thin films grown by e-beam deposition technique

One of the main challenges in today's solid oxide fuel cell (SOFC) technology is the reduction of their operating temperature. New types of oxygen ion conducting materials are currently under investigation to overcome the problems which SOFC faces at high temperatures. Samarium doped ceria oxide (SDC) was the material of investigation in this work. Optical quartz (SiO₂) and Fe–Ni–Cr alloy (Alloy 600) were the two types of chosen substrates onto which SDC thin films were deposited by e-beam evaporation technique. The bias voltage was applied to the substrate during film growth. It had an influence on film formation, its microstructure and density because of the ionized particles presence in the SDC vapor stream. Changes in crystallite size and surface morphology were determined from X-ray diffraction data and scanning electron microscopy images. Influence of bias voltage on porosity of formed SDC thin films on optical quartz were calculated from transmittance spectra data by using Swanepoel method. The porosity decreases up to 12% by decreasing bias voltage from 0 to ?150 V.