Structural investigation of thin tetracene films on flexible substrate by synchrotron X-ray diffraction

Structural properties of tetracene thin films grown by vacuum sublimation on a flexible Mylar^© substrate have been investigated by means of synchrotron X-ray diffraction. The films are polycrystalline and are made up of crystalline domains oriented with the (0 0 l) planes almost parallel to the substrate and completely misoriented around the surface normal. Two crystallographic phases (α and β thin film phases) have been identified. They differ for the d_h k l interplanar spacing, both larger than that of the bulk. As a comparison, results from tetracene films grown on SiO₂ have been reported to investigate the different charge transport properties of films grown on Mylar and on SiO₂ substrates.     

High resolution X-ray diffraction investigation of epitaxially grown SrTiO3 thin films by laser-MBE

SrTiO3 thin films are epitaxially grown on DyScO3, LaAlO3 substrates with/without buffer layers of DyScO3 and SrRuO3 using laser-MBE. X-ray diffraction methods, such as high resolution X-ray diffraction, grazing incident X-ray diffraction, and reciprocal space mapping are used to investigate the lattice structure, dislocation density, in-plane lattice strain distribution along film thickness. From the measurement results, the effects of substrate on film lattice quality and microstructure are discussed.     

一维Co单晶纳米线的x射线研究

对电化学沉积法在多孔氧化铝中制备的一维单晶Co纳米线阵列的结构和形态利用各种x射线衍射测量方法进行了细致的表征.确定了阵列中的纳米线在线长方向均为一致的晶体学取向，并以很高的平行度排列.并且发现生长条件可能在一维纳米线中引起不同程度的螺旋晶格曲扭.根据实验观察结果提出了一个具有手性的螺旋曲扭模型.利用超导量子干涉磁强计测量了样品在300K下的磁特性，分析发现螺旋扭曲可以在相当大的程度上改变纳米线阵列的各向异性.说明利用磁弹性效应有可能有效地调节纳米线的磁各向异性. 关键词： 纳米线 单晶 x射线摇摆曲线 x射线极图     

基于X射线衍射的GaN薄膜厚度的精确测量

结合Williamson-Hall plot方法和线型分析方法的优点,提出了一种有效分离有限晶粒尺寸和非均匀应力等X射线衍射展宽效应的方法,可以用于GaN外延层厚度等参数的快速精确测量.用该方法对一系列在蓝宝石衬底上生长的厚度在0.7—4.2μm的GaN外延膜进行了测量,并与椭圆偏振光谱法测量结果进行了比较,结果表明其差别<4%,反应了这种方法的准确性. 关键词： GaN薄膜 厚度测量 X射线衍射     

ESR and X-ray diffraction studies of the CVD diamond films

Thin polycrystalline, diamond films were prepared by thermal decomposition of hydrocarbon and hydrogen in the presence of a hot tungsten filament (HF CVD technique). Electron Spin Resonance (ESR) spectroscopy investigations were carried out and correlated to diamond microcrystal size estimated on the basis of X-ray diffraction (XRD) measurements. It was shown that both ESR signal and average crystal size of the thin CVD diamond films depend strongly on the ratio of hydrocarbon/hydrogen concentrations in the CVD reactor. XRD spectra indicate the presence of fullerence and, graphitic polytypes in most studied samples, independent of growth conditions. Observed reciprocal proportionality of the ESR signal intensity versus diamond grain size suggests that the above mentioned carbon phases are mainly dispersed at the grain boundaries.     

Correlation between density and structure. in boron nitride thin films by X-ray diffraction

* _ion=100 eV. Above E^* _ion the average density (deduced from X-ray reflectivity) shows a strong increase, indicating the sudden appearance of the cubic boron nitride phase consistent with the sp³ concentration deduced from IR absorption spectroscopy. The in-plane X-ray diffraction shows that this cubic phase consists of small nanocrystals of 70 Å linear size. Received: 26 November 1996/Accepted: 27 January 1997     

X-ray photoelectron diffraction study of ultrathin PbTiO3 films

Full hemispherical X-ray photoelectron diffraction (XPD) experiments have been performed to investigate at the atomic level ultrathin epitaxial c-axis oriented PbTiO₃ (PTO) films grown on Nb-doped SrTiO₃ substrates. Comparison between experiment and theory allows us to identify a preferential ferroelectric polarization state in a 60 ? -thick PTO film. Multiple scattering theory based on a cluster-model [ Phys. Rev. B , 075404 (2001)] is used to simulate the experiments.     

X-ray diffraction imaging investigation of silicon carbide on insulator structures

A new process was recently developed to manufacture silicon carbide on insulator structures (SiCOI). The process consists of several steps: (i) hydrogen implantation into an oxidised SiC wafer, (ii) bonding the oxidised surface of this wafer to an oxidised silicon substrate and (iii) high temperature splitting of a thin SiC film from the SiC wafer at the depth of the maximum hydrogen concentration and further annealing of the splitted film. The defect generation occurring during this process was investigated by synchrotron radiation X-ray diffraction topography, with special emphasis on to the last two steps. Various X-ray topographic techniques were used to characterise the lattice defects inside the SiC wafer, to quantify the strong lattice distortion near the edges of the splitted SiC film and to reveal SiC film regions lost during the splitting process. Moreover, we show that the strain fields of dislocations, observed in the silicon substrate after high temperature splitting and annealing of the splitted structure, induce a corresponding deformation in the thin SiC overlayer, despite the presence of the sandwiched oxide film. The defect density is much lower in the central region of the SiCOI structure. Received: 29 June 2001 / Accepted: 8 November 2001 / Published online: 20 March 2002     

Be薄膜应力的X射线掠入射侧倾法分析

由于铍薄膜极易被X射线穿透, 传统的几何模式下很难获得有效的X射线衍射应力分析结果. 本文采用掠入射侧倾法分析SiO₂基底上Be薄膜残余应力, 相比其他衍射几何方法, 提高了衍射的信噪比, 获得的薄膜应力拟合曲线线形较好. 对Be薄膜的不同晶面分析, 残余应力结果相同, 表明其力学性质各向同性; 利用不同掠入射角下X射线的穿透深度不同, 获得应力在深度方向上的分布; 由薄膜面内不同方向的残余应力相同, 确定薄膜处于等双轴应力状态. 关键词： Be薄膜 X射线衍射 应力     

Temperature dependent structure of spider silk by X-ray diffraction

We have investigated the structure of spider dragline silk by X-ray diffraction over a broad temperature range from room temperature up to thermal denaturation conditions. The dominating signal from the β-sheet crystallites is analyzed. Pronounced changes of scattering intensity starting at temperatures around 150 °C are observed. These changes are discussed in view of the respective lattice constants, crystal size, size distribution, crystallite number density and amino acid composition. PACS 87.68.+z; 87.15.-v; 87.64.Bx     

Investigating stacking faults in nonpolar gallium nitride films using X-ray diffraction

Nonpolar (11-20) GaN films with different basal-plane stacking fault (BSF) densities (determined using transmission electron microscopy) were investigated using X-ray diffraction. Diffuse streaking from I₁ and I₂ BSFs was observed in reciprocal space maps of the 10-10 and 20-20 reflections. X-ray calibration curves for BSF density determination can be plotted using the diffusely scattered intensity of open detector 10-10 or 20-20 ω-scans measured at a fixed, large separation from the peak maximum. However, ab initio determination of stacking fault densities is not possible due to additional broadening from other defects. Similarly, ω-scan peak widths are poor indicators of BSF densities.     

Residual stress/strain analysis in thin films by X-ray diffraction

Residual stresses are found in the majority of multilayer thin film structures used in modem technology. The measurement and modeling of such stress fields and the elucidation of their effects on structural reliability and device operation have been a “growth area” in the literature, with contributions from authors in various scientific and engineering disciplines.

In this article the measurement of the residual stresses in thin film structures with X-ray diffraction techniques is reviewed and the interpretation of such data and their relationship to mechanical reliability concerns are discussed.     

Epitaxial growth and X-ray diffraction analysis of single-crystal thin films of CuCl

The epitaxial growth of single-crystal thin films of cuprous chloride (CuCl) with 2 to 4-μm thicknesses is reported for the first time. Single-crystal structure is achieved by thermal deposition of CuCl onto a sodium chloride (NaCl) substrate whose space lattice and lattice constant match that of CuCl. X-ray diffraction analysis reveals single-crystal structure of these CuCl thin films. Luminescence spectra arising from the decay of excitonic molecules to exciton states are substantially narrower in the single crystal thin films compared with polycrystalline thin films grown on amorphous substrates.     

Structural and optical characterization of the propolis films

We have performed structural and optical characterizations of the propolis (an organic entity of biological nature) films grown on various non-organic substrates. The films were grown from a propolis melt or a propolis alcohol solution. The crystal structure has been observed in the films precipitated from the solution onto substrates such as an amorphous glass and sapphire or semiconductor indium monoselenide. For any growth method, the propolis film is a semiconductor with the bandgap of 3.07 eV at 300 K that is confirmed by a maximum in photoluminescence spectra at 2.86 eV. We argue that propolis films might be used in various optoelectronic device applications.     

X-ray diffraction and IR spectroscopy investigation of synthesized and biogenic nanocrystalline hydroxyapatite

The results of the X-ray diffraction analysis (XRD) and optical (IR) investigations of hydroxyapatite (HAP) produced from the egg-shell of birds and biogenic HAP (a slice of tooth enamel) are presented. The synthesized material is a nanocrystalline hydroxyapatite with an average crystal size ∼35 nm. The outer and inner sides of the tooth enamel slice include HAPs with a different structural organization. The inner side of the tooth slice containing HAP nanocrystals, with an average size of ∼15 nm, demonstrates the most similarity with the synthesized material. Hydroxyapatite of the outer enamel consists of hydroxyapatite with a strong texture organization whose common elements, namely hexagonal prisms, are predominantly oriented along the [001] crystallographic direction. The IR spectra of the tooth enamel (in addition to fundamental HAP vibration modes) revealed the vibration modes of the collagen protein. The comparison of the characteristics of the synthesized and biogenic HAP show that synthesized HAP is a promising candidate for medical applications, e.g., for improving the adhesion properties of dental cement pastes.     

X-ray diffraction investigation of the hexagonal-fcc structural transition in yttrium trihydride under hydrostatic pressure

Pressure induced structural transition of yttrium hydride has been investigated using synchrotron radiation X-ray diffraction measurement up to 24 GPa at room temperature. A reversible hexagonal-fcc transition with a wide intermediate region from 11 to 20 GPa is confirmed, which is consistent with previously reported X-ray results. The diffraction patterns measured for the intermediate state are not interpreted in terms of a hexagonal-fcc coexisting state or as rare-earth structures with various metal-layer stacking sequences. The equation of state determined for the hexagonal-YH₃ provides a bulk modulus B₀ of 71.9 GPa, which is nearly half of the previously reported value, but is within the range of values reported for other rare-earth metal trihydrides with hexagonal structures.     

Inelastic light scattering and X-ray diffraction from thick free-standing porous silicon films

The results of Raman scattering and X-ray diffraction studies of thick, free-standing, porous Si layers with thickness up to 500 μm are presented. The Raman scattering spectra have a distinctive difference from previous data for porous Si films on Si substrate and for thin, free-standing, porous Si layers. The experimental data can be explained by a modified phonon confinement model that accounts for a comprehensive strained Si nanocrystal. The comprehensive strain is a tensile one, and the value of stress can be up to 3 GPa. This interpretation is supported by data of X-ray diffraction measurements.