Incident Angle X-ray Research Articles

Plane-wave synchrotron x-ray topography observation of grown-in microdefects in a slowly pulled CZ-silicon crystal

Plane-wave x-ray topography was used to characterize grown-in defects in silicon crystals grown by the Czochralski method at a slow speed. The 220 reflection rocking curves of the sample crystal were measured in a symmetric Laue case. Oscillatory profiles were clearly observed in the rocking curves and were in good agreement with those calculated from the dynamical theory of x-ray diffraction. Images of the grown-in defects were observed in the plane-wave x-ray topographs of the 220 reflection. The density of the defects was determined as 300 cm−3. The lattice strain around the defects was evaluated as 10−6 from the dependence of the defect image contrast on the x-ray incident angles. The defect images are discussed using a grown-in defect model of entangled dislocation loop clusters.

Effect of Au distribution in NiO/Au film on the ohmic contact formation to p-type GaN

The distribution of Au and NiO in NiO/Au ohmic contact on p-type GaN was investigated in this work. Au (5 nm) films were deposited on p-GaN substrates by magnetron sputtering. Some of the Au films were preheated in N2 ambient to agglomerate into semi-connected structure (abbreviated by agg-Au); others were not preheated and remained the continuous (abbreviated by cont-Au). A NiO film (5 nm) was deposited on both types of samples, and all samples were subsequently annealed in N2 ambient at the temperatures ranging from 100 to 500 °C. The surface morphology, phases, and cross-sectional microstructure were investigated by scanning electron microscopy, glancing incident angle x-ray diffraction, and transmission electron microscopy. I-V measurement on the contacts indicates that only the 400 °C annealed NiO/cont-Au/p-GaN sample exhibits ohmic behavior and its specific contact resistance (ρc) is 8.93 × 10−3 Ω cm2. After annealing, Au and NiO contact to GaN individually in the NiO/agg-Au/p-GaN system while the Au and NiO layers become tangled in the NiO/cont-Au/p-GaN system. As a result, the highly tangled NiO-Au structure shall be the key to achieve the ohmic behavior for NiO/cont-Au/p-GaN system.

NEXAFS study of amino acid analogues assembled on gold

In this work, near-edge x-ray absorption fine structure spectroscopy (NEXAFS) experiment is done to obtain the chemical and structural information about the occurrence and the average orientation of unoccupied molecular orbitals within the organic films. Amino acid, such as Tyrosine and 3,4-dihydroxyphenylalanine (DOPA), is linked to a thiol through a peptide bond and is adsorbed and self-assembled to polycrystalline gold surfaces. Results from the C k-edge and O k-edge spectra serves as fingerprints to each amino acid analogues. The average orientation of the molecules relative to the gold surface is determined from the polarization effects observed as intensity changes of the peaks in the spectra when the x-ray incidence angle is varied. It is assumed that the average tilt angle of the main molecular axis of amino acid linked to short amidethiol is based on the deduced orientation of the peptide bond.

Fabrication and properties of the Y-doped Al2O3 high-k gate dielectric films

Y-doped Al2O3 dielectric films have been fabricated by reactive radio frequency co-sputtering method. Grazing angle incidence x-ray diffraction results show that the as-deposited and annealed films are amorphous. High resolution scanning electron microscope and atomic force microscope have been applied to observe the cross-section and the surface morphology of the thin films. The electric C-V and I-V characteristics were measured at high and variable frequency, respectively. It was found that the dielectric constant k of the films increases remarkably (from 8.14 to 11.8) with increasing Y-doping concentration. The Y—O bond is stronger than Al—O due to the obvious difference in electro-negativity between the two bond members, which enhanced the ionic polarization in the thin films leading to an increase of the dielectric constant. It was supposed that the presence of Y ions changed the structure and atomic coordination of Al2O3. The films were very smooth which meet the requirements of the device.

Structural, Electrical and Optical Characterization of SrIrO<SUB>3</SUB> Thin Films Prepared by Laser-Ablation

SrIrO3 thin films were prepared by laser ablating a monoclinic SrIrO3 target at the substrate temperature of 973 K with oxygen pressure ranging from 4 to 67 Pa. The glancing angle incidence X-ray diffraction (GIXRD) and micro-X-ray photoelectron spectroscopy (XPS) results suggested that SrIrO3 thin films were obtained. The resistivities and transmittance of SrIrO3 thin films at room temperature were in the range from 0.93 to 4.8×10−5 Ωm and from 0.20 to 0.30 in the wavelength range of 600–800 nm, respectively. The electrical property of SrIrO3 thin films changed from semiconductive to metallic with increasing the ablation oxygen pressure.

High-temperature self-grown ZrO2 layer against Cu diffusion at Cu(2.5at.%Zr)∕SiO2 interface

Films of pure Cu and of Cu alloy containing 2.5at.% of Zr [abbreviated as Cu(2.5at.%Zr)] were deposited on SiO2∕Si substrates by magnetron sputtering. Samples were subsequently annealed at temperatures ranging from 500to800°C in vacuum (2×10−5Torr) for 30min and analyzed by Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and glancing incident angle x-ray diffraction. Resistivity of both pure Cu and Cu alloy films, before and after annealing, was measured at room temperature by using a standard four-point probe technique. Upon annealing, the added Zr atoms in Cu(2.5at.%Zr) diffuse to both the free surface and the alloy∕SiO2 interface and react with the residual oxygen in the vacuum system and with the SiO2 to form a ZrO2 layer. At the interface, a self-grown ZrO2 layer forms upon annealing at 700°C that hinders Cu from diffusion into the SiO2, while Cu diffusion into SiO2 is apparent for pure Cu on SiO2 at this temperature. The room-temperature resistivity of the as-deposited Cu(2.5at.%Zr) film is 21.8μΩcm and decreases to about 6.2μΩcm upon vacuum annealing at 700°C for 30min. This value is still thrice that of the pure Cu film similarly treated. The relation between the diffusion of the added Zr and the characteristics of Cu(2.5at.%Zr)∕SiO2 interface, self-formed surface layer, and the resistivity change, is discussed.

Epitaxial Growth of (001)ZrN Thin Films on (001)Si by Low Temperature Process

We have prepared (001)ZrN films epitaxially grown on (001)Si substrates by a low temperature process using an ultrahigh vacuum magnetron sputtering system, and evaluated their epitaxial relationships and film qualities, using X-ray diffraction (XRD) analysis, X-ray pole figure, grazing incidence angle X-ray reflectivity (GIXR), transmission electron microscopy (TEM) and atomic force microscopy (AFM). It is clarified that (001)ZrN films grow epitaxially on (001)Si even at room temperature with the directional relationship of ZrN(001)[110]∥Si(001)[110], and the lattice mismatch at the interface between (001)ZrN and (001)Si is relaxed due to the existence of a very thin transition layer. It is also revealed from GIXR and AFM that the epitaxial ZrN films have a high film density and a flat surface morphology, irrespective of substrate temperature.

Failure Mechanism of Amorphous and Crystalline Ta-N Films in the Cu / Ta ­ N / Ta / SiO2 Structure

The diffusion barrier properties of as-deposited amorphous and crystalline TaN between Cu and have been investigated in structures. The thermal reactions of and after annealing in vacuum at 500 to 900°C were investigated by using sheet resistance measurements, glancing incident angle X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, and Rutherford backscattering spectrometry. No significant reaction and change of sheet resistance were detected for both systems after annealing up to 800°C. As compared to TaN, exhibited better electrical properties and capability for preventing Cu diffusing through it. However, the sheet resistance of both systems increased abruptly after annealing at 900°C, especially the system. The severe increase in sheet resistance corresponds to the deterioration of Cu surfaces. Broken holes were seen in the layer, which were the initial sites for the structural failure. The cause of failure in stacks is discussed on the basis of the characteristics of Ta-N films upon heat-treatment. © 2004 The Electrochemical Society. All rights reserved.

Effect of in situ CdCl2 treatment on spray deposited CdTe∕CdS heterostructure

CdTe thin films have been deposited without and with in situ CdCl2 treatment using spray pyrolysis technique. Scanning electron microscopy studies show enhanced grain growth in the presence of CdCl2. Glancing incidence angle x-ray diffraction is used to observe the microstructural changes of CdTe∕CdS heterostructure at different depths by changing the incident angle. Spraying of CdCl2 on CdS prior to CdTe deposition promotes S diffusion throughout CdTe film and also Te diffusion into CdS. There is an associated change in the microstress of the CdTe film at different layers. The films without CdCl2 treatment show compressive microstress varying from −98to−158MPa with increasing incident angle. CdCl2 spray during CdTe deposition leads to compressive microstress varying from −98MPa at the interface to −19MPa near the surface and CdCl2 spray prior to CdTe deposition leads to a mildly tensile stress (+20to+40MPa). Photoluminescence spectra for CdTe films with the in situ treatment show a reduction in the band gap due to S diffusion as well as the reduction in the defect band intensity. An in situ CdCl2 treatment results in less surface oxidation compared to ex situ process, as seen from x-ray photoelectron spectroscopy study. A shift of ∼200meV in the Fermi energy towards the valence band is also observed in valence band spectra after the in situ CdCl2 treatment.

Photoelectron escape from iron oxide

Iron oxide of nanometer thickness were grown in situ by step-by-step oxidation of an iron foil to measure the escape probabilities of O 1s photoelectrons as a function of depth of origin, the so-called emission depth distribution function (EDDF), and the mean escape depth (MED). To record photoelectron spectra for a wide range of emission angles, the X-ray excitation source was positioned on the opposite side of the iron foil with respect to the analyzer. To excite photoelectrons on the side of the foil surface adjacent to the analyzer, the foil was made thin enough to be semitransparent to the X-ray radiation. The O 1s spectra were recorded for a wide range of oxide thicknesses until no features of metallic iron were recognized in the photoelectron spectra. The escape probability of the O 1s photoelectrons in the iron oxide was derived from the oxide-thickness dependence of the O 1s peak areas. The resulting EDDF reached a maximum beneath the oxide surface for X-ray incidence and electron-emission angles located along the surface normal. For the same incidence angle and an emission angle of 60°, the escape probability could be well approximated by a simple exponential function. The mean escape depths were obtained for both experimental geometries and agreed well with the available theory.

Material characterization and nanohardness measurement of nanostructured Ta–Si–N film

This paper presents a study of the relation between the process, composition and nanohardness of the nanostructured Ta–Si–N films that have been applied in an IC diffusion barrier or mechanical coating. Ta–Si–N films are reactively cosputtered by individual Ta and Si targets in a N 2/Ar gas. They are characterized by Rutherford Backscattering Spectroscopy (RBS), grazing incident-angle X-ray diffractometer (GIAXRD) and nanoindenter for the composition, structure and nanohardness analysis, respectively. Increasing Si target power or decreasing Ta target power will produce higher Si/Ta composition ratio in Ta–Si–N films with higher amorphous content as well as smaller nanocrystalline grains. The nanohardness of Ta–Si–N films measured by nanoindentation is between 13.5 and 16.4 GPa. Increasing N 2 flow reduces the nanohardness while the grain size of Ta–Si–N film increases slightly. However, increasing Si composition reduces both grain size and nanohardness of Ta–Si–N films.

Electro-Optical Properties and Structures of (Pb, La)(Zr, Ti)O3 and PbTiO3 Films Prepared Using Aerosol Deposition Method

The electro-optical (EO) properties, film structures and far-infrared spectra were measured for lanthanum-modified lead zirconate titanate [PLZT, Pb0.91La0.09(Zr0.65Ti0.35)O3] and lead titanate [PT, PbTiO3] films, prepared by the aerosol deposition (AD) method. The EO response appeared for AD films annealed at over 500°C, and increased as the annealing temperature increased. Downward shifts of the diffraction peaks, compared with diffraction peak positions of the corresponding to powders, were observed for as-deposited PLZT films in X-ray diffraction patterns of θ-2θ scans. The (200) peaks shifted to higher angles with increasing X-ray incidence angle to the film surface, indicating that the peak shifts were caused by lattice distortion induced by in-plane compressive stress. The (200) peaks shifted to the powder position when annealed at 600°C, which means that the annealing can relax the residual stress. Far-infrared spectroscopy measurements of reflectivity and transmittance were carried out on the PLZT and the PT powders and films, and the IR spectra of PT films were analyzed using the classical damped harmonic oscillator models to determine the oscillation parameters. We observed LO mode degradation and the broadening of the dielectric function peaks on the AD films. The frequencies of the E (1TO) soft-phonon mode of the annealed PT films were shown to have downward shifts of over 20 cm-1, compared with those of bulk ceramics and single crystals, suggesting that the AD may have induced a microscopic lattice degradation in the PT films, which may be responsible for the small EO response.

Wear behaviour of CrN coatings MEVVA ion implanted with Zr

CrN films deposited by a commercial physical vapour deposition (PVD) process were implanted with Zr ions by metal vapour vacuum arc (MEVVA) implantation at an energy of 40 keV and with doses ranging from 6×10 16 to 2×10 17 ion/cm 2. The films were characterised by glancing incident angle X-ray diffraction (GIXRD), optical microscopy and scanning electron microscopy (SEM). Friction and wear tests were carried out using a pin-on-disc tribometer with a 6 mm diameter ruby pin. X-ray photoelectron spectroscopy (XPS) results show the formation in the implanted zone (IZ) of ZrN/CrZrN. X-ray diffraction (XRD) shows evidence of crystal damage, which increases with dose. The post-deposition process has induced only small changes in the friction behaviour of the CrN film, and overall the tribological properties were not enhanced. Nano-hardness measurements show that implantation has caused softening of the IZ layer. The tribological behaviour is explained in view of these results.

Structural characterization of group III nitrides grown by pulsed laser deposition

We have grown thin GaN epitaxial films on Si(1 1 1) and sapphire (0 0 0 1) with AlN buffer layers using pulsed laser deposition and investigated the distortion of the films using synchrotron radiation grazing incidence-angle X-ray diffraction for the first time. We have found that the strains in the AlN films were almost fully relaxed at the growth temperature (800 °C) by the introduction of the misfit dislocations. However, we have also found that the introduction of misfit dislocations at the interfaces between the AlN buffer layers and the GaN films is not rigorous enough to release the stain fully at the growth temperature.

Depth profiling study of in situ CdCl 2 treated CdTe/CdS heterostructure with glancing angle incidence X-ray diffraction

CdTe thin films have been deposited using spray pyrolysis technique without and with in situ CdCl 2 treatment. Scanning electron microscopy studies show enhanced grain growth in the presence of CdCl 2. Glancing angle incidence X-ray diffraction is used for the micro structural study of polycrystalline CdS/CdTe heterostructure at different depths by changing the incident angle. Spraying of CdCl 2 on CdS prior to CdTe deposition promotes S diffusion throughout CdTe film and also Te diffusion into CdS. Whereas spraying of CdCl 2 in between CdTe deposition prevents S diffusion partially and Te diffusion completely. There is an associated change in the microstress of the CdTe film at different layers. The films without CdCl 2 treatment show compressive microstress varying from −98 to −158 MPa with increasing incident angle. CdCl 2 spray during CdTe deposition shows compressive microstress, which varies from −98 MPa at the interface to −19 MPa near the surface and CdCl 2 spray prior to CdTe deposition leads to a mildly tensile stress, from +40 to +20 MPa, which is very close to the standard shear stress of ∼10 MPa for CdTe.

微小部Ｘ線応力測定における最小照射面積と微構造の関係に関する一考察

In order to establish an optimum local stress measurement by the sin2ψ method using micro X-ray beam, Debye-Scherrer rings of three kinds of polycrystalline Al2O3, and Al2O3-10vol%ZrO2 were measured as a function of X-ray irradiation area. Each Debye-Scherrer ring image was obtained from image plate by Cu-Kα or Fe-Kα radiations. X-ray diffraction pattern was also detected from the measured Debye-Scherrer ring image. And then, a correlation between X-ray irradiation volume and X-ray diffraction pattern was examined for each material. The minimum X-ray irradiation volume, where X-ray diffraction pattern and local stress field were approximately equivalent to that from a myriad of grains existed in model materials, was determined. As a result, the minimum irradiation volume was found to correspond to the microstructural volume in which about 104 grains existed randomly. Furthermore, by oscillating the X-ray incident angle, the minimum irradiation volume lowered at the volume in which about 2.8×103 grains existed. Finally, it was confirmed that local stress of polycrystalline Al2O3 could be successfully measured by Synchrotron micro X-ray beam.

Tailored Si3N4 Ceramic Substrates for CVD Diamond Coating

A review is presented of chemical vapour deposition (CVD) diamond coating of silicon nitride (Si3N4) materials. Microcrystalline and nanocrystalline diamond films were grown using microwave plasma (MPCVD) and hot filament (HFCVD) reactors, respectively. Scanning electron and atomic force microscopy, μ-Raman spectroscopy, low incident angle and classical X-ray diffraction, acoustic emission assisted Brale indentation and thermal conductivity measurements were employed for the full characterisation of the diamond/ Si3N4 system. Using these techniques, the nucleation and growth stages as a function of substrate composition and surface pretreatment were characterised, as well as the diamond quality, the existence of residual stresses and the adhesion between the diamond film and the substrate. Based on this study, a tailored material was developed and tested in the machining of hardmetal workpieces with encouraging results.

Low incident angle and classical x-ray diffraction analysis of residual stresses in diamond coated Si3N4

The overall residual stresses and the stress distribution on chemical vapor deposition diamond coated silicon nitride (Si3N4) are investigated by x-ray diffraction using the classical sin2 ψ method and the low incident beam angle diffraction technique, respectively. The deposition time and the substrate surface roughness evidence a clear effect on the film texture and residual stress generation on the diamond coatings. For the roughest substrate, 15 μm polished diamond, as the deposition time increases from 2 to 6 h, a remarkable improvement of the (220) texture and compressive stress relaxation occur from −0.75 to −0.14 GPa. A change to less compressive and even to slight tensile stress takes place for the smoothest substrate, colloidal finished silica, giving stress values of −0.40 and 0.21 GPa for 2 and 6 h of deposition time, respectively. The stress profile along the film thickness for the 6 h grown diamond film on the 15 μm polished substrate exhibits a linear decrease, in absolute values, from a compressive residual stress of −3.7 GPa, in the upper layer of the film, to almost zero stress at the film/substrate interface.

Characterization of heterointerfaces in GaAs/MnAs/MnZn-ferrite structures

We have grown GaAs epitaxial films on MnZn-ferrite substrates using MnAs buffer layers and investigated their heterointerfaces with glazing incidence-angle X-ray reflectivity and X-ray photoelectron spectroscopy. It has been found that the heterointerfaces for this structure are quite abrupt and the roughness at the GaAs/MnAs and MnAs/MnZn-ferrite interfaces are 1.1 and 0.2 nm, respectively. We also found that the diffusion of atoms through the GaAs/MnAs interface into the GaAs film is negligible. These results indicate that the MnAs buffer layer for the GaAs/ferrite structure is chemically stable and promising for the application to the future magnetic electronics.

Deposition of single-phase Cu(In,Ga)Se2 thin films by a novel two-stage growth technique

Homogeneous single-phase quaternary CuInxGa1−xSe thin films were prepared with a reproducible two-step growth technique. The growth process is based on the controlled selenization of sputtered metallic CuIn0.75Ga0.25 alloys in a H2Se reactor at atmospheric pressure. The reaction velocities of the binary selenide phases were carefully controlled to prevent the formation of stable group I–III–VI ternary alloys during a first selenization step. The composite alloys were subsequently annealed in an inert atmosphere, followed by a second selenization step to promote the homogeneous alloying of gallium with CuInSe2. Glancing incident angle x-ray diffraction (GIXRD) at incident angles between 0.5° and 10° revealed virtually no shift in d-spacing with sample depth, which confirmed the monophasic nature of the quaternary alloys. This observation was confirmed by x-ray fluorescence (XRF) studies, revealing a high degree of in-depth compositional uniformity.