Residual Microstrain Research Articles

Characteristics of CuIn1−xGaxS2 thin films synthesized by chemical spray pyrolysis

CuIn1−xGaxS2 multi-component semiconductors thin films were prepared by chemical spray pyrolysis on glass substrates using different concentrations of gallium in the spray solutions (y=([Ga3+]/[In3+]) varying from 0 to 20at% by a step of 5at%). Samples were characterized using X-ray diffraction, Raman spectroscopy, Atomic Force Microscopy, photoluminescence spectroscopy, spectrophotometric and Hall effect measurements. The X-ray spectra reveal that the CuIn1−xGaxS2 thin films are of chalcopyrite crystalline phase with a highly (112) preferential orientation. The best crystallinity is obtained for 10at% Ga incorporation since the maximum (112) peak intensity and grain size are obtained at this Ga incorporation rate. The level of the residual microstrain and dislocation network seems to be reduced respectively to the values 0.09% and 4×108linesmm−2 for an optimum y=10at% for which the crystallinity of CuIn1−xGaxS2 thin layers is the best one. Raman spectra indicate that the sprayed thin films are grown only with CH-ordering. Optical analysis by means of transmission T(λ) and reflection R(λ) measurements allow us to determine the direct band gap energy value which increases by increasing the Ga content and it is in the range 1.39–1.53eV, indicating that CuIn1−xGaxS2 compound has an absorbing property favorable for applications in solar cell devices. Photoluminescence measurements are performed on CuIn1−xGaxS2 crystals and the analysis reveals that the emission is mainly due to donor–acceptor pair transitions. The film resistivity (ρ) and Hall mobility (μ) are strongly affected by Ga incorporation rate. The lowest resistivity (ρ=0.1Ωcm) and maximum value of Hall mobility (μ=0.5cm2V−1s−1) are also obtained for the thin layers prepared with y=10at%. Finally, we reported two new structures for CuInS2/β-In2−xAlxS2/ZnO:Al and CuIn1−xGaxS2 (y=10at%)/β-In2-xAlxS2/ZnO:Al solar cells to investigate the effect of gallium incorporation on the photovoltaic parameters. We found that the Ga-containing cell shows conversion efficiency (η=1.6%) higher than the Ga-free reference cell due to higher open-circuit voltage (Voc=540mV) and short-circuit current density (Jsc=10mAcm−2).

Plastic deformation and sintering of alumina under high pressure

Plastic deformation of alumina (Al2O3) under high pressure was investigated by observing the shape changes of spherical particles, and the near fully dense transparent bulks were prepared at around 5.5 GPa and 900 °C. Through analyzing the deformation features, densities, and residual micro-strain of the Al2O3 compacts prepared under high pressures and temperatures (2.0–5.5 GPa and 600–1200 °C), the effects of plastic deformation on the sintering behavior of alumina have been demonstrated. Under compression, the microscopic deviatoric stress caused by grain-to-grain contact could initiate the plastic deformation of individual particles, eliminate pores of the polycrystalline samples, and enhance the local atomic diffusion at the grain boundaries, thus produced transparent alumina bulks.

Cryomilling effect on the mechanical alloying behaviour of ferritic oxide dispersion strengthened powder with Y2O3

Abstract Cryogenic cooling effect on mechanical alloying of the mixture of Fe–14Cr–3W–0.1Ti and Y 2 O 3 powders was investigated. The powder mixtures were ball milled for 40 h at room-temperature and −150 °C. Cryomilling produced much finer particle/grain size than conventional room-temperature milling. XRD diffraction peak intensity was much lower under cryomilling conditions due to formation of nano-size grains and increased residual microstrain. Absorption amounts of interstitial elements were considerably higher under cryomilling conditions.

X‐ray Diffraction Study of the Effect of High‐Temperature Heat Treatment on the Microstructural Stability of Third‐Generation SiC Fibers

Third‐generation SiC fibers [High Nicalon S (HNS) and Tyranno SA3 (Ty–SA3)] were studied by X‐ray diffraction and transmission electron microscopy (TEM) after heat treatments in neutral atmosphere up to 1900°C. The microstructural changes in both materials were determined using a modified Hall–Williamson method introducing an anisotropy parameter taking into account the high density of planar defects. HNS fibers exhibit significant modifications in the coherent diffraction domains (CDD) size, which drastically increases from 24 to 70 nm in the range 1600°C–1900°C. TEM observations support these results. The residual microstrain values decrease from 0.0015 to 0.0005 between 1750°C and 1850°C. Similarly, the anisotropy parameter significantly decreases in the same temperature range. Concerning the Ty–SA3 fibers, no evolution in terms of CDD size and residual microstrain was observed. However, the anisotropy parameter decreases at 1800°C. TEM observations did not show noticeable grain growth. The grain size was found to be larger than the CDD and the planar defects density to decrease at high temperature. In both types of fibers, the CDD sizes are similar for the highest temperature heat treatments.

Structural disorder of ball-milled, nanosized, Fe-doped SnO2: X-ray diffraction and Mössbauer spectroscopy characterization

Structural characterization of nanosized Fe-doped semiconducting oxide SnO2 is reported. Samples of Sn1−xFexO2−y (with x ranging from 0.11 to 0.33) were processed in a planetary ball mill, subsequently HCl-washed to eliminate metallic iron impurities introduced by the milling tools, and characterized by X-ray diffraction and Mossbauer spectroscopy. Results showed that Fe enters the host matrix randomly replacing Sn in octahedral sites regardless of iron concentration. It has been found the presence of oxygen deficient iron sites attributed to the stoichiometric unbalance of precursor materials used in the milling process. It is known that structural features like particle size and residual microstrain are highly affected by the milling process. Values of average particle sizes as calculated by Scherrer’s method alone decreased with increasing Fe concentration. This result was shown, by means of the Williamson-Hall correction method, to be misleading as a large degree of microstrain is expected for mechanically milled powders. In fact, corrected values of average particle sizes turned out to be reasonably homogeneous regardless of iron content and milling time with no consistent trend. Residual microstrain, on the other hand, was found to increase with iron content giving way to the conclusion that broadening of diffraction peaks are mostly due to increasing microstrain as a function of iron doping and milling time. Williamson-Hall analysis also showed a large degree of particle size inhomogeneity. Milling of undoped SnO2 showed that this inhomogeneity is due mostly to doping as opposed to milling.

Nanoscale planar faulting in nanocrystalline Ni–W thin films: Grain growth, segregation, and residual stress

Abstract

Rietveld structure refinement, cation distribution and magnetic properties of Al3+ substituted NiFe2O4 nanoparticles

Ferrite samples of Al3+ substituted NiFe2O4 nanoparticles were prepared by wet chemical co-precipitation method. The samples were obtained by annealing at relatively low temperature at 600 °C and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and ac susceptibility. On applying the full pattern fitting of Rietveld method using FullProf program, exact coordinates of atoms, unit cell dimensions, atom ion occupancy, degree of inversion as well as crystallite size and residual microstrain have been determined. The lattice parameter, density, particle size, lattice strain, magnetization, magneton number, and Curie temperature are seen to decrease with increasing A13+ content whereas the specific surface area, porosity, coercive force, shows an increasing trend with A13+ content. Cation distribution is obtained from XRD and Rietveld method and the variation of the cation distribution has been discussed on the basis of site preference, size and valence of the substituting cations. The variation of the magneton number with the Al3+ content is satisfactorily explained on the basis of Néel’s collinear spin ordering model. Curie temperature of all the compositions are also obtained theoretically and it agrees with observed Curie temperature.

Synthesis and characterization of nanocrystallized In 2S 3 thin films via CBD technique

Indium sulphide thin films have been successfully synthesized on a glass substrate using a chemical bath deposition method. X-ray diffraction, scanning electron microscopy and atomic force microscopy techniques are used to examine the effect of the experimental conditions on the structure and morphology of the films. The structural analyses suggest the formation of indium sulphide in the early stage, followed in the late stage by the development of β-In 2S 3 nanoparticles with different sizes in the range 16–30 nm and possessing a cubic structure. The surface of the substrate is covered by sphere-like grains in a tightly-adherent state with a relatively uniform thickness of about 100 nm and an average surface roughness of about 35 nm. The mechanism of the film formation apparently involves the Volmer–Weber growth mode. The level of the residual microstrain and dislocation network seems to be reduced respectively to the values 5.3 × 10 −3 and 1.1 × 10 11 lines mm −2 for an optimum deposition time ( t D ) of about 45 min for which the crystallinity of the β-In 2S 3 thin films is the best one.

Thermally activated relaxation behaviour of shot-peened tool steels for cutting tool body applications

Surface residual stress, microstrain and domain size were determined using X-ray diffraction in shot-peened low-alloyed and hot-work tool steels subjected to varying temperatures (200–600°C) and times (0.5–50h). The stress relaxation was directly related to microstrain decrease and domain size increase.The Zener–Wert–Avrami function was used to model the relaxation behaviour. The mechanism responsible for the relaxation behaviour is proposed to be diffusion-controlled as the activation energies for stress and microstrain relaxation were close to the activation enthalpy for lattice self-diffusion of alpha-iron.The relaxation rate varied over time and temperature. At temperatures up to 300°C, the relaxation rate was insignificant in all the steels. In the temperature range of 300–400°C and 400–550°C for low-alloyed and hot-work tool steels, respectively, the stresses decreased at a similar rate with increasing time and temperature. At the tempering temperatures of the steels, the stress relaxation was controlled by microstructure transformations. A stress relaxation stabilization was found in one of hot-work steels between 450 and 500°C at annealing times longer than 3h.

Caracterización microestructural de aleaciones base cobre obtenidas mediante molienda reactiva

The micro and nanostructure of Cu-Al, Cu-V and Cu-Ti alloys produced by reactive milling were analyzed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Samples with different milling times (t= 0, 10, 20 and 30 h) were considered. The grain size, dislocation density and residual microstrain were evaluated form the XRD data using the Williamson-Hall and Klug-Alexander methods. The evolution of texture as a function of milling time was also studied using XRD. It was found, using TEM, that the grain size and dispersoid size were nanometric in all three alloys considered.

The Robot Concept at STRESS-SPEC for the Characterisation or Semi-Finished Products

The materials science diffractometer STRESS-SPEC located at Forschungsneutronen¬quelle Heinz Maier-Leibnitz (FRM-II) in Garching/Germany is a dedicated instrument for residual strain, texture and microstrain analysis. Comparably low gauge volumes of 1x1x1mm³ for gradient investigations in many types of materials can be investigated. A robot system consisting of a robot type Stäubli RX160, a laser tracker and a heavy vibration free basement was installed to overcome limitations in gradient investigations of residual stresses and crystallographic textures in semi-finished and finished products. The robot can carry up to 30kg with precise positioning. Al7020, an Al-alloy for airspace application, was used to perform a first global texture measurement using the robot.

Measurement of the residual macro and microstrain in strained Si/SiGe using Raman spectroscopy

ABSTRACTThe use of laser Raman spectroscopy to assess the residual strain in strained silicon/silicon germanium devices is well established. The peak shift associated with the 520cm−1 silicon peak can be used to directly measure the strain in the cap layer provided that the strained silicon peak can be deconvoluted from the more intense Si in SiGe peak which occurs at slightly lower wavenumbers. However, though peak position gives a measure of the macrostrains in the layer it is not useful for the assessment of microstrains associated with point defects which may also influence device performance; such microstrains influence the intensity of the Raman peaks and can, in principle, be monitored by this method. In this study we have undertaken a study of peak shape as a function of processing conditions for strained silicon on SiGe. Changes in peak position may be correlated with macrostrains and macrostrain relaxation around extended defects such as dislocations. Changes in peak width can be correlated with processes which lead to changes in composition (e.g. germanium build-up in the surface after etching) and microstrain. Such changes are not necessarily correlated with changes in macrostrain but indicate that microstrain could also be an important factor influencing device performance.

The Microstrain Generation in Cryomilled Nickel by Impurity Nitrogen Atoms

ABSTRACTThe residual microstrains in cryomilled Ni powders, processed under various cryomilling conditions, are measured by XRD and analyzed using a single line approximation (SLA) method. The results show that the average residual microstrains are in the range of 2×10-3 ∼ 6×10-3, and the residual microstrain on the (200) plane is higher than those on the other planes by 33 %. The measured microstrain is proposed to evolve from the introduction of N as impurity atoms in Ni lattice may be attributed to the evolution of the residual microstrain. The N atoms tend to stay in the octahedral sites of Ni, and the diameter of N atom is larger than that of the octahedral site of Ni by 48 %. Accordingly, a lattice strain field is expected around interstitial N atoms that are located at octahedral sites. By comparing the crystal structure around the octahedral site of Ni with that of Ni3N structure, the lattice strains are estimated to be in the range of 5 ∼ 15 %. The results show that the (200) plane has the lattice strains that are two times higher than those in other planes, and this is argued to be the reason for the measured anisotropy of residual microstrain in Ni after cryomilling.

パルス電解により形成したクラックフリークロム層の残留応力と微視的ひずみに及ぼす電解条件の影響

The residual stress and microstrain of crack-free Cr layers deposited by pulse current electrolysis was evaluated by X-Ray diffraction methods. Changing the on-time and off-time periods, various residual stresses were measured. The residual stress was influenced by the off-time period in the same on-time period. In order to obtain Cr layers that have compressive residual stress, a suitable off-time period corresponding to the on-time period should exist. When the off-time period was too short or too long compared to the suitable off-time period, tensile residual stress was generated in the Cr layer. With increasing bath temperature and current density, the residual stress became more compressive. Microstrain decreased at high bath temperatures and low current densities. The amount of change in the residual stress due to heat treatment correlated with the microstrain, and became smaller and more stable with heat treatment as the microstrain decreased. The Vickers hardness of the Cr layer was governed by microstrain; the hardness increases with increasing microstrain.

Effects of energetic particle bombardment on residual stress, microstrain and grain size of plasma-assisted PVD Cr thin films

Residual stress, microstrain and grain size of ion plated Cr films deposited on molybdenum substrates were analyzed and studied. A model based on the effects of incident particle energy and/or momentum on the properties of these films is proposed and discussed. It was concluded that the film properties may be affected by both the momentum and energy transfer of the incident particles, or by either one.

On the influence of N on residual microstrain in cryomilled Ni

The factors that influence the development of residual microstrain during milling in a liquid nitrogen atmosphere, defined hereafter as cryomilling, are investigated. The residual microstrains in cryomilled Ni, processed under various cryomilling conditions, were examined by X-ray diffraction (XRD) and analyzed through the single line approximation (SLA) method. The average residual microstrains are determined to be in the range of 2×10−3 to 6×10−3. The residual microstrain on the (200) plane is higher than those on the other planes by 33 pct. The residual microstrain and its anisotropy in Ni are reduced after heat treatment at 800 °C for 1 hour. The measured microstrain is proposed to evolve from the presence of N and O as impurity atoms in the Ni lattice. Both N and O are introduced from the environment and then their solubility in Ni is enriched via the generation of defects that occurs during cryomilling. The stable site for N and O atoms in Ni is the octahedral site, and the sizes of N and O atoms exceed those of the octahedral site of Ni by 48 and 16 pct respectively. Accordingly, a lattice strain field is expected around interstitial N atoms that are located at octahedral sites. By comparing the crystal structure around the octahedral site, the stable site for impurity N atoms, in the Ni lattice with that of Ni3N structure, the lattice strains are estimated to be in the range of 5 to 15 pct. The result shows that the (200) plane has strains that are 2 times higher than those in other planes, and this is argued to be the reason for the measured anisotropy of residual strain in Ni after cryomilling.

X-Ray Diffraction Line Broadening from Gold and Platinum Thin Films

X-ray diffraction line profile analysis has been used to study the microstructure of (Ill) oriented gold and platinum thin films deposited by thermal evaporation and DC magnetron sputtering. In addition to crystallite size broadening, the profiles from these films displayed broadening arising from dislocations. A parallel investigation, using transmission electron microscopy (TEM) was undertaken to study the nature of dislocations formed, and to provide information on the dimensions of the crystallite columns in the films. X-ray data were collected at room temperature to determine the anisotropy of the broadening with (hkl), using a Siemens D5000 powder diffractometer (CuKa radiation) and two high-resolution synchrotron instruments (BM 16 at the ESRF [A=0.35A] and station 2.3 at the Daresbury laboratory. Two approaches to instrument deconvolution were investigated; Fourier deconvolution and fundamental parameters profile fitting, using Lab6 as a reference material to determine the instrument profile function. After removal of the crystallite size broadening contribution from the measured integral breadths, the residual microstrain broadening was modelled assuming dislocations based on a FCC a/2 { Ill} slip system. The results of the X-ray analysis agreed with dark field TEM micrographs, which showed that many of the crystallites contained dislocations of mixed character (screw- edge).

Tin Oxide Thin‐Film Sensors for Aromatic Hydrocarbons Detection: Effect of Aging Time on Film Microstructure

SnO2 thin films for gas‐sensor devices were deposited by pulsed laser ablation on <h00> silicon wafers and on substrate heater elements with 200 nm thick Si3N4 membranes as physical supports of the sensor stack. Microscopic analysis showed that the thin films were polycrystalline, with ∼40‐60 nm equiaxial grains, high porosity, and high specific surface area. The sensors were exposed to gas mixtures containing benzene, wet synthetic air, and CO, with 0.5 ppm of benzene added to 30% relative humidity synthetic air and 20 ppm CO. A 100% relative conductance variation, DeltaI/I0, of the sensing layer was observed. However, this DeltaI/I0 value consistently decreased after prolonged testing (up to 2 weeks) in a gas‐sensor chamber. The sensing layer was studied using several analytical techniques to understand the aging time effects on sensor performance under working conditions. X‐ray diffractometry showed a marked decrease of the residual microstrain after prolonged heat treatments, suggesting a substantial reduction of lattice (point and line) defects. Furthermore, photothermal deflection spectroscopy highlighted a consistent decrease of the sensing layer absorption coefficient near 1 eV that could be related to a reduction of carrier concentration. Because structural defects in SnO2, such as oxygen vacancies or dislocations, are electrically active and variations in the carrier concentration are, at least in part, related with changes in the defect density, the annealing of these defects might have accounted for the observed worsening of sensor performance with the aging time.

Crystallographic preferred orientation induced by cyclic rolling contact loading

Fine focus X-ray diffraction methods have been applied to analyze the texture development of the ferrite phase during rolling contact fatigue of 6309 type deep groove ball bearing inner rings prepared from hardened and tempered SAE 52100 steel. Textures of the ferrite matrix as {100}〈110〉 and {111}〈211〉 (where {hkl} denotes the crystallographic plane that is preferably parallel with the contact surface and 〈uvw〉 denotes the crystallographic direction that is preferably parallel with and in the direction of over-rolling) have been identified in a small region below the rolling contact surface. These textures develop gradually with an increasing number of stress cycles and become noticeable in conjunction with changes in residual stress, microstrain, and volume fraction of retained austenite in the same region. Upon rolling contact loading, both textures can become very pronounced, while the shape of the subsurface volume, where plastic deformation takes place in particular, remains unchanged: material displacement in the subsurface volume is less than 5 µm in the three principal directions. Crack propagation in association with spalling fatigue failure has been shown to be related to the type of texture developed.

Thermal effects of residual macrostress and microstrain in plasma-assisted CVD TiN films

The effects of both the deposition and tempering temperatures on the residual macrostress and microstrain are investigated in plasma-assisted chemical vapour deposition (PACVD) TiN films. Unlike the case of thermal CVD processes, the residual macrostress in PACVD TiN films decreases with the increase of the deposition temperature and shows a dramatic drop once the temperature is above 700 °C. The residual microstrain, indicated by peak broadening and a stress-free lattice constant, exhibits the same variation with the deposition temperature. This implies that the competition for the formation of stress and strain is related to the coating process and that the macrostress in PACVD TiN film is usually of an intrinsic nature. Nevertheless, the thermal stability of macrostress behaves differently from that of microstrain. The tempering treatment tends to release residual macrostress but shows little effect on the microstrain detected by the X-ray method. Different origins may exist for the macrostress and microstrain in the film, although only those films deposited at relatively low temperatures and, hence, involved mainly with intrinsic macrostresses display a significant relaxation rate.