Grazing Incidence X-ray Diffraction Techniques Research Articles

Effect of titanium interlayer configurations on residual stresses and performance of titanium/titanium nitride multilayer coatings

Multilayer coatings provide an effective measure to control and optimise of residual stresses, enhance coating adhesion, fracture toughness, wear and corrosion resistance of coating system. In this study, we designed and produced bi-layer and four-layer titanium/titanium nitride magnetron sputtered coating configurations by altering the position of the interlayer. The in-plane residual stresses in different coating configurations are measured by multiple peak grazing incidence X-ray diffraction techniques. Subsequently, the effect of different compressive residual stresses on adhesion, mechanical properties, wear and corrosion resistance of coatings are investigated. Results show that the position of interlayer in multilayer coating configuration has a great impact on relaxation of residual stresses. The residual stresses are relieved by 26% and 46% by lowering the position of titanium interlayer from 800 nm at the top to 1000 nm and 1200 nm, respectively. The nanoindentation hardness is decreased by 11% and 13%, respectively. The wear rate of multilayer coating having interlayer position at 800 and 1000 nm from the top is ≈ 23% lower compared to bilayer however it is increased by ≈ 50% when interlayer coatings position changed to 1200 nm from the top. The interposition of interlayer in multilayer coating configurations decreased the corrosion current density by ≈ 50%. All multilayer coatings including higher residual stresses show better adhesion to the substrate compared to bilayer coatings which shows severe delamination.

Compact sample environment for in situ X-ray scattering during spin-coating.

We demonstrate a compact sample environment for the in situ study of crystallization kinetics of thin films on synchrotron beamlines, featuring atmospheric control, automated deposition, spin-coating, and annealing stages. The setup is suitable for studying thin film growth in real time using grazing-incidence X-ray diffraction techniques. Humidity and oxygen levels are being detected by sensors. The spinning stage exhibits low vertical oscillation amplitude (∼3μm at speeds up to 10 000 rpm) and can optionally be employed for antisolvent application or gas quenching to investigate the impact of these techniques, which are often used to assist thin film growth. Differential reflectance spectroscopy is implemented in the spin-coater environment for inspecting thin film thickness and optical properties. The infrared radiation-based annealing system consists of a halogen lamp and a holder with an adjustable lamp-to-sample distance, while the sample surface temperature is monitored by a pyrometer. All features of the sample environment can be controlled remotely by the control software at synchrotron beamlines. In order to test and demonstrate the performance, the crystallization pathway of the antisolvent-assisted MAPbI3 (MA = methylammonium) perovskite thin film during the spinning and annealing stages is monitored and discussed.

Change in the gas sensing mechanism and improved sensing response on ion-irradiated palladium-graphene oxide nanocomposite

In this study, we synthesized Pd-graphene oxide (Pd-GO) nanocomposite layers on SiO2/Si substrates using chemical method. Pd-GO layers were treated with swift heavy ion irradiation (100 MeV Ag ions, 1013 ions/cm2). The structural properties of the pristine as well as the ion irradiated samples were investigated using synchrotron grazing incidence x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. XRD shows peaks corresponding to Pd (FCC, space group-Fd-3m), GO and synthetic graphite. The relative graphite peak intensities increased after ion irradiation, indicating reduction of GO. The sensor responses of nanocomposite layers towards exposure of 35 ppm H2 at 100 °C, were measured for several cycles. Ion-irradiated Pd-GO samples show enhancement in the sensing response of H2 gas by about 24% and with lower recovery times (25%), as compared to pristine Pd-GO nanocomposite samples. The change in type of conductivity from p-type gas sensing layer in pristine nanocomposite to n-type conductivity, along with an increase in conductivity (about 500 times) in ion irradiated samples were observed. The change in type of conductivity on ion-irradiation is attributed to the reduction of GO layer and the changes in conductivity on hydrogen exposure is explained due to hydrogen spill-over effect in the two-component system. The improvement in sensitivity upon ion-irradiation was due to the increase in concentration of structural defects due to electronic energy loss, as studied by SRIM simulation. This study points towards using ion induced electronic energy loss as a new tool for varying the gas sensing properties of GO based sensors.

Humidity-Insensitive, Large-Area-Applicable, Hot-Air-Assisted Ambient Fabrication of 2D Perovskite Solar Cells.

2D layered perovskites (LPs) have shown great potential to deliver high-performance photovoltaic devices with long-term stability. Despite many signs of progress being made in film quality and device performance, LP films are mainly processed in strict conditions and through non-scalable techniques. Here, the hot-air-assisted ambient fabrication technique is introduced to prepare LP films for efficient and stable solar cells. The high-quality LP films with good crystallinity, preferable orientation and desirable morphology are obtained by balancing the crystal nucleation and growth processes. Employing the synchrotron-based in situ grazing-incidence X-ray diffraction technique, hot air induces the solidification of solutes and forms an intermediate at the air-liquid interface, which transforms into 3D-like perovskite, followed by the growth of the 2D species toward the substrate. The optimal LP film delivers a device power conversion efficiency of 16.36%, the best value for the LP-based solar cells prepared by the non-spin-coating techniques. The solar cell performance is insensitive to the film processing humidity and the device size is upscalable, which promises real-world deployment of LP-based optoelectronic devices.

Study of oxidation behaviour of Ruthenium thin film after thermal annealing in oxygen environment

In the present study, 20 nm thick Ru film ion beam sputtered on Si substrate is annealed at different temperatures ranging from 100 °C to 600 °C for 2 hours in an oxygen environment. The sample was characterized by grazing incidence x-ray reflectivity and grazing incidence x-ray diffraction techniques that revealed that there is no oxidation of Ru below 400 °C in 150 standard cubic centimetre O2 flow environment. At 400 °C, the oxidation of the Ru thin film starts and at 500 °C both Ru and RuO2 phases co-exists. At higher temperature (600 °C), the Ru thin film oxidized into RuO2 phase and an intermixed layer of Ru and Si at the film substrate interface is revealed.

Langmuir monolayers as models of the lipid matrix of cyanobacterial thylakoid membranes

Cyanobacteria are omnipresent photosynthetic microorganisms that are crucial for the proper functioning of multiple environmental niches. Recently, these organisms have found various applications in soil remediation, waste utilization, and the production of biodegradable polymers. A significant volume of the cyanobacterial cell is occupied by thylakoid membranes, where the photosynthesis process is localized. These membranes are inhomogeneous and highly compartmentalized; however, the stimuli and forces leading to such a high degree of self-organization are not entirely understood. In our study, we apply Langmuir monolayers formed by the main lipids of cyanobacterial membranes: monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG), and phosphatidylglycerol (PG), as versatile models of thylakoid membranes. Special attention was paid to the binary system formed by the two neutral glycolipids MGDG and DGDG, as these two substances are most abundant in the membrane. Then the effects implied by the incorporation of anionic lipids were investigated. The morphology of the monolayers was studied by Brewster angle microscopy, while the ordering of the monolayer-forming molecules on the molecular scale was investigated with the Grazing incidence X-ray diffraction technique. It was proved that the inhomogeneous structure of cyanobacterial membrane is an intrinsic property of the applied structural lipids. It was also proved that the increase in anionic lipid content, frequently applied by cyanobacteria as a response to unfavorable environmental conditions, leads to significant changes in the morphology of the model membranes.

In Situ Observing and Tuning the Crystal Orientation of Two-Dimensional Layered Perovskite via the Chlorine Additive.

Precise control of crystal orientation in two-dimensional (2D) layered perovskites (LPs) is vital for their optoelectronic applications due to the structure-induced anisotropy in optical and electrical properties. Herein, we directly observe and control the crystal orientation of the butylammonium-based 2D LP films. Employing the synchrotron-based in situ grazing-incidence X-ray diffraction technique, we reveal the orientation modulation mechanism of the Cl additive by following the crystallization dynamics and chemical conversion pathways during film formation. Two new Cl-related intermediates are identified which serve as templates directing the orientational growth of the 2D LP films. We fine-tune the crystal orientation of 2D LP films through the Cl additive and incorporate the films with the requisite crystal orientations in solar cells and photodetectors. The optoelectronic performances of the devices show a strong correlation with the crystal orientation of the 2D LP films.

Subsurface damage layer of bulk single-crystal potassium dihydrogen phosphate (KDP) after SPDT: studied by the grazing incidence X-ray diffraction technique

This work proposes a novel way of the subsurface damage layer characterization for bulk single-crystal optical material, based on the X-ray grazing incidence technique (GIXRD). The result shows that the subsurface damage layer of bulk single-crystal potassium dihydrogen phosphate (KDP) mainly consists of polycrystalline KDP and bulk single-crystal matrix after single-point diamond turning (SPDT). Meanwhile, it is found that the polycrystalline KDP presents some kinds of preferred orientations, which depend on the SPDT surfaces and SPDT track u . For example, the polycrystalline texture of (010) SPDT surface is p (103)// u and p (204)// u , while the polycrystalline texture of (111), I-type and II-type SPDT surfaces are p (312)// u , p (332)// u and p (202)// u , respectively. These findings allow us to further understand the subsurface damage layer of bulk single-crystal KDP after SPDT.

Non-destructive measurement of grinding-induced deformation-depth using grazing incidence X-ray diffraction technique

The present research work proposes a non-destructive methodology to detect and measure subsurface deformation using Grazing incidence X-ray diffraction (Gi-XRD). The FWHM of the XRD peak that indicates the degree of plastic deformation was measured at different X-ray penetration depths by changing the angle of incidence during Gi-XRD. However, these FWHM values do not represent the actual FWHM at a particular depth because it also captures the effect of the top layers. Therefore, the FWHM values were further analysed to get the actual FWHM for a particular penetration depth and correlated with the deformation depth. The non-destructively measured deformed layer thickness was verified against the results of the metallographic study and a deviation of around 1.2 μm was recorded.

Quasi-Homoepitaxial Junction of Organic Semiconductors: A Structurally Seamless but Electronically Abrupt Interface between Rubrene and Bis(trifluoromethyl)dimethylrubrene

Single-crystalline organic semiconductors exhibiting band transport have opened new possibilities for the utilization of efficient charge carrier conduction in organic electronic devices. The epitaxial growth of molecular materials is a promising route for the realization of well-crystallized organic semiconductor p–n junctions for optoelectronic applications enhanced by the improved charge carrier mobility. In this study, the formation of a high-quality crystalline interface upon “quasi-homoepitaxial” growth of bis(trifluoromethyl)dimethylrubrene (fmRub) on the single-crystal surface of rubrene was revealed by using out-of-plane and grazing-incidence X-ray diffraction techniques. Ultraviolet photoelectron spectroscopy results indicated abrupt electronic energy levels and the occurrence of band bending across this quasi-homoepitaxial interface. This study verifies that the minimization of the lattice mismatch enhances the crystalline qualities at the heterojunctions even for van der Waals molecular condensates, potentially opening an untested route for the realization of high-mobility organic semiconductor optoelectronics.

Stachys byzantina extract: A green biocompatible molecules source for graphene skeletons generation on the carbon steel for superior corrosion mitigation

The presence of bio-active compounds in Stachys byzantina (SB) extract has made it a powerful source of green inhibitors in controlling steel corrosion. In this study, it has been attempted to create a highly durable corrosion protective film on the surface of the metal with SB and divalent zinc (II) cations and investigated them by Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic polarization (PP) tests, and surface analysis methods. EIS results show that after 24 h of placing the steel samples in 3.5% NaCl solution containing 700 SB − 300 ZN, the synergistic corrosion inhibition behavior was about 92%. Besides, the results of the PP demonstrated a significant reduction of the icorr. Furthermore, surface analyses such as Field Emission Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (FE-SEM/EDS) and Atomic Force Microscopy (AFM) images illustrated the low metal surface degradation, which indicates that the mix of SB and Zn caused a protective layer creation on the surface, especially for SB 700 - Zn 300. Also, new compounds of graphitic materials’ structure were made using SB extract which is a natural-based chemical, and investigated by Fourier-Transform Infrared Spectroscopy (FTIR) test, Grazing Incidence X-ray Diffraction (GIXRD) technique, Ultraviolet–visible spectroscopy (UV–Vis) analysis, and Raman spectroscopy.

Ellipsometric investigation of AlN thin films - Effect of temperature and doping with Ti,Cr

Spectroscopic Ellipsometer is employed to study the optical properties (including complex refractive index and bandgap) of pristine and doped AlN (Ti and Cr) films as a function of doping concentration and temperature (273 K–573 K). Pristine AlN, Al1−xTixN (x = 1.5, 3 and 4 at%) and Al1−xCrxN (x = 2, 4 and 6 at%) films are grown on Si(100) substrates using magnetron sputtering technique. The crystal structure and chemical composition of the as grown films are analyzed using Grazing Incidence X-ray Diffraction (GIXRD) and X-ray Photoelectron Spectroscopy (XPS) techniques, respectively. The optical properties of Ti, Cr doped AlN films at a wider range of energies as well as different ambient temperatures are reported. To determine the complex refractive indices, the measured ellipsometric parameters Is and Ic are fitted using a five layer model with Lorentz oscillator dispersion relation. As far as the bandgap region is concerned, both the real and imaginary parts of the refractive index show significant changes near the bandgap. It is observed that, the real part of refractive index of AlN increases monotonically with the increase in Ti doping and opposite in Cr doping. The extinction coefficient is relatively larger for Cr-doped AlN compared to Ti-doped AlN films. With the increase in doping concentration, the bandgap is found to decrease rapidly for Cr-doped AlN in comparison to Ti-doped AlN films. Additionally, a significant change in the complex refractive index of doped AlN films is observed with temperature.

X-ray scattering profiles: revealing the porosity gradient in porous silicon

Porous silicon layers with different porosities were prepared by adjusting the anodization current density of the electrochemical etching process, starting from highly doped p-type crystalline silicon wafers. The microstructural parameters of the porous layers were assessed by high-resolution X-ray diffraction, total external reflection, scanning electron microscopy and nitrogen adsorption–desorption analysis. Furthermore, both the surface porosity and the mean porosity for the entire volume of the samples were estimated by employing total external reflection measurements and X-ray reciprocal-space mapping, respectively. The results clearly indicate that the surface porosity is different from the mean porosity, and the presence of a depth porosity gradient is suggested. To evaluate the porosity gradient in a nondestructive way, a new laboratory method using the grazing-incidence X-ray diffraction technique is reported. It is based on the analysis of the X-ray scattering profiles of the porous layers to obtain the static Debye–Waller factors. In this way, a description of the porosity gradient in a quantitative framework becomes possible, and, as a result, it was shown that the porosity increases exponentially with the X-ray penetration depth. Moreover, a strong dependence between the porosity gradient and the anodization current was demonstrated. Thus, in the case of the lowest anodization current (e.g.50 mA cm−2) a variation of only 15% of the porosity from the surface to the interface is found, but when applying a high anodization current of 110 mA cm−2the porosity close to the bulk interface is almost three times higher than at the surface.

High-Temperature Air and Steam Oxidation and Oxide Layer Characteristics of Alloy 617

Nickel-based superalloys are the candidate materials for many high-temperature applications, especially in advanced ultra-supercritical coal-fired power plants and in the next-generation nuclear power plants. This paper reports the results of a comprehensive study on chemical composition, structure and kinetics of oxide film formation of a nickel-based superalloy, alloy 617, in ambient air and steam at 750 °C for a duration of 500 h. The morphology and nature of oxide scales have been characterized by scanning electron microscope with energy-dispersive x-ray attachment, grazing incidence x-ray diffraction technique and glow discharge optical emission spectrometry (GDOES). The mass gain of alloy 617 in steam was higher than that in air, and followed a parabolic rate law for both atmospheres. The depth profiles of the oxide films obtained by GDOES showed the presence of an outer chromium oxide scale with mixed oxides of nickel and aluminum at the interface. The oxidation kinetics of alloy 617 and the nature of oxide scales formed during the steam and air oxidation are discussed.

Modulation of perovskite crystallization processes towards highly efficient and stable perovskite solar cells with MXene quantum dot-modified SnO2

MQDs-SnO2-modulated perovskite crystallization processes visualized by in situ 2D GIXRD technique.

Synthesis of Hydrogen Getter Zr1-xCox (x=0-1) Alloy Films by Magnetron Co-Sputtering

The Zr1-xCox(x=0, 0.25, 0.53, 0.63, 1) thin films were deposited on quartz substrate using magnetron co-sputtering of Zirconium and Cobalt targets in confocal geometry. A constant pulsed direct current (PDC) on Zirconium and radio frequency (RF) of various powers on Cobalt target were applied to vary the concentration of Co in the Zr1-xCox film. The film composition was quantified using EDX measurements. The hydrogen storage capacity of these films was studied using an in-house developed hydrogen adsorption setup, in which the electrical resistivity of the film was monitored as a function of hydrogen partial pressure and temperature. The films' surface morphology and crystal structure before and after hydrogenation were characterized using atomic force microscopy and grazing incidence X-ray diffraction techniques using synchrotron radiation, respectively. An increase in the particle size after hydrogenation was observed for all the films. An increase in resistivity was also observed due to the absorption of hydrogen in all the compositions. The near stoichiometric film Zr0.47Co0.53 showed the highest hydrogen absorption level at 200 oC at all partial pressures. However, a decrease in the response at temperatures higher than 200 oC was observed in the film containing a Co concentration. The mechanism for the increase in resistivity of the film on hydrogenation is explained

Highly Thermostable and Efficient Formamidinium-Based Low-Dimensional Perovskite Solar Cells.

Currently, most two-dimensional (2D) metal halide perovskites are of the Ruddlesden-Popper type and contain the thermally unstable methylammonium (MA) molecules, which leads to inferior photovoltaic performance and mild stability. Here we report a new type of MA-free formamidinium (FA) based low-dimensional perovskites, featuring a general formula of (PDA)(FA)n-1 Pbn I3n+1 with propane-1,3-diammonium (PDA) as the organic spacer cation. The perovskite films with well-oriented crystal grains are attained under the assistance of the FACl additive, where the role of Cl is investigated through the grazing-incidence X-ray diffraction technique. The photovoltaic device based on the optimized (PDA)(FA)3 Pb4 I13 film demonstrates a remarkable power conversion efficiency of 13.8 %, the highest record for the FA-based 2D perovskite solar cells. In addition, compared to (PDA)(MA)3 Pb4 I13 , the MA-containing analogue and a renowned stable 2D perovskite, both the (PDA)(FA)3 Pb4 I13 films and their derived devices exhibit exceedingly higher thermal stability.

Unravelling the structural changes of phospholipid membranes in presence of graphene oxide

Graphene-based nano-technology is the future of biomedical devices including biosensors and, hence, it is essential to unravel the interaction of graphene oxide (GO) with cellular membrane. Here, the structural reorganization of lipid molecules, which are the building blocks of a cellular membrane, has been demonstrated in presence of GO flakes. The membrane is mimicked by forming a stack of lipid bilayers of zwitterionic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and its structures have been probed by X-ray reflectivity and grazing incidence X-ray diffraction techniques. Lipid-GO composites have exhibited two sets of lamellar diffraction peaks illustrating GO-rich micro-domains in the matrix of phospholipid bilayers (GO-poor phase). In these domains, the GO flakes are observed to penetrate into hydrophobic core of the bilayer altering the thickness along with the overall electron density profile of the lipid layer. The GO-poor bilayer is closely related to the phase formed by pristine lipid molecules. The lattice parameters of a body-centred rectangular unit cell formed by chains of saturated phospholipids are found to be modified in presence of GO with a significant effect on molecular tilt. The structural description of GO-membrane interaction may pave the way of discerning the physical behaviour of the composites.

Electric-field-manipulated crystal stacking for high-quality organic–inorganic halide perovskites

An external electric field (EEF) was applied to regulate perovskite crystal growth in order to achieve the preferred crystallization. The out-of-plane and in-plane crystallization of MAPbI3-xClx, MAPbI3 and Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 perovskites was compared based on the grazing incidence X-ray diffraction technique. The results showed that vertical EEF stretches the perovskite crystals, making them exhibit vertical preferential growth on the substrate while shortening the lateral stacking spacing. Although the upward and downward EEF directions showed a similar regulatory effect on crystallization, they exhibited opposing effects on the built-in field in a photovoltaic device. This work reveals the mechanism of perovskite crystal stacking under an external field.

Impeded Molecular Reorganization by Polyethylene Glycol Conjugation Revealed by X-ray Reflectivity and Diffraction Measurements.

Polyethylene glycol (PEG) coatings have been widely applied in pharmaceutical and biomedical systems to prevent nonspecific protein absorption, increase vesicle blood circulation time, and sustain drug release. This study systematically investigated the planar interfacial organization of phospholipid monolayers containing various amounts of PEG conjugations before and after enzyme-catalyzed degradation of the lipids using X-ray reflectivity and grazing incidence X-ray diffraction techniques. Results showed that attaching PEG to the headgroup of the lipids up to 15 mol % had limited effects on molecular packing of the lipid monolayers in the condensed phase at the gas-liquid interface and negligible effects on the enzyme adsorption to the interface. After enzyme-catalyzed degradation, equimolar fatty acids and lyso PC were generated. The fatty acids together with the subphase Ca2+ self-assembled into highly organized multilayer domains at the interface. The X-ray measurements unambiguously revealed that the densely packed PEG markedly hindered microphase separation and formation of the palmitic acid-Ca2+ complexes.