Grazing Incidence X-ray Diffraction Research Articles

Double-pentagon silicon chains in a quasi-1D Si/Ag(001) surface alloy

Silicon surface alloys and silicide nanolayers are highly important as contact materials in integrated circuit devices. Here we demonstrate that the submonolayer Si/Ag(001) surface reconstruction, reported to exhibit interesting topological properties, comprises a quasi-one-dimensional Si-Ag surface alloy based on chains of planar double-pentagon Si moieties. This geometry is determined using a combination of density functional theory calculations, scanning tunnelling microscopy, and grazing incidence x-ray diffraction simulations, and yields an electronic structure in excellent agreement with photoemission measurements. This work provides further evidence of pentagonal geometries in 2D materials and heterostructures and elucidates the importance of surface alloying in stabilizing their formation.

Tuning Electrostatics to Promote Ordered Monolayers of Phosphole-Lipids.

Heteroatom-doped π-conjugated systems have been exploited for electronic device applications. Phosphole-containing backbones are particularly intriguing with regard to electron delocalization and ultimately control over the photophysical, redox, and charge transfer characteristics. However, practical application of these materials commonly relies on well-structured, thin film architectures. Self-assembly offers a route to generate ordered 2D structures deposited on solid substrates. The orientation of these deposited films can be manipulated by the introduction of alkyl chains of varying length (to form phosphole-based lipids) and chemical modification of the phosphole-derived headgroup. External controls can also be considered to tune these films' properties, e.g., the electrostatic interactions within the film can be controlled by varying the environment with the addition of simple salt counterions. A series of lipids with phosphole-based π-conjugated headgroups have been designed and exhibit intramolecular conformational changes in response to external conditions. Herein the 2D film structure in Langmuir and Langmuir-Blodgett films is reported in the presence and absence of halide salts. The film morphology obtained from Brewster angle and atomic force microscopy shows the formation of a condensed phase but also 3D aggregates, and grazing incidence X-ray diffraction confirmed the presence of untilted, hexagonally packed chains. The size of the counterion influences its ability to intercalate between the phosphole headgroups, which ultimately provides a means to induce the formation of a well-ordered, single monolayer film without aggregates that can be transferred to the solid substrate.

Study in the Extreme UV Range of the Spectral Transmission of Nickel Plasma Created under the Effect of an X-Ray Pulse of the Z-Pinch

Spectral properties of the high-temperature plasma obtained by exposing a nickel layer to a source of high-power X-ray radiation (a power of 6–10 TW with a duration of 7–10 ns) based on a Z-pinch, formed during implosion of tungsten multi-wire arrays at the Angara-5-1 facility, are studied. In this case, the Z-pinch radiation heats the target and turns it into the hot plasma, and the same radiation probes the target plasma to determine the spectral dependence of the transmission of this plasma. An original scheme is proposed for measuring the incident, transmitted and self-emission of a target simultaneously in one experiment in the frame mode using a grazing incidence diffraction spectrograph. Using laser shadow imaging, experimental data are obtained on the velocity of the plasma expansion on the irradiated and back sides of the target, which reached 100 km/s. Targets made of thin Ni layers deposited on a mylar film are studied. An irradiationinduced multiple increase in the transmission of the target plasma in the EUV range is observed compared to the transmittance of the target in the cold state. The dependence of the absorption spectrum of the plasma and the accompanying self-radiation of the target on the power and shape of the heating pulse is studied. The measurement results are compared with numerical calculations performed using the RALEF-2D two-dimensional radiation code, which has been repeatedly used previously to simulate similar experiments. The shape of the spectral dependence of the transmission in the experiment and calculation is similar in the range of ∼30–200 Å, but the model plasma transmission (∼0.8–0.9) is higher than that obtained using a spectrograph and X-ray multi-frame photography (∼0.5–0.6).

Improvement in bioactivity, hardness and friction resistance of 3 % manganese-doped hydroxyapatite coated on alumina using radio frequency magnetron sputtering

Hydroxyapatite (HAP) is a common hard tissue implant material known for its superior biocompatibility and osteoconductivity. However, its poor mechanical strength, brittleness and slow degradation limit the applications. This study explores the enhancement of HAP mechanical properties and bioactivity by coating 3 wt% manganese-doped HAP (Mn-HAP) on another inert biomaterial alumina (Mn-HAP/Al2O3) substrates using the RF magnetron sputtering technique. Characterization of these samples was performed using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDS), Grazing Incidence X-ray Diffraction (GIXRD), Fourier Transform Infrared Spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) techniques. Mechanical property was assessed through Vicker's hardness and adhesion of the film was studied by scratch testing. Corrosion resistance was evaluated using Tafel plots in Ringer's solution by Electrochemical analyser (ECA), and dielectric properties were measured using Impedance analyser. Biocompatibility was examined by wettability tests, thrombogenicity, antioxidant test, antimicrobial investigation and MTT [3-(4, 5-dimethythiazol-2-yl)-2, 5-diphenyl tetrazolium bromide] assay. The results show that Mn-HAP/Al2O3 coatings exhibit superior properties as compared to pure HAP, alumina, and HAP/Al2O3. Mn-HAP showed enhanced crystallinity and grain refinement, leading to improved hardness of 1198 HV for Mn-HAP/Al2O3 as compared to 39.84 HV for pure HAP and 1028 HV for HAP/Al2O3. The friction coefficient was found to be best in the Mn-HAP/Al2O3 sample. Corrosion rate significantly decreases in Mn-HAP/Al2O3 (1.63 ± 0.28) mmpy after coating on alumina. In vitro studies demonstrated enhanced cell attachment, proliferation, and differentiation after Mn-HAP coating on alumina. Antimicrobial tests revealed improved resistance against E. coli and S. aureus, with Mn-HAP/Al2O3 showing a larger zone of inhibition. The study concludes that 3 wt% Mn-HAP coatings deposited by RF magnetron sputtering hold great promise for enhancing the performance and longevity of hard tissue implants, paving the way for advanced biomedical applications.

Unveiling high-temperature stability and growth dynamics of CVD-SiOC coatings across different deposition conditions and environments

Abstract In this study, we systematically investigated the high-temperature protection performance and evolution behavior of three different SiOC coatings (1050SiOC, 1100SiOC, 1150SiOC) under different atmospheres. The coatings were prepared by the organometallic chemical vapor deposition (CVD) method and characterized using scanning electron microscopy (SEM), grazing incidence x-ray diffraction (GIXRD), x-ray photoelectron spectroscopy (XPS) techniques. It was found that the composition and microstructure of SiOC coatings, environmental atmosphere, and heat treatment temperature can affect the thermal stability and high-temperature reaction mechanism of SiOC coatings. Further, it was revealed that the three SiOC coatings only exhibit the same high-temperature evolution behavior and reaction mechanism in an air environment while exhibiting different high-temperature evolution behavior and reaction mechanisms in both an inert atmosphere and a reduced air atmosphere. Among the coatings prepared, the 1050SiOC coating demonstrated the highest on-set oxidation temperature under identical oxygen content conditions. This characteristic may contribute to the coating’s excellent resistance to high-temperature oxidation.

One-step solution processing of printable Sb2S3 nano-rods for high-performance photoconductors

Abstract Achieving large-scale, affordable, and highly dependable production of antimony sulfide is crucial for unlocking its potential in various applications, including photoconductors, solid-state batteries, thermoelectrics, and solar cells. In our study, we introduce a straightforward, economical, and catalyst-free single-step solution process for fabricating one-dimensional Sb2S3 nanostructures on flexible polyimide substrates, and we explore their use as photoconductors in the ultraviolet (UV) and visible light spectrum. The precursor solution for creating the Sb2S3 films is prepared by dissolving specified quantities of elemental Sb and S in a solution mixture of ethylenediamine and 2-mercaptoethanol. This solution is then spin-coated onto a polyimide substrate and subsequently annealed at 300 °C for several minutes. Utilizing field emission scanning electron microscopy, grazing incidence x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we demonstrate that the Sb2S3 films possess high crystallinity, uniform morphology, and a composition that is nearly stoichiometric. Additionally, through Tauc plot analysis, we determine that the films exhibit a direct bandgap of approximately 1.67 eV, which is in close agreement with the bandgap predicted by Heyd–Scuseria–Ernzerhof (HSE06) density-functional theory simulations. The metal-semiconductor–metal photoconductors fabricated with these films display a significant photoresponse to both UV and visible light. These devices achieve a UV on/off ratio of up to 160 at a light intensity of 30 mW cm−2, with brief rise and fall times of 44 ms and 28 ms, respectively.

Enhancing corrosion fatigue performance of 17-4 PH stainless steel by simultaneous aging and plasma nitriding

This study investigated the effects of simultaneous aging and low-temperature plasma nitriding on the corrosion fatigue performance of 17-4 PH stainless steel. Plasma nitriding was conducted under two temperatures of 400 and 500 °C and, for comparison, some other specimens were subjected to aging treatment at the same temperatures and times. Microstructural characterization by scanning electron microscope (FESEM) and electron backscatter diffraction (EBSD) confirmed similar structures at the core in the nitrided and aged specimens, thereby, the influence of nitrogen at the surface of 17-4 alloy could be carefully investigated. X-ray diffraction and grazing incidence X-ray diffraction (GIXRD) identified expanded martensite as the matrix within the nitrided layer, accompanied by CrN, Fe3N, and Fe4N phases. X-ray photoelectron spectroscopy (XPS) analysis revealed high nitrogen concentration, in regions very close to the surface, after nitriding at 500 °C. The N1s spectra shifted towards lower binding energies, indicating interaction between nitrogen and the matrix atoms, and the formation of nitrides in the nitrided layer. The nitrided thicknesses experienced close values at 400 °C (10 h) and 500 °C (5 h), provided at 400 °C the layer was mostly a supersaturated solid solution but at 500 °C it was composed of iron nitrides and chromium nitride. High hardness values of above 1600 HV0.1 were obtained after optimum plasma nitriding as the result of combined effects of solution strengthening induced by nitrogen atoms and the presence of dispersed nitride phases. EBSD results indicated residual stress within the nitrided layer, which would affect the corrosion fatigue resistance. Experimental findings demonstrated that both aging and plasma nitriding substantially enhanced the corrosion fatigue resistance of 17-4 PH stainless steel in 3.5 wt% NaCl. Moreover, simultaneous aging and plasma nitriding proved superior behavior in corrosion fatigue, primarily due to delayed crack initiation and improved fatigue resistance, without the risk of overaging which is detrimental to mechanical properties.

Specific iron binding to natural sphingomyelin membrane induced by non-specific co-solutes

HypothesisSphingomyelin (SPM), a crucial phospholipid in the myelin sheath, plays a vital role in insulating nerve fibers. We hypothesize that iron ions selectively bind to the phosphatidylcholine (PC) template within the SPM membrane under near-physiological conditions, resulting in disruptions to membrane organization. These interactions could potentially contribute to the degradation of the myelin sheath, thereby playing a role in the development of neurodegenerative diseases. ExperimentsWe utilized synchrotron-based X-ray spectroscopy and diffraction techniques to study the interaction of iron ions with a bovine spinal-cord SPM monolayer (ML) at the liquid-vapor interface under physiological conditions. The SPM ML serves as a model system, representing localized patches of lipids within a more complex membrane structure. The experiments assessed iron binding to the SPM membrane both in the presence of salts and with additional evaluation of the effects of various ion species on membrane behavior. Grazing incidence X-ray diffraction was employed to analyze the impact of iron binding on the structural integrity of the SPM membrane. FindingsOur results demonstrate that iron ions in dilute solution selectively bind to the PC template of the SPM membrane exclusively at near-physiological salt concentrations (e.g., NaCl, KCl, KI, or CaCl2) and are pH-dependent. In-significant binding was detected in the absence of these salts or at near-neutral pH with salts. The surface adsorption of iron ions is correlated with salt concentration, reaching saturation at physiological levels. In contrast, multivalent ions such as La3+ and Ca2+ do not bind to SPM under similar conditions. Notably, iron binding to the SPM membrane disrupts its in-plane organization, suggesting that these interactions may compromise membrane integrity and contribute to myelin sheath damage associated with neurological disorders.

Enhancing electrical and thermal property of diamond-based Ta2N films through introducing a Ta transition layer

Diamond, renowned for its exceptional heat dissipation properties, stands out as an optimal substrate for tantalum nitride (Ta2N) film resistors. To fully exploit the high thermal conductivity of diamond, we introduce a thin tantalum (Ta) interlayer between the TaN thin film and the polished diamond substrate, aiming to strengthen their bond and enhance the interfacial thermal conductance. Comprehensive morphological and structural analyses, utilizing advanced techniques such as grazing incident X-ray diffraction (GI-XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS), were employed. Electrical properties were measured using a four-point probe, and thermal boundary conductance (TBC) between Ta2N and diamond was assessed through time-domain thermoreflection (TDTR), comparing scenarios with and without the Ta interlayer. Results demonstrate that the Ta interlayer facilitates tantalum carbide (TaxC) formation, improving adhesion and resulting in a remarkable 70 % increase in overall interface TBC. Moreover, the thin Ta interlayer positively influences the overall temperature coefficient of resistance (TCR) of the Ta2N film. Our strategic approach showcases enhanced adhesion and thermal performance, opening promising avenues for elevated functionality and reliability of Ta2N film resistors in high-temperature applications.

The Influence of Ag Addition and Different SiO2 Precursors on the Structure of Silica Thin Films Synthesized by the Sol-Gel Method.

In this work, the structure of silica thin films synthesized with three different SiO2 precursors and obtained by the sol-gel method and dip coating technique was studied. Additionally, the influence of Ag addition on the obtained silica sols and then gel structure was investigated. Silica coatings show antireflective properties and high thermal resistance, as well as hydrophobic or hydrophilic properties. Three different silica precursors, TEOS (tetraethylorthosilicate), DDS (dimethyldietoxysilane) and AerosilTM, were selected for the synthesis. DDS added to silica sol act as a pore size modifier, while Ag atoms are known for their antibacterial activity. Coatings were deposited on two different substrates: steel and titanium, dried and annealed at 500 °C in air (steel substrate) and in argon (titanium substrate). For all synthesized films, IR (infrared) spectroscopic studies were performed together with GID and XRD (Grazing Incidence Diffraction, X-ray Diffraction) measurements. The topography and morphology of the surface were traced by SEM and AFM microscopic methods, providing information on the samples' roughness, particle sizes and thickness of the particular layers. The wetting angle values were also measured. GID and XRD measurements pointed to the distinct contribution of an amorphous phase in the samples, allowing us to recognize the crystalline phases and calculate the silver crystallite sizes. The FTIR spectra gave information on the first coordination sphere of the studied samples.

Engineering wafer scale single-crystalline Si growth on epitaxial Gd2O3/Si(111) substrate using radio frequency sputtering for silicon on insulator application

Silicon on Insulator (SOI) technology has been the promising solution for the On-chip low-power mixed-signal systems. However, the traditional smart-cut method for SOI wafer fabrication is costly. Hence, in this work, we present an optimized methodology to fabricate a wafer scale single-crystalline Si on epitaxial Gd2O3/Si(111) substrate (SOXI) using a low-cost, high volume manufacturable (HVM)-friendly Radio Frequency magnetron sputtering technique for SOI application. The grown Si and Gd2O3 layers are physically characterized using high-resolution X-ray Diffraction and high-resolution Transmission Electron Microscopy (HRTEM). The Grazing Incidence X-ray Diffraction, Pole Figure, and HRTEM imaging confirm the formation of an epitaxial Top-Si layer on the epitaxial-Gd2O3/Si(111) substrate. Hence, we demonstrate a low-cost, HVM-friendly technique for the fabrication of SOXI wafers.

Oxidation of lipid membrane cholesterol by cholesterol oxidase and its effects on raft model membrane structure

The effects of a peripheral protein – cholesterol oxidase (3β-hydroxysteroid oxidase, ChOx) on the characteristics of model lipid membranes composed of cholesterol, cholesterol:sphingomyelin (1:1), and the raft model composed of DOPC:Chol:SM (1:1:1) were investigated using two membrane model systems: the flat monolayer prepared by the Langmuir technique and the curved model consisting of liposome of the same lipids. The planar monolayers and liposomes were employed to follow membrane cholesterol oxidation to cholestenone catalyzed by ChOx and changes in the lipid membrane structure accompanying this reaction. Changes in the structure of liposomes in the presence of the enzyme were reflected in the changes of hydrodynamic diameter and fluorescence microscopy images, while changes of surface properties of planar membranes were evaluated by grazing incidence X-ray diffraction (GIXD) and Brewster angle microscopy. UV-Vis absorbance measurements confirmed the activity of the enzyme in the tested systems. A better understanding of the interactions between the enzyme and the cell membrane may help in finding alternative ways to decrease excessive cholesterol levels than the common approach of treating hypercholesterolemia with statins, which are not free from undesirable side effects, repeatedly reported in the literature and observed by the patients.

High-sensitive and fast-responsive In2O3 thin film sensors for dual detection of NO2 and H2S gases at room temperature

In this work, the room-temperature dual gas sensing characteristics of indium oxide (In2O3) thin films towards NO2 and H2S have been studied. In2O3 thin films were synthesized by the thermal oxidation of indium metal films of various thicknesses in the range of 50–250 nm deposited by thermal evaporation method. Grazing incidence X-ray diffraction (GI-XRD) revealed the change in preferred orientation of In2O3 thin films corresponding to varying thickness, while field-emission electron microscopy studies showcased evolving surface morphologies from individual grains to granular network with respect to the increase in film thickness. Investigations were made on the ability of In2O3 thin films to detect various low concentrations of nitrogen dioxide (NO2) and hydrogen sulfide (H2S) gases at ambient temperature. In2O3 thin films synthesized using 100 nm thick In films exhibited good sensing response of around 58 and 68 % towards NO2 and H2S gases of 5 ppm respectively, at room temperature (27 °C) with the response time of 36 and 18 s. Remarkably, the lower experimental detection limit of these toxic gases could be extended up to 100 ppb. Using X-ray photoelectron spectroscopy, a large presence of surface oxygen is observed on the In2O3 thin film. The sensor has demonstrated remarkable sensing abilities, including strong selectivity, quick sensing response, and good repeatability.

Spin reorientation transition in epitaxial nanometric Nd-Fe-B films with large perpendicular magnetic anisotropy

The development of hard magnetic properties in Nd-Fe-B films with a thickness below 50 nm has been studied and the effect of the film strain on the spin reorientation transition temperature (TSR) evaluated. A value of 35 nm is found to be the lowest thickness threshold in the films grown by DC magnetron sputtering in this study for the full development of both the Nd2Fe14B phase and the broadening of the out of plane hysteresis loops. Large perpendicular magnetic anisotropy is obtained for a film of 40 nm in thickness, reaching a coercivity of 8 kOe at room temperature. A detailed characterization of epitaxial Nd2Fe14B with high magnetic anisotropy has been done by Grazing Incidence X-Ray Diffraction, lattice parameters are reported and the chemical states of Nd 3d and Fe 2p have been stablished by the analysis of Hard X-Rays Photoelectron Spectroscopy spectra. The spin reorientation transition temperature has been estimated to a value of 124.2 K. Based on experimental results, lattice strain is attributed as the main reason for the deviation of TSR by comparison with the theoretical value (135 K). No evidence of tetragonal distortion in the lattice is found below TSR in this system in contrast to previous considerations.

Spin-transport across semi-crystalline polyvinylidene fluoride thin films in Ta/Co/PVDF/NiFe pseudo spin-valve devices

Room temperature magnetoresistance (MR) across semi-crystalline polyvinylidene fluoride (PVDF) thin films in Ta(2 nm)/Co(15 nm)/PVDF/NiFe(28 nm) pseudo-spin-valve devices (PSVs) are systematically investigated by varying PVDF thicknesses from 80 − 230 nm and applied bias voltages up to 100 mV. NiFe, Ta/Co magnetic bottom and top electrodes, and PVDF thin films are deposited by DC magnetron sputtering and spin-coating methods. The structural, microstructural, and magnetic natures have been evaluated using grazing incidence X-ray diffraction, atomic force microscopy, and magneto optic kerr effect systems. Electrical characteristics reveal a maximum MR of ∼0.25 % at 60 mV bias voltage across PVDF-80 nm and ∼0.08 % across PVDF-230 nm & PVDF- 120 nm devices. A constant MR is found across all the devices up to 100 mV applied bias voltages. In addition to the electrical spin injection evaluation, coplanar waveguide ferromagnetic resonance measurements are utilized to validate the spin injection into PVDF layers by estimating the Gilbert damping parameters of NiFe and PVDF/NiFe bilayers. Furthermore, low MR in PSVs is discussed with the parallel spin-dependent conducting channels corresponding to PVDF’s amorphous, alpha, and beta crystalline phases.

Impact of deposition pressure on the structural, nanomechanical, and tribological properties of δ-TaN coatings deposited via magnetron sputtering on Ti6Al7Nb alloy

In the present study, δ-TaN thin films were deposited by reactive magnetron sputtering (physical vapour deposition) on Ti6Al7Nb alloy by varying the deposition pressure (0.8–0.2 Pa). Their crystalline structure, chemical composition, surface roughness, and surface morphology were investigated by using grazing incidence X-ray diffraction, energy dispersive spectroscopy, scanning probe microscope, and field emission scanning electron microscopy (FESEM), respectively. Structural analysis results confirmed the deposition of cubic δ-TaN thin films along the (111) basal plane; moreover, spherical dome-like surface morphology was observed by FESEM. Further, to analyze the nanomechanical properties of the deposited δ-TaN coatings, such as hardness (H) and modulus (E), scratch tests were performed utilizing the nanomechanical system. Moreover, friction and wear properties of the coating and bare sample (substrate) were investigated on nano-tribometer equipment using a rotary ball-on-disk type configuration. The stainless steel (SS-316) and silicon nitride (Si3N4) balls were used as the counter materials for the tribological tests. The observations of nanomechanical tests revealed that H (GPa), E (GPa), and H/E ratio values increased from 11.83 to 28.30 GPa, 176.02 to 248.45 GPa, and 0.06 to 0.11, respectively, with the decrease of the deposition pressure. In the scratch test, the highest critical load (cohesion failure) was found for δ-TaN coating deposited at the lowest deposition pressure (0.2 Pa). Tribological results of δ-TaN coatings demonstrated average coefficient of friction (COF) value ranges between 0.066–0.092 and 0.072–0.029 against steel and Si3N4 balls, respectively. The wear rate values were observed to vary from 8.15 × 10−5 to 7.56 × 10−6 and from 1.77 × 10−3 to 8.99 × 10−6 against steel and Si3N4 balls, respectively. Generally, the average COF and wear rate decreased against 316 SS and Si3N4 balls as the deposition pressure of coatings decreased. However, the coating deposited at 0.8 and 0.6 Pa against Si3N4 ball showed early delamination of the coating, resulting in the sudden fluctuation in COF plots and higher wear rate in the range of 10−3 mm3/N.m.

High-Performance Semiconducting Carbon Nanotube Transistors Using Naphthalene Diimide-Based Polymers with Biaxially Extended Conjugated Side Chains.

Polymer-wrapped single-walled carbon nanotubes (SWNTs) are a potential method for obtaining high-purity semiconducting (sc) SWNT solutions. Conjugated polymers (CPs) can selectively sort sc-SWNTs with different chiralities, and the structure of the polymer side chains influences this sorting capability. While extensive research has been conducted on modifying the physical, optical, and electrical properties of CPs through side-chain modifications, the impact of these modifications on the sorting efficiency of sc-SWNTs remains underexplored. This study investigates the introduction of various conjugated side chains into naphthalene diimide-based CPs to create a biaxially extended conjugation pattern. The CP with a branched conjugated side chain (P3) exhibits reduced aggregation, resulting in improved wrapping ability and the formation of larger bundles of high-purity sc-SWNTs. Grazing incidence X-ray diffraction analysis confirms that the potential interaction between sc-SWNTs and CPs occurs through π-π stacking. The field-effect transistor device fabricated with P3/sc-SWNTs demonstrates exceptional performance, with a significantly enhanced hole mobility of 4.72 cm2 V-1 s-1 and high endurance/bias stability. These findings suggest that biaxially extended side-chain modification is a promising strategy for improving the sorting efficiency and performance of sc-SWNTs by using CPs. This achievement can facilitate the development of more efficient and stable electronic devices.

Influence of deposition pressure on microstructure, mechanical and electrical properties of niobium thin films

Niobium (Nb) thin films were deposited on a Si substrate using magnetron sputtering system by varying the deposition pressure. The effect of deposition pressure on the microstructure, residual stresses, and electrical properties was investigated by systematically varying the deposition pressure from 0.15 to 0.60 Pa. The Nb thin films were characterized using hard x-ray reflectivity, grazing incidence x-ray diffraction, four point probe method, and atomic force microscopy. The films grown at lower deposition pressures had smooth surfaces and more compact structures, which are advantageous for lowering electrical resistance but had higher compressive stress. On the other hand, the films grown at higher deposition pressures had columnar type growth with less dense structures, which leads to increase in electrical resistance. However the nature of stresses transform from compressive to tensile. Hard X-ray reflectivity performed on Nb films provides direct insight into the growth and the microstructure which were correlated with the mechanical and electrical properties.

Microstructural investigation of Au ion-irradiated Eu-doped LaPO4 ceramics and single crystals

Ceramics and single crystals of LaPO4 monazite doped with Eu(III) were irradiated with 14 MeV Au5+ ions at three different fluences. Changes to crystallinity, local coordination environments, and topography were probed using grazing-incidence X-ray diffraction (GIXRD), vertical scanning interferometry (VSI), scanning electron microscopy (SEM), Raman, and luminescence spectroscopy. GIXRD data of the ceramics revealed fluence dependent amorphization. A similar level of amorphization was detected for samples irradiated with 5 × 1013 ions/cm2 and 1 × 1014 ions/cm2, whereas the sample irradiated with the highest fluence of 1 × 1015 ions/cm2 appeared slightly less amorphous. VSI showed clear swelling of entire grains at the highest ion fluence, while more localized damage to grain boundaries was detected for ceramic samples irradiated at the lowest fluence. Single crystal specimens showed no pronounced topography changes following irradiation. SEM images of the ceramic irradiated at the highest fluence showed topological features indicative of grain surface melting. Raman and luminescence data showed a different degree of disorder in polycrystalline vs. single crystal samples. While changes to PO4 vibrational modes were observed in the ceramics, changes were more subtle or not present in the single crystals. The opposite was observed when probing the local Ln-O environment using Eu(III) luminescence, where the larger changes in terms of an elongation of the Eu-O (or La-O) bond and an increasing relative disorder with increasing fluence were observed only for the single crystals. The dissimilar trends observed in irradiated single crystals and ceramics indicate that grain boundary chemistry likely plays a significant role in the radiation response.

A novel water-in-deep eutectic solvent microemulsions for chemical polishing of single crystal KDP

Microemulsion (ME) has been investigated as a chemical polishing (CP) fluid for effective polishing of single crystal potassium dihydrogen phosphate (KDP), perfectly avoiding the generation of mechanical stress. In this work, a water-in-deep eutectic solvent ME was proposed as the polishing fluid for CP of single crystal KDP. Deep eutectic solvent (DES) is formulated using n-octanol as hydrogen bond donor and methyltrioctylammonium chloride (MTOAC) as hydrogen bond acceptor, with a mass ratio of 2:1. The ME was prepared by mixing DES as the oil phase (12.5 %, wt.), a hydrochloric acid solution as the water phase (12.5 %, wt.), and isopropanol as the cosolvent (75 %, wt.), without adding any other surfactants. The properties of the ME were characterized by conductivity measurements and ultraviolet (UV) spectroscopy. The reactivity of ME with KDP was measured by the conductivity method, and it was higher at low pH values. A hydrochloric acid solution with a pH of 3 was selected as aqueous phase, considering its effects on particle size, salt loading, and static etching rate. The water content affects the polarity of ME and the final water content was determined to be 12.5 % to ensure high polarity of ME. The surface quality of the KDP crystals before and after polishing was examined using grazing incidence X-ray diffraction (GIXRD) analysis. The average roughness of the KDP crystal surface was decreased from 1.96 nm to 1.43 nm, and the root-mean-square (RMS) roughness was reduced from 2.81 nm to 1.86 nm, demonstrating a significant polishing effect. Finally, the polishing mechanism was elucidated in terms of the irreversible chemical reaction between the active components in the microemulsion and the KDP crystals.