Grazing Incidence X-ray Diffraction Research Articles

Maximizing Quantum Hole Collection on Anatase TiO2 Thin Films with (001) Facets for Photoelectrochemical Oxigen Evolution Reaction Efficiency

Hydrogen production from water, a key element in the renewable energy portfolio, offers a solution to reduce reliance on fossil fuels. Photoelectrochemical (PEC) hydrogen production, using light-absorbing semiconductors and catalysts, offers a clean and cost-effective method for harnessing solar energy. To enhance the efficiency of PEC, this study explores the use of anatase TiO2 thin film photoelectrodes as an alternative to expensive and rare catalysts, aiming to generate hydrogen as a clean fuel with oxygen as a byproduct.Anatase titanium dioxide is a well-established functional material widely applied in the fields of environment and energy. Recognized as one of the premier materials for photocatalysis and a promising photoanode material for water splitting, titanium dioxide (TiO2) finds use in diverse applications such as dye-sensitized solar cells, perovskite-based solar cells, and cleaning devices. Its band gap of 3.2 eV, stability, strong absorption in the UV region, and energetics of the valence and conduction band edges make anatase particularly suitable for PEC water splitting, especially for the oxygen evolution reaction (OER).Our research focuses on the development of anatase thin films with strong [001] texture and (001) facets at the surface of the film. The (001) facets are known to accumulate photogenerated hole states while the [001] orientation imparts a negative flat band potential. We hypothesize that these two properties, (001) facets and [001] texture, are ideal for OER. This study combines these two structural characteristics within the semiconductor TiO2 layer to enhance PEC performance and maximize the efficiency of hole collection during water oxidation.Anatase TiO2 thin films with (001) facets and [001] orientation were hydrothermally synthesized on a fluorine-doped tin oxide (FTO) substrate and annealed at 500°C. The films exhibited [001] orientation and (001) faceting as shown by grazing incidence X-ray diffraction (GI-XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Photoelectrochemical measurements via cyclic voltammetry in a 0.1 M KOH and Na2SO3 solution demonstrated the films' hole collection efficiency under a 365 nm UV light source. The photoelectrochemical (PEC) and oxygen evolution reaction (OER) characteristics of anatase thin films were observed both under dark and light conditions. Prior to illumination, only the Ti3+/Ti4+ redox couple was observed with an onset potential of 0.01 V (RHE) and negligible OER at anodic potentials. When UV irradiated, the TiO2 thin films exhibited a photocurrent that increased through the anodic scan. The onset potential of photocurrent, measured in the presence of the hole scavenger, exhibited a negative shift ranging from -100 to -200 mV compared to the KOH onset potential. This shift is attributed to the film surface's limited efficiency in collecting holes for water oxidation at low potentials, as rapid recombination kinetics compete with water oxidation. Interestingly, the photocurrent observed with Na2SO3 electrolyte was 0.15 to 0.3 times more than what we saw with KOH electrolyte. Our preliminary results indicate a current density of ~2.0-2.5 mA cm-2 at 1.8 V and a hole collection efficiency of ~84 % at 1.23 V vs RHE, the thermodynamic water oxidation potential. In summary, we have made significant progress toward enhancing the PEC activity of anatase TiO2 thin films by optimizing the film structure for both reactivity and charge transport.

Material Changes of Bimetallic Ag–Cr, Fe, Co, Ni, Cu, Sn Electrocatalysts during Alkaline Oxygen Reduction in Fundamental Versus Alkaline Membrane Exchange Fuel Cell Conditions

The more apparent challenges of climate change drastically increase the global demand for sustainable fuel production and usage.1 In this context, hydrogen fuel cells (FCs) powered by renewable electricity are among the promising technologies.2 Addressing the sluggish cathode reaction in FCs, the oxygen reduction reaction (ORR), these devices hold immense potential for sustainable energy conversion and storage. An alkaline environment allows for the utilization of more abundant and cost-effective metals in contrast to current platinum-based catalysts. Silver (Ag), for instance, exhibits high selectivity for the ORR, i.e., forming hydroxide instead of peroxide.3 When combined with secondary metals, bimetallic Ag catalysts show enhanced activity, making them viable alternatives to platinum-group materials for ORR.In our highly collaborative research, we investigated the material transformations of bimetallic Ag thin films with chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and tin (Sn) as secondary metals for ORR electrocatalysis in fundamental rotating disk electrode (RDE) setups and the application device, anion-exchange membrane FC (AEMFC). Grazing-incidence X-ray diffraction (GI-XRD) conducted prior to electrochemical testing reveals no evidence of alloying except for the Ag-Sn bimetallic thin film. However, X-ray photoelectron spectroscopy (XPS) indicates a shift of the Ag 3d peaks to higher binding energies for all catalysts, suggesting a hybridization of Ag and the secondary metals. The composition of the metal surface, native oxide formation, ORR performance, and material changes post-RDE testing vary distinctly among the Ag bimetallic catalysts depending on the secondary metal. Intriguingly, performance is either enhanced (Ag-Co, Ag-Sn), maintained with reduced Ag content (Ag-Fe, Ag-Cr), or falls in between the two monometallic materials (Ag-Ni) compared to monometallic Ag thin films. Density functional theory (DFT) calculations offer insights into the catalyst performances and changes in metal oxidation states and surface composition prior and post electrocatalysis. AEMFC tests reveal promising performances under device conditions contradicting our fundamental RDE measurements. The integration of fundamental and application device tests, along with material characterization and DFT calculations, enables a comprehensive exploration of material changes under varying electrochemical conditions. This underscores the complexity of bimetallic catalysts and the importance of testing under device conditions, positioning Ag-bimetallic catalysts as highly promising alternatives to platinum-group metal catalysts for alkaline ORR.

Redox Stability Analysis of Co-Doped Barium Niobate Thin Films Via Cyclic Voltammetry

The electrochemical oxidative coupling of methane (E-OCM) to higher hydrocarbons, requires anodes that are stable under reducing conditions. We have previously demonstrated high activity with long term stability/durability for the perovskite anode BaMg0.33Nb0.67-xFexO3-δ (BMNF) while performing E-OCM1. Our group has also improved the total conductivity and activity of barium niobate perovskites via exchange of Mg for Ca (from 18 mS/cm-1 to 41 mS/cm-1), while also decreasing the Goldschmidt tolerance factor below 1 for increased cubic perovskite structural stability2. Perovskite metal oxide thin films can be produced with well-defined thicknesses and stoichiometries through pulsed laser deposition (PLD)3. These thin films are utilized in cyclic voltammetry experiments on YSZ substrates to further elucidate the chemical stability and oxygen sub-stoichiometry of high temperature SOFC/SOEC electrodes. Through application of reducing potentials to the electrode of interest, the voltage and current responses can be correlated to effective oxygen activities in which reduction of the electrode may occur. Usage of this technique with calcium and iron doped barium niobate perovskites (BaCa0.33Nb0.67-xFexO3-δ - BCNF) provides insights into the thermochemical stability and iron doping effects under highly reducing environments. The BCNF thin film electrodes were characterized via grazing incidence XRD and XRF for crystal structure and chemical composition. After initial characterization, cyclic voltammetry experiments were performed in a novel cell setup. These BCNF thin films show promise for evaluating stability mechanisms for E-OCM operation while providing details on compositional changes and oxygen loss of BCNF in reducing environments.

(Invited) Role of Oxidant Gas for Atomic Layer Deposition of HfxZr1−XO2 Thin Films on Ferroelectricity of Metal-Ferroelectric-Metal Capacitors

Since the first report of ferroelectricity in HfxZr1−xO2 (HZO) in 2011 [1], a lot of attention has been devoted for future non-volatile memory device applications due to its scalability (< 10 nm), low thermal budget (< 400°C) and matured atomic layer deposition (ALD) technique [2]. The thermal ALD process using H2O or O3 is generally employed for the fabrication of ferroelectric HZO thin films. On the other hand, the effect of the plasma-enhanced ALD process using O2 plasma gas on the crystallinity and ferroelectricity has not been systematically clarified. In this paper, we report the importance of ALD oxidant gases for HZO films using H2O or O2 plasma on the ferroelectricity of metal–ferroelectric–metal (MFM) capacitors.MFM capacitors with the H2O- and O2 plasma-based HZO films were fabricated as follows. A 10-nm-thick HZO films were deposited on a TiN bottom-electrode (BE-TiN) by ALD at 300°C using H2O or O2 plasma as oxidant gases and (Hf/Zr)[N(C2H5)CH3]4 (Hf:Zr = 1:1) cocktail precursor. The Hf/Zr ratios in both types of HZO films were estimated to be 0.4/0.6 using X-ray photoelectron spectroscopy (XPS). Next, a post-deposition annealing (PDA) process was carried out at 400 °C for 1 min under a N2 atmosphere. Finally, a TiN top-electrode was deposited by DC sputtering.First, the crystallinity and remanent polarization (2P r = P r + − P r −) of the H2O- and O2 plasma-based HZO films were investigated. Nanocrystals with ferroelectric orthorhombic (O), tetragonal (T), cubic (C) phases partially existed in the O2 plasma-based film after the ALD process, while an amorphous structure dominantly existed in the H2O-based film, analyzed by the grazing-incidence X-ray diffraction analysis and cross-sectional transmission electron microscopy images [3]. This could be because of a strong oxidation power and high energy ion/electron bombardment of O2 plasma. After the PDA process, the O phase was formed more in the O2 plasma-based HZO film than the H2O-based film. Therefore, the nanocrystal grains in the as-grown O2 plasma-based HZO film could play an important role as nuclei for the crystallization and formation of O phase [3,4]. From the polarization–electric field hysteresis curves, the PDA-treated O2 plasma-based capacitor exhibited 2P r of 20 µC/cm2, which was 1.5 times higher than that (13 µC/cm2) of the H2O-based capacitor. Thus, these results indicate that the crystallization and O phase formation of HZO films were promoted by using O2 plasma gas as an ALD oxidant, resulted in a higher 2P r.Next, endurance properties of these MFM capacitors were evaluated. In the wake-up state, both capacitors showed almost the same increase rate (~8%) of switching polarization (P sw). In the fatigued state, on the other hand, the O2 plasma-based capacitor exhibited less P sw degradation (~33%) after 106 cycles, whereas the P sw of H2O-based capacitor decreased by ~47%. To clarify these different fatigue properties, the TiOxNy interface reaction layer (IRL) formation at the HZO/BE-TiN interface was analyzed using synchrotron hard X-ray photoelectron spectroscopy (HAXPES). For the HAXPES Ti 2p spectra, the Ti-O peak intensity for the O2 plasma-based capacitor was larger than that of the H2O-based capacitor [5]. Therefore, an oxygen-rich TiON-IRL could be formed at the HZO/BE-TiN interface during ALD process due to the stronger oxidizing power of O2 plasma. Additional oxygen vacancies (VO) were reported to formed in HfO2-based films during field cycling due to the interface reaction between the HfO2-based film and TiN electrode. Moreover, one of the origins of the P sw degradation was thought to be domain pinning caused by VO [6]. Therefore, an oxygen-rich TiON-IRL for the MFM capacitor with the O2 plasma-based HZO film could prevent the interface reaction and formation of additional VO in HZO films, led to superior fatigue properties.In summary, the MFM capacitor with the O2 plasma-based HZO film showed superior 2Pr and fatigue resistance compared to those of the H2O-based one. Based on these experimental results, it is important to consider the selection of an ALD oxidant for fabrication of HZO-based MFM capacitors.This work was partly supported by JSPS KAKENHI (Nos. JP21J01667, JP20H02189, and JP18J22998) and MEXT Leading Initiative for Excellent Young Researchers (No. JPMXS0320220213). The HAXPES measurements were performed under approval of the NIMS Synchrotron X-ray Station (2020A4602 and 2020A4651).[1] J. Müller et al., Appl. Phys. Lett. 99, 112901 (2011).[2] J.-H. Kim et al., ACS Appl. Electron. Mater. 5, 4726 (2023).[3] T. Onaya et al., APL Mater. 10, 051110 (2022).[4] T. Onaya et al., Microelectron. Eng. 215, 111013 (2019).[5] T. Onaya et al., Solid State Electron. 210, 108801 (2023).[6] M. Pešić et al., Adv. Funct. Mater. 26, 4601 (2016).

Impact of Residual Strains on the Carrier Mobility and Sability of Perovskite Films.

Solution-based inorganic-organic halide perovskites are of great interest to researchers because of their unique optoelectronic properties and easy processing. However, polycrystalline perovskite films often show inhomogeneity due to residual strain induced during the film's post-processing phase. In turn, these strains can impact both their stability and performance. An exhaustive study of residual strains can provide a better understanding and control of how they affect the performance and stability of perovskite films. In this work, we explore this complex interrelationship between residual strains and electrical properties for methylammonium CH3NH3PbI3-xClx films using grazing incidence X-ray diffraction (GIXRD). We correlate their resistivity and carrier mobility using the Hall effect. The sin2(ψ) technique is used to optimize the annealing parameters for the perovskite films. We also establish that temperature-induced relaxation can yield a significant enhancement of the charge carrier transports in perovskite films. Finally, we also use Raman micro-spectroscopy to assess the degradation of perovskite films as a function of their residual strains.

Unveiling the secrets of non-evaporable getter films: Activation temperature, activation time, and achievable activation degree

Non-evaporable getter films play an important role in the creating and maintaining of high or ultra-high vacuum environments in advanced scientific disciplines. Prior to application, thermal activation in a vacuum environment is essential. Despite numerous attempts to reduce the film activation temperature, uncertainty remains as to whether extending the activation time at a relatively lower activation temperature will ensure a fully-activated state of the film. To address this issue, the microstructure and activation performance of the film has been investigated. Techniques, such as scanning electron microscopy, grazing incidence X-ray diffraction, energy dispersive spectroscopy, and in-situ X-ray photoelectron spectroscopy were employed. Experimental investigations show that a fully-activated state of the film cannot be achieved at around 150°C, regardless of the activation time. Further analysis shows that, at activation temperatures below about 200°C, the migration trend of oxygen atoms within TiZrV/TiZrHfV films exhibits asynchronous features. This process was accompanied by boundary effects of foreign atom migration channels. In addition, the achievable activation degree of the film shows a step characteristic. These results improve the understanding of the relationship between activation temperature, activation time, and the achievable activation degree of the film.

Electrosynthesis-Induced Pt Skin Effect in Mesoporous Ni-Rich Ni-Pt Thin Films for Hydrogen Evolution Reaction.

A Pt skin effect, i.e., an enrichment of Pt within the first 1-2 nm from the surface, is observed in as-prepared electrodeposited Ni-rich Ni-Pt thin films. This effect, revealed by Rutherford backscattering (RBS), is present for both dense thin films and mesoporous thin films synthesized by micelle-assisted electrodeposition from a chloride-based electrolyte. Due to the Pt skin effect, the Ni-rich thin films show excellent stability at the hydrogen evolution reaction (HER) in acidic media, during which a gradient in the Pt/Ni ratio is established along the thickness of the thin films, while the activity at the HER remains unaffected by this structural change. Further characterization by elastic recoil detection with He ions analysis shows that hydrogen profiles are similar to those of Pt: a surface hydrogen peak coincides with the Pt skin, and a gradient in hydrogen concentration is established during HER in acidic media, together with a considerable uptake in hydrogen. A comparative study shows that in alkaline media, hydrogen evolution has little to no effect on the structural properties of the thin films, even for much longer times of exposure. The mesoporous thin films, in addition to their higher efficiency at HER compared to dense thin films, also show lower internal stress, as determined by Rietveld refinement of grazing incidence X-ray diffraction patterns. The latter also reveal a fully single-phase and nanocrystalline structure for all thin films with varying Ni contents.

Study on the charge transport behaviour of mxene- polymer nanocomposite-based self-assembled floating films at the air-liquid interface

This study explores the fabrication and charge transport behavior of MXene-polymer nanocomposite-based self-assembled floating films at the air-liquid interface. Utilizing ultrasonic dispersion of MXene nanosheets was integrated into a DPP-TTT polymer matrix, significantly enhancing the alignment and crystallization of the polymer chains. The films were fabricated using a unidirectional floating film transfer method (UFTM), which proved to be both simple and cost-effective. UV–visible and grazing incidence X-ray diffraction (GIXD) analyses confirmed increased π–π stacking and improved structural arrangement within the nanocomposites. Organic field-effect transistors (OFETs) fabricated from these films demonstrated that a 3% MXene inclusion resulted in the highest mobility, measuring 3.1 cm2V-1s-1 with an on-off ratio in the order of 104, compared to 1.3 cm2V-1s-1 in pristine DPP-TTT films. However, further increases in MXene content reduced mobility, emphasizing the importance of precise compositional tuning.

Direct Laser Writing Crystal Polymorphs of Organic Semiconductors for Phase Change Electronics.

The many diverse polymorphic behaviors observed in organic electronic materials offer opportunities to modulate electronic properties through reversibly switching crystal structures. Here, we access the prolific polymorphism observed in two-dimensional quinoidal terthiophene via laser writing to locally heat and direct the phase transitions. We access a metastable polymorph IV through rapid cooling and observe distinct symmetry as well as packing through grazing incidence X-ray diffraction (GIXD). Using our open-source PolyChemPrint patterning platform, we direct laser heating to initiate the IV-I transition, switching the conductance by >2 orders of magnitude. This is confirmed via a combination of GIXD and Raman spectroscopy. Finally, we demonstrate switching of transistor devices as well as discrete tuning of conductance via laser writing.

Influence of topography on nano-mechanical properties of cylindrical magnetron sputtered TiN films

Numerous studies on Nano-mechanical behavior of the thin films explained primarily in terms of their film morphology and particle size rather than film topography. Therefore, the current study investigates the effect of film topography on the nano-mechanical characteristics of the film. Ti/TiN multilayer thin films were deposited at varying deposition pressures by using an indigenously developed Cylindrical Magnetron Sputtering (CMS) unit. Surface crystallographic information is characterized by synchrotron-based Grazing Incidence XRD analysis. Film growth follows self-assembled nano hill architecture as revealed by AFM and in situ Scanning Probe Microscopy images. The tribo-mechanical properties of the film is dependent on the height and spacing of its self-assembled structure, which experiences either crushing or buckling under the indenter load, thereby affecting film characteristics. Film deposited at moderate pressure exhibits superior wear behavior, attributed to the interplay between Plasticity Index (PI) and Depth Recovery Ratio (DRR). The study primarily focused on film growth phenomena by using cylindrical targets and their influence on nanomechanical properties of the film.

Fabricating Cu2Zn(SnxGe1-x)Se4 thin-film solar cells with back surface Ge grading by magnetron sputtering

In this paper, an approach of forming a band gap gradient by depositing a layer of Ge between the Mo layers by magnetron sputtering is proposed. The diffusion depth of the Ge into Cu2ZnSnSe4 (CZTSe) thin film can be effectively controlled by the Mo transition layer, resulting in the formation of Cu2Zn(SnxGe1-x)Se4 (CZTGSe) thin film with a band gap grading along the back surface. To validate the formation of the Ge gradient in the absorber, energy dispersive spectrometer line scanning and grazing incidence X-ray diffraction were performed. Furthermore, the impact of Ge layer on the morphologies of CZTSe was assessed using scanning electron microscopy. As a result, the introduced Ge layer formed a Ge grading along the back surface and improved the crystal quality of the absorber. Compared to CZTSe solar cells, the power conversion efficiency (PCE) of CZTGSe solar cells with a Ge gradient improved from 5.79 % to 9.28 %.

Deposition pressure-controlled phase tailoring and stability of β-W for spintronic applications

Understanding the nucleation and growth of tungsten (W) is technologically important in spin-to-charge interconversion for realizing energy-efficient spintronic devices. Here, we have systematically investigated the effect of Ar deposition pressure (PAr) on the nucleation and growth of W. The observed surface topography as a function of PAr reveals a microstructural transition from zone T to zone 1 in the structure zone model. The physical origin for the increasing roughness as a function of PAr correlates with the surface diffusion of adatoms and growth kinetics in the Volmer–Weber growth mechanism. Grazing incidence x-ray diffraction (GIXRD) results show that W exhibits a structural phase transition from a mixed phase of (α+β)-W to a single phase of β-W as a function of PAr. The analysis of the electron diffraction patterns obtained from the films grown on amorphous-SiNx windows also supports these observations. The observed transition is fundamentally correlated with the growth kinetics in zone T and zone I. Thickness-dependent GIXRD results qualitatively prove that the film grown in zone T exhibits compressive strain, whereas that grown in zone I exhibits only tensile strain. The critical thickness for the phase transition is strongly attributed to the strain during nucleation and growth. The increasing resistivity as a function of PAr corroborates the change in structural phases. Thickness-dependent resistivity measurements correlate with the degree of crystallinity via relative intensity observed from the GIXRD results. Our results strongly suggest that W structural phases can be deterministically controlled via PAr for developing low-power spintronic devices.

Exploring the performance of Co/Al2O3–ZrO2 nanocatalysts developed through the thermal evaporation method in dry reforming of methane

Abstract This study aimed to investigate the performance of the thin layer nanostructures of Co/Al2O3–ZrO2 in the dry reforming of methane (DRM) in a microchannel reactor. The nanostructures were prepared via utilizing the thermal evaporation method. Reactor tests were carried out at various coating times of 2, 3, and 4 min and temperatures of 700, 750, and 800 °C with a feed flow rate of 10 ml/min and a 1:1:8 ratio of helium, carbon dioxide, and methane. Also, grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) were used to identify catalyst features. According to the obtained results, the highest percentage of conversion in all samples was observed at 800 °C. The results of the reactor tests also revealed that the activity of catalyst layers highly depends on coating time. The findings demonstrated that raising deposition time improves the distribution of particle size and catalyst loading. Considering the nanostructure of Co/Al2O3–ZrO2, the sample undergoing 4 min coating time yielded the highest amount of primary methane conversion (89.3 %), primary carbon dioxide conversion (92.4 %), and H2/CO molar ratio (0.91). The stability test of the catalyst layers for 28 h at the optimum condition (P = 1 atm, T = 800 °C, t = 4 min deposition time, CH4/CO2 = 1, and GHSV = 48,000 mL g−1 h−1) showed that the catalysts prepared by this method had a good stability.

The effect of RF sputtering power on structural, nanomechanical and tribological properties of single layered TaN coatings

Single-layered TaN thin coatings were deposited on Ti6Al7Nb alloy substrates using reactive radiofrequency magnetron sputtering, with variations in target power. To assess the crystalline structure, chemical composition, and surface topography of these coatings, Grazing Incidence x-ray Diffraction (GIXRD), Energy Dispersive Spectroscopy (EDS), and Scanning Probe Microscopy (SPM) were employed, respectively. The study revealed that deposition power impacts the structure and composition of TaN coatings. Further analysis using x-ray Photoelectron Spectroscopy (XPS) indicated that the TaN coatings predominantly consisted of Ta and N, with trace amounts of oxygen (O 1s). Additionally, nanomechanical testing was conducted to evaluate hardness (H), modulus (E), and scratch properties. Results suggested that multiphase hex-TaN coatings exhibited superior H, E, and scratch properties compared to other cubic-structured TaN coatings. Friction and wear properties against steel balls under dry sliding conditions were determined using a ball-on-disk nanotribometer. The findings showed that mix-phase TaN coating exhibited a minimum coefficient of friction of 0.054 and a wear rate of 2.14 × 10−6 mm3/N.m. Abrasion, ploughing and oxidation were identified as the primary wear mechanism responsible for the wear of the TaN coatings.

Effect of Temperature on the Structure and Tribological Properties of Ti, TiN and Ti/TiN Coatings Deposited by Cathodic Arc PVD

Monolayers of Ti and TiN coatings, as well as a Ti/TiN bilayer coating, were deposited on AISI M2 steel substrates using the PVD cathodic arc technique. The coatings had a thickness close to 5 μm and an average roughness between 98.6 and 110.1 μm due to the presence of microdroplets on the surface. The crystalline structure of the materials was analyzed using Grazing Incidence X-ray Diffraction (GIXRD) with an increase in temperature to study the dynamics of oxide formation. A phase composition study was conducted using the Rietveld refinement method. At the temperatures where critical growth of titanium oxides, both anatase and rutile, was observed, pin-on-disk tests were performed to study the tribological properties of the materials at high temperatures. It was determined that the oxidation temperature of Ti is around 450 °C, promoting the formation of a combination of anatase and rutile. However, the formation of rutile inhibits the formation of anatase, which is stable above 600 °C. In contrast, TiN showed an oxidation temperature of 550 °C, with an exclusive growth of the rutile phase. The Ti/TiN bilayer exhibited mixed behavior, with the initial growth of anatase promoted by Ti, followed by the formation of rutile. Oxidation and tribo-oxidation dominated the wear behavior of the surfaces, showing a transition from mechanisms related to abrasion at low and medium temperatures to a combination of abrasion and adhesion mechanisms at high temperatures (800 °C).

Internal strain identification of seed-layered ZrO2, aluminum-, and yttrium-doped ZrO2 thin films via grazing incidence x-ray diffraction

Grazing incidence x-ray diffraction reveals that conventional post-deposition-annealed ZrO2 and in situ crystallized (by local epitaxy) ZrO2 thin films (&amp;lt;15 nm) have different internal strain states. A comparison between single- and two-step grown films enables the diverse strain components to be discretely identified. In particular, thickness-dependent intrinsic growth strain is unevenly distributed within the film according to the Volmer–Weber growth. Furthermore, extrinsic thermal strain, locally present in the annealed seed layer, does not spread over the in situ crystallized upper main layer of the two-step film. Post-deposition annealing of the two-step film renders the strain state identical to the single-step films by imposing thermal strain on the in situ crystallized main layer. Local strains created by diffused aluminum and yttrium dopants are also examined. Since each stress factor plays a vital role in the phase formation and electrical behaviors of ZrO2 and other fluorite-structure films, this method will pave the way for understanding the film's internal strain distribution and accompanying performance engineering.

Binder-free nickel/boron-doped diamond film electrodes for hydrogen evolution reaction in alkaline medium: Effect of nickel catalyst nanostructure on electrochemical performance

Boron-doped diamond (BDD) is a robust electrode material, and Ni metal is a promising alternative electrocatalyst to noble metals for promoting the hydrogen evolution reaction. In this study, binder-free Ni/BDD film electrodes, with Ni acting as a catalyst, were constructed. With thermal annealing temperature regulation, the Ni catalyst exhibited different nanostructures, including amorphous continuous films, partially crystalline corrugated films, and uniformly dispersive nanoparticles. The electrodes were characterized via scanning electron microscopy, grazing-incidence X-ray diffraction, and X-ray photoelectron spectroscopy. Furthermore, the impact of the Ni catalyst fine structure on the hydrogen evolution reaction performance was evaluated. The results highlighted the versatility of BDD as a platform for developing binder-free Ni/BDD electrodes. Through precise adjustment of the nano-scale structure of Ni catalysts on the BDD surface, high hydrogen evolution reaction activity was achieved, with an overpotential as low as 273 mV at 10 mA/cm2 in a 1 M KOH solution.

Comparative analysis of microstructural, compositional, and grazing incidence characteristics of oxide scale on 316L steel: SLM vs. wrought conditions

The aim of this research is to compare the oxidation behavior and characteristics of oxide scale of 316L steel produced by two methods: selective laser melting (SLM) and conventional casting and forming (wrought). To this end, the initial composition and microstructure of samples produced by those methods were first studied. Thermogravimetric analysis (TGA) and long-term isothermal oxidation tests were carried out on the samples and the oxidation kinetics were compared. The oxidized samples were then examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and grazing incidence X-ray diffraction (GIXRD). The results indicated that in the temperature range of 600 °C–900 °C, the oxidation resistance of the SLM alloy is lower than that of the wrought alloy, especially at 800 °C. This is attributed to the combined effect of: i) smaller grain size due to the rapid solidification in the SLM alloy that increases the paths of oxygen penetration, ii) lower presence of chromium and manganese elements in the oxide layer and iii) preferential growth of iron oxide in the form of hillocks on the surface. Surface and cross-section analysis of the oxide layers show that iron oxide is dominant on the surface of the SLM sample at temperatures of 600 °C and 800 °C, and at 800 °C its extended hilly growth leads to significant spallation of the oxide scale and an exponential increase in the oxidation rate. However, at 900 °C, with the formation of a continuous oxide layer containing Fe2MnO4 and CrMnO4, the oxidation rate significantly decreases in both alloys.

Tuning infrared emissivity of GdCoO3 thin films through Fe doping: Fabrication and mechanism

Using polymer-assisted deposition technology, GdCo1-xFexO3 (0 ≤ x ≤ 0.5) porous films with high infrared emissivity at high temperatures were prepared on Si (100) substrates. The composition and calcination temperature of the precursor are determined by TG-DSC. The structure and composition of the films are investigated using Grazing Incidence X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The surface morphology and elemental composition of the films were analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The average infrared emissivity of GdCo1-xFexO3 (0 ≤ x ≤ 0.5) films at different temperatures (100–500 °C) in the range of 8–14 μm has been tested by an infrared emissivity meter. The results show that the GdCoO3 film with Fe doping concentration of 10 % exhibits the highest infrared emissivity of 0.89 at 500 °C. Possible mechanisms for the high infrared emissivity of the films at high temperatures are discussed.

Synthesis and Modification of Boron Nitride nanotubes using ion implantation

In this work, Chemical Vapour Deposition (CVD) has been used to synthesize boron nitride (BN) nanostructures, particularly nanotubes, and selectively introduce defects into the lattice of the synthesized BN nanostructures through ion implantation. Scanning electron microscopy (SEM) images show clear evidence of BN nanostructures and BN nanotubes (BNNTs), with the latter appearing as long, thin structures with diameters ranging from ⁓30–80 nm. Raman analysis show an E2g mode of vibration assigned to hexagonal BN (h-BN) at 1366 cm−1 after ion implantation, with increased intensity. Grazing incidence X-ray diffraction (GIXRD) spectra revealed a prominent peak between 54 and 56°, corresponding to the (004) h-BN reflection, which was used to determine the average lattice parameter c⁓0.662 nm representing the stacking direction of the BN layers. The majority of the samples had broad peaks, indicative of a nanocrystalline material. The only exception was the sample grown at 1200 °C, which was found to have a Scherrer crystallite size >100 nm. In contrast, the rest of the samples had an average size of 3.5 nm. Notable observations in this study include a significant rise in the size of the Raman derived crystallite domains in the nanostructures synthesized at 1100 and 1200 °C after ion implantation with boron ions at fluence 5 × 1014 ions/cm2.