Gracing Incidence X-ray Diffraction Research Articles

INFLUENCE OF N2 FLOW RATE ON THE PROPERTIES OF VANADIUM NITRIDE THIN FILMS DEPOSITED BY REACTIVE DC MAGNETRON SPUTTERING

Vanadium nitride (VN) thin films have been deposited on silicon wafer substrates by reactive DC magnetron sputtering with varied nitrogen (N2) flow rates from 5.0 to 8.0 sccm without substrate heating. The crystallinity, morphology, and optical properties of the prepared VN films were investigated by gracing-incidence X-ray diffraction (GIXRD), field emission scanning electron microscope (FE-SEM), and UV-Vis-NIR spectrophotometer, respectively. The GIXRD pattern shows that the crystal structure of the films is consistent with the face-centered cubic VN structure. An increase in N2 led to a decrease in film thickness and sheet resistance. On the contrary, the reflectance percentage tends to increase with the increase of N2 flow rate. [Copyright information to be updated in the production process].

VLS growth of pure and Au decorated β-Ga2O3 nanowires for room temperature CO gas sensor and resistive memory applications

High-density single crystalline β-Ga2O3 nanowires on silicon (1 0 0) substrates were grown by vapour-liquid-solid growth method. We have characterized the pure β-Ga2O3 nanowires along with the Au-decorated β-Ga2O3 nanowires. The CO gas sensors at room temperature (RT) have been studied for pure and Au decorated nanowires with multiple-networked array and single nanowire devices. The diameter of the 1D nanostructure ranged from 127 ± 5 nm. The synthesized nanowires were studied using Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscope (TEM), Energy Dispersive X-ray Spectroscopy (EDS), Gracing Incidence X-ray Diffraction (GI-XRD), Photoluminescence (PL), Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). Using the Focussed Ion Beam (FIB) technique, single nanowire gas sensor devices were fabricated. Single nanowire RT CO gas sensors using the proposed Au decorated β-Ga2O3 nanowire achieved remarkable sensitivity for 100 ppm CO gas at room temperature. Besides, we have compared the RT CO gas sensing properties of multiple-networked Au decorated β-Ga2O3 nanowires with single Au-decorated β-Ga2O3 nanowire and single pure β-Ga2O3 nanowire. In addition, bipolar resistive switching property is inspected for the Au/pure β-Ga2O3 nanowires/p-Si and Au/Au decorated β-Ga2O3 nanowires/p-Si structures.

Oblique angle deposition of nanocolumnar TiZrN films via reactive magnetron co-sputtering technique: The influence of the Zr target powers

Nanocolumnar titanium zirconium nitride (TiZrN) films deposited on silicon wafer substrates were fabricated via reactive magnetron co-sputtering with oblique angle deposition (OAD) at room temperature. The influences of the sputtering power of Zr target varied from 100 to 300 W, on the structure, morphology and composition of the nanocolumnar TiZrN film were investigated by gracing-incidence X-ray diffraction (GIXRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscope (AFM) and photoelectron spectroscopy (PES). The GIXRD patterns revealed that the prepared films deposited at different sputtering powers of Zr target were crystalline in cubic phase with preferential orientation (111) and (222) planes of ZrN and TiN, respectively. The morphology obtained from FE-SEM showed well aligned slanted nanocolumnar structure, which come from the OAD technique. Increasing the sputtering power of Zr target, led to high adatom energy and enhanced collision effect during film deposition which the nanocolumnar showed obvious change in the diameter, length and tilt angle. The EDS mapping inside the nanocolumnar confirmed the homogeneity of the Ti, Zr and N element distributed in the nanocolumnar TiZrN films. Finally, the tribology behavior was preliminarily investigated based on the hardness of the nanocolumnar film and discussed in this manuscript.

Feather like highly active Co3O4 electrode for supercapacitor application: a potentiodynamic approach

This investigation focuses on the in situ preparation of cobalt oxide through a less explored potentiodynamic approach under ambient conditions. A spinel structured feather like p-type cobalt oxide is obtained having dual bandgaps. Gracing Incidence x-ray Diffraction, Raman spectroscopy, UV-Visble spectroscopy, Scanning Electron Microscope and Hall measurement are used to study the structural, optical, morphological and electrical characteristics of the film. The prepared film showed an excellent cyclic stability upto 1600 number of cycles and good charge retention as obtained from cyclic voltammetry and galvanostatic charge-discharge measurements. A high specific capacitance of 396.67 F g−1, specific energy 71.40 Wh kg−1 and specific power 10.02 kW kg−1 is obtained, implying supercapacitive nature of the material. Overall a sustainable energy storage material, prepared by template free potentiodynamic method for new generation devices has been explored in this work.

Comparative study of sensing behavior of brush coated, electrodeposited and pulsed electrodeposited Pt/GDE based amperometric hydrogen sensors

Method of deposition of Electro-catalyst plays a significant role in the sensing behavior of electrochemical sensors for hydrogen. Amperometric hydrogen sensor operating in fuel cell mode with Nafion as proton conducting electrolyte, platinum as sensing and counter electrodes has been developed. A comparative study of response behavior of hydrogen sensors with brush coated, electrodeposited and pulsed electrodeposited Pt on gas diffusion electrode (GDE) was undertaken in the concentration range of 0–4 % H2/Ar. The crystal structure and microstructure of Pt/GDE were characterized by gracing incidence X-ray diffraction and field emission scanning electron microscopy. In-situ electrochemical impedance spectroscopy was carried out for the sensors with H2/Ar at sensing electrode side. The investigations revealed that Pt/GDE fabricated by pulsed electro-deposition has better sensitivity, response time and stability compared to the brush-coated and electrodeposited Pt/GDE sensors. Improved response of sensor with Pt/GDE fabricated by pulsed electro-deposition is explained based on microstructure of Pt electro-catalyst and interfacial characteristics of electrodes with Nafion.

Optimum chemical composition of antimony sulfide selenide for thin film solar cells

Antimony sulfide (Sb2S3) with an optical bandgap (Eg) of 1.88 eV and antimony selenide (Sb2Se3) with Eg 1.1 eV, both of orthorhombic crystalline structure, offer a unique opportunity to prepare solar cell absorbers of Eg, 1.3–1.6 eV poised toward economically viable, non-toxic and ‘earth-abundant” devices. We prepared chemical precipitates of Sb-S-Se from solutions containing potassium antimony tartrate, thioacetamide and selenosulfate, which were used as sources in vacuum thermal evaporation to produce thin films (280–300 nm) of composition, Sb2SxSe3−x (x = 0.7–2). The Eg of 1.43–1.6 eV and photoconductivity, 4 × 10−5 and 8 × 10−7 Ω−1 cm−1, respectively of these films help to combine a high open circuit voltage (Voc) of 0.609 V with a conversion efficiency (η) 5.5% or a Voc of 0.503 V with η of 6.2%. A dual-crucible thermal evaporation system allowed the preparation of absorber films of varying composition (x) in the cell structure, SnO2:F (FTO)/CdS/Sb2SxSe3−x/C-Ag. The cell area were, 0.2–0.8 cm2. A prototype module of seven series-connected cells of area 1 cm2 each produced a Voc of 3.5 V, short circuit current 12 mA at η, 2.4%. Evaluation of the composition of the Sb2SxSe3−x films through gracing incidence X-ray diffraction is illustrated; and device parameters and solar cell perspectives of these materials are presented.

Aggregation and ordering of helium in thoria

The trapping, aggregation and ordering of helium in thoria (ThO2) was studied by using ion beam irradiation experiments and first principle calculations. Transmission Electron Microscope (TEM) and Gracing Incidence X-Ray Diffraction (GIXRD) studies on thoria irradiated with low energy (100 keV) He+ ions, showed that the lattice has expanded upto 1.07% in isolated nanometric regions where He ions were implanted. In order to distinguish the role of He atoms and ion irradiation induced damage on the lattice expansion, thoria irradiated with 4 MeV Si+ ion was studied, where ion induced damage produced just 0.06% lattice expansion. The observed large lattice expansion in He+ ion irradiated sample is due to the implanted helium atoms. First principle calculations showed that energetics prefer aggregation and ordering of He in the octahedral interstitial sites in thoria lattice, and the ordered aggregation eventually results in lattice expansion of 1.25% which is in agreement with experiments. The experiments and calculations confirm that the observed lattice expansion is due to the ordering of He atoms in the octahedral interstitial sites of thoria.

Effect of Number of Cycles in Potentiodynamic Deposition of p-type Copper Oxide and its Supercapacitor Applications

A well dispersed stable film is synthesized via potentiodynamic deposition technique under ambient conditions and neutral pH. p-type copper oxide is prepared potentiodynamically under a scan rate of 20 mV/s in a potential sphere, which is reaffirmed by virtue of hall measurements. The characterization tools like Gracing Incidence X-ray diffraction, Raman spectroscopy, UV-Visble spectroscopy, photoluminescenece spectroscopy, Scanning Electron Microscope and Hall measurement are used to study the structural, optical, morphological and electrical traits of the thin films. Film thickness plays a pivotal role in supercapacitor application. The amelioration of film thickness for supercapacitor application is attuned by repeating the number of cycles such as 15, 30 and 45. The film formed under 30 number of cycles displays better specific capcitance value with an excellent cyclic stability of 1000 number of cycles and having good charge retention efficiency.

Growth of epitaxially stabilized, non-cubic Gd2O3 on silicon(1 1 1) substrates

We report on the growth of non-cubic gadolinium oxide on a silicon substrate using molecular beam epitaxy. Structural investigations with X-ray diffraction show that the structure of the oxide differs from the expected cubic structure. Possible structures of gadolinium oxide besides the only stable cubic structure include a monoclinic and a hexagonal phase. Both phases are very similar, which increases the difficulty to distinguish between the two structures. Gracing incidence X-ray diffraction results of the grown layer indicate a monoclinic structure while in contradiction to that a phi-scan shows a sixfold symmetry. We explain these results by a monoclinic structure with six rotational domains.

Spatiotemporal Coherent Control of Thermal Excitations in Solids.

X-ray reflectivity measurements of femtosecond laser-induced transient gratings (TG) are applied to demonstrate the spatiotemporal coherent control of thermally induced surface deformations on ultrafast time scales. Using grazing incidence x-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-Å resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in x-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period Λ can be canceled by a second, time-delayed TG excitation shifted by Λ/2. The ultimate speed limits of such an ultrafast x-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments.

Self-Assembly and Near Perfect Macroscopic Alignment of Fluorescent Triangulenium Salt in Spin-Cast Thin Films on PTFE

Highly fluorescent, discotic trioxatriangulenium dyes were aligned by simple spin-casting on substrates with friction transferred PTFE layers. The fluorescent crystalline thin films show near perfect macroscopic alignment on centimeter large areas directly from spin-casting. Gracing Incidence X-ray Diffraction (GIXD) unambiguously allowed the determination of a long-range order unit cell as well as its orientation with respect to the PTFE fibers. Further analysis of the X-ray data, in conjunction with polarized absorption spectroscopy, suggest a lamellar packing model with alternating layers of alkyl chains and ionic dyes oriented parallel to the substrate. This structure results in a highly anisotropic electrostatic potential around the cationic chromophore, causing significant shifts in energy and orientation of the optical transitions. Thus, the optical properties of the material are, to a large extent, controlled by the position of the otherwise inert PF6(-) counterions. The bright fluorescence from the films is also polarized parallel to the PTFE alignment layer. Doping of the thin films with fluorescent energy acceptor traps shows that efficient exciton migration takes place in the thin films. The excellent exciton transfer capabilities, in conjunction with the perfect alignment, might be of interest in future applications in solar energy harvesting or as thin film sensors.

Green to blue polarization compensated c-axis oriented multi-quantum wells by AlGaInN barrier layers

We report on an over 50% reduction in polarization field strength in c-axis oriented InGaN multi-quantum wells (MQW) by applying quaternary AlGaInN barrier layers with better polarization matching to InGaN than GaN barriers. With the reduction in polarization fields, a strong blue-shift in photoluminescence is observed in agreement with theoretical expectation and simulations. By gracing incidence x-ray diffraction measurements, we demonstrate that partial relaxation already occurs for GaN/InGaN MQWs. As a consequence, the requirement of higher In-content layers for green light emission is in conflict with increasing strain leading to lattice relaxation.

Effect of diphenyldiethoxysilane on the self-organized formation of nanocrystalline layered organosilicates in organic–inorganic hybrid films

Hybrid organic–inorganic films containing layered organosilicate nanocrystals have been obtained through self-organization from aqueous precursor sols containing 3-glycidoxypropyltrimethoxysilane. Diethoxydiphenylsilane has been added, in different amounts, to the precursor sol containing 3-glycidoxypropyltrimethoxysilane to prepare hybrid films with the ordered nanostructures. The effect of aging time of the precursor sol has been studied preparing different samples from sols aged up to 8 days; the formation of crystalline layered films has been observed in the samples obtained from sols of higher aging time. The hybrid films have been characterized by gracing incidence X-ray diffraction, Raman and Fourier transform infrared spectroscopy, transmission electron microscopy and UV–Vis spectroscopy. The change of the surface contact angle as a function of sol aging time and composition has been also measured. The capability of the films to be used in devices through lithographic techniques has been tested by writing the films with direct exposition to deep X-ray lithography and soft lithography with micromolds; patterns of different geometries with a thickness up to 100 μm have been obtained.

Influence of reactive oxygen ambience on the structural, morphological and optical properties of pulsed laser ablated potassium lithium niobate thin films

The effect of oxygen ambience on the structure and properties of potassium lithium niobate (K 3Li 2Nb 5O 15: KLN) films prepared on glass substrates by pulsed laser ablation technique (PLD) are studied. The influence of annealing on the properties of vacuum deposited films is also investigated. The Gracing Incidence X-ray Diffraction (GIXRD) data suggests the tetragonal structure for the KLN film whose grain sizes increase on thermal annealing. The Atomic Force Microscopic (AFM) analysis reveals the four-fold symmetric nature of the grains in the films. Self assembly of grains in the form of rings and rods are observed in AFM images of the films deposited in an oxygen ambience of 2 Pa. The films deposited at higher oxygen ambience show a blue shift in optical band gap. The direct current (DC) resistance measurement on the films deposited at non-reactive ambience reveals resistivity in the range of kΩ m.

Characterization of thin Zn–Ni alloy coatings electrodeposited on low carbon steel

The characteristics of initial layer formation in alkaline bath for Zn–Ni (12–15%) alloy electrodeposition on low carbon steel plates are detected in a nanometric thickness range by electron probe microanalysis (EPMA), with both bulk sample and thin film on substrate correction procedure, glow discharge optical emission spectroscopy (GDOES) and gracing incidence X-ray diffraction (GIXRD). The Zn–Ni coatings were elaborated using either intensiostatic or potentiostatic mode. A preferential deposition of Ni, in the initial thin layer, is detected by these analyses; according to EPMA and GDOES measurements, a layer rich in nickel at the interface substrate/deposit is observed (90 wt.% Ni) and approved by GIXRD; the thin layer of Ni formed in the first moments of electrolysis greatly inhibits the Zn deposition. The initial layer depends upon the relative ease of hydrogen and metal discharge and on the different substrate surfaces involved. The electrodeposition of zinc–nickel alloys in the first stage is a normal phenomenon of codeposition, whereby nickel – the more noble metal – is deposited preferentially.

Geometric boundary condition for the chain alignment in lipid monolayers

Langmuir monolayers consisting of phospholipids have been studied intensively in the past using gracing incidence X-ray diffraction (GIXD). Recent investigations focus on monolayers prepared on the surface of complex fluids like hydrogels or -sols (Phys. Rev. Lett. 88 (2002) 25502). These systems allow to modify the properties of the surfactant layer via the tuneable characteristics of the subphase. Using GIXD, the parameters of the lattice formed by the lipid chains are accessible. In addition, the alignment of the scatterer in the unit cell can be extracted from modelling the measured Bragg rods (Transitions in Soft-Condensed Matter, Plenum Press, New York, 1989, pp. 113–138). In this work, we present a boundary condition for the perpendicular wave vector transfer that has to be considered in the calculation of the chain alignment from Bragg rod scans. The theoretical part is illustrated with GIXD measurements of the in-plane structure of lipid monolayers in repulsive electrostatic interaction with charged nano-particles.

Miscibility of DPPC and DPPA in monolayers at the air/water interface

Monolayers of mixtures of 1,2-dipalmitoylphosphatidylcholine (DPPC) as the substrate and 1,2-dipalmitoylphosphatidic acid (DPPA) as the product of the hydrolysis reaction catalyzed by phospholipase D (PLD) were investigated in the presence of Ca 2+. The miscibility behavior and the microstructure of mixed domains have been studied by gracing incidence X-ray diffraction (GIXD), Brewster angle microscopy and film balance measurements. The phase diagram reveals partial miscibility on both sides and a wide miscibility gap, which becomes narrower at high pressure. At low pressure, the segregation of condensed DPPA-rich domains in a fluid-like DPPC matrix was detected already at small DPPA concentrations and their structure was determined. A small amount of DPPC mixed into the segregated DPPA domains induces the transformation from rectangular to an oblique unit cell and increases the tilt angle in the condensed domains. At high pressure, two types of condensed phase domains were found: DPPC-rich and DPPA-rich. A drastic reduction of the tilt angle in the DPPC-rich domains with increasing amount of DPPA was observed. The decrease of the tilt angle must be connected with a change of the head group conformation of DPPC in such mixed domains.

Corrosion Properties of Surface Modified Ti-6Al-7Nb Alloy Under Pulsed Plasma Nitriding and Nitrogen Ion Implantation Conditions

A Ti-6Al-7Nb alloy was surface modified using pulsed plasma nitriding and nitrogen ion implantation in order to study its microstructural changes and corrosion performance. Pulsed plasma nitriding was performed for 30 h at 913 K in a gas mixture of 3:1 N2:H2 under a total pressure of 3 mbar. Nitrogen ion was implanted at 100 keV using a 150 keV accelerator at a dose of 2·5 × 1017 ions cm2. Gracing incidence X-ray diffraction was employed to explore the phases formed after treatments. To characterise the nature of the modified layers produced and to correlate with the corrosion behaviour, SIMS was used. The samples were subjected to electrochemical studies, namely, open circuit potential (OCP)-time measurements and potentiodynamic cyclic polarisation in a simulated body fluid (Ringer's solution). The OCP of the pulsed plasma nitrided and N+ implanted samples were found to shift towards the noble direction (-189 mVSCE and -82 mVSCE, respectively) in comparison with the untreated sample (-338 mVSCE). The passivation current density and area of the repassivation loop were found to decrease for both treatments compared with those in the untreated condition. Nitrogen ion implantation enhanced the passivability and reduced the corrosion kinetics of the alloy with increasing tendency for repassivation. It shows very low passivation current density compared with pulsed plasma nitriding (0·086 and 0·493 μAcm2, respectively). The nature of the modified surfaces and the reason for the variation and improvement in corrosion resistance are discussed.

Nitrogen ion implantation and in vitro corrosion behavior of as-cast Ti–6Al–7Nb alloy

In the present investigation, surface modification of Ti–6Al–7Nb alloy with nitrogen ions is considered as a method to improve its performance with respect to corrosion. Nitrogen ion was implanted on Ti–6Al–7Nb alloy at an energy of 70 and 100 keV using a 150 keV accelerator at different doses between 1×10 16 and 3×10 17 ions/cm 2. Gracing incidence X-ray diffraction was employed on the implanted specimens to understand the phases formed with increasing doses. The implanted samples were subjected to electrochemical study in Ringer's solution in order to determine the optimum dose that can give good corrosion resistance in a simulated body fluid condition. The OCP of the implanted specimens were found to shift in the noble direction in comparison with unimplanted specimen. The passive current density and area of the repassivation loop were found to decrease as the dose values increased. The electrochemical impedance spectroscopic results indicate that the polarization resistance was higher for the dose of 2.5×10 17 ions/cm 2 implanted at both energy of 70 and 100 keV. Nitrogen ion implantation enhanced the passivability and reduces the corrosion kinetics of the alloy surface with increasing tendency for repassivation. Nature of the surface and reason for the variation and improvement in corrosion resistance are discussed in detail.

Effect of Nitrogen Ion Implantation on the Corrosion Resistance of Titanium Modified Type 316L Stainless Steel in Comparison with Argon and Oxygen Ion Implantation

Studies on nitrogen ion implanted (1 x 10 15 , 1 x 10 16 , 1 x 10 17 and 2.5 x 10 17 ions/cm 2 ) titanium modified type 316L stainless steel (SS) showed an increase in the localized corrosion resistance of the material. Gracing Incidence X-ray Diffraction studies showed implanted nitrogen at the interstitial in the specimen implanted at 1 x 10 17 ions/cm 2 which showed the optimum corrosion resistance. Chromium nitride has been found in the dose of 2.5 x 10 17 ions/cm 2 , which showed the inferior corrosion resistance. Argon and oxygen ion implantations were carried out to confirm whether the improvement in the localized corrosion resistance after nitrogen ion implantation was due to chemical effect produced by nitrogen or due to microstructural effect produced by ion implantation. The results showed that nitrogen ion implantation improved more than two fold increase in the localized corrosion resistance with low passive current density. XPS studies of the passive film of implanted specimen (optimum dose) showed the presence of oxynitrides along with oxides which could have contributed to the enhanced corrosion resistance. The argon and oxygen ion implantations did not improve localized corrosion resistance and was found detrimental with increase in doses.