Glancing Angle X-ray Diffraction Measurements Research Articles

Bismuth Phase Dependent Growth of Superconducting NiBi3 Nanorods

We report a study on the growth of NiBi3 nanowires and nanorods during the preparation of superconducting NiBi3 films by co-evaporation of Ni and Bi. We find that NiBi3 films grown via co-evaporation of Ni and Bi metals achieve higher transition temperatures (4.4 K) compared even to the single crystal NiBi3. However, in certain parameter space, the film surfaces were spattered with nanoscale features, such as nanowires and nanorods. Ambient temperature deposition resulted in poly-crystalline NiBi3 nanorods which were controllable with the evaporation rate of Bi. Deposition at elevated temperatures promoted the emergence of long single crystalline NiBi3 nanorods. High resolution transmission electron microscopy measurements confirmed the crystalline behaviour of the nanorods. We believe that NiBi3 nanowires form in a process analogous to the well known vapor-liquid-solid process, as we observe an amorphous Bi cap on the nanorods. From glancing angle X-ray diffraction measurements we identify that the presence of trigonal Bi with hexagonal primitive cell in the film promotes the nucleation of nanorods. Electrical transport on a single NiBi3 nanowire shows a superconducting transition of 4.3 K.

Fractal characterizations of MeV ion treated CaF2 thin films.

We present the morphological evolution and fractal characterizations of CaF2 thin-film surfaces modified by bombardment with 100 MeV Au+8 ions at various fluences. Atomic force microscopy (AFM) combined with line profile and two-dimensional power spectral density (2D-PSD) analysis was utilized to investigate the evolution of surface morphology as a function of fluence. The AFM images were utilized to investigate the relationship between fractal dimension, roughness exponent, lateral correlation length, and ion fluence. The surface erosion owing to sputtering was depicted using Rutherford backscattering spectrometry. The structural characteristics' dependency on fluence was explored with the help of glancing angle x-ray diffraction measurements on virgin and irradiated samples. Tensile stress calculated using a peak shift in the glancing angle x-ray diffractogram showed an increase in tensile stress with fluence that caused the surface to crack after the fracture strength of the surface was crossed. 2D-PSD analysis signified the role of sputtering over surface diffusion for the observed surface modifications. Fractal dimensions first increased and then decreased with ion fluence. The lateral correlation length decreased, while the roughness exponent increased with fluence after the threshold value.

Defects controlling electrical and optical properties of electrodeposited Bi doped Cu2O

Doping leading to low electrical resistivity in electrodeposited thin films of Cu2O is a straightforward requirement for the construction of efficient electronic and energy devices. Here, Bi (7 at. %) doped Cu2O layers were deposited electrochemically onto Si(100) single-crystal substrates from aqueous solutions containing bismuth nitrate and cupric sulfate. X-ray photoelectron spectroscopy shows that Bi ions in a Cu2O lattice have an oxidation valence of 3+ and glancing angle X-ray diffraction measurements indicated no presence of secondary phases. The reduction in the electrical resistivity from undoped to Bi-doped Cu2O is of 4 and 2 orders of magnitude for electrical measurements at 230 and 300 K, respectively. From variations in the lattice parameter and the refractive index, the electrical resistivity decrease is addressed to an increase in the density of Cu vacancies. Density functional theory (DFT) calculations supported the experimental findings. The DFT results showed that in a 6% Bi doped Cu2O cell, the formation of Cu vacancies is more favorable than in an undoped Cu2O one. Moreover, from DFT data was observed that there is an increase (decrease) of the Cu2O band gap (activation energy) for 6% Bi doping, which is consistent with the experimental results.

Progressive magnetic softening of ferromagnetic layers in multilayer ferromagnet-nonmagnet systems and the role of granularity

We report a study of the structural and magnetic behavior of the topmost magnetic layer in a ferromagnet-nonmagnet (Co-Au) multilayer system. Glancing angle X-ray diffraction measurements performed on a series of multilayers showed a gradual decrease in the grain size of the topmost magnetic layer with the increasing number of bilayers. Concurrently, the magnetic hardness and magneto-crystalline anisotropy of the top Co layer were found to decrease, as observed by magneto-optical Kerr effect measurements. This magnetic softening has been discussed in the light of Herzer's random anisotropy model. Micromagnetic simulations of the multilayer system also corroborated these observations.

Properties of Nitrogen-Doped Zinc Telluride Films for Back Contact to Cadmium Telluride Photovoltaics

Zinc telluride (ZnTe) films have been deposited onto uncoated glass superstrates by reactive radiofrequency (RF) sputtering with different amounts of nitrogen introduced into the process gas, and the structural and electronic transport properties of the resulting nitrogen-doped ZnTe (ZnTe:N) films characterized. Based on transmission and x-ray diffraction measurements, it was observed that the crystalline quality of the ZnTe:N films decreased with increasing nitrogen in the deposition process. The bulk carrier concentration of the ZnTe:N films determined from Hall-effect measurements showed a slight decrease at 4% nitrogen flow rate. The effect of ZnTe:N films as back contact to cadmium telluride (CdTe) solar cells was also investigated. ZnTe:N films were deposited before or after CdCl2 passivation on CdTe/CdS samples. Small-area devices were characterized for their electronic properties. Glancing-angle x-ray diffraction measurements and energy-dispersive spectroscopy analysis confirmed substantial loss of zinc from the samples where CdCl2 passivation was carried out after ZnTe:N film deposition.

Fabrication of hematite nanowire arrays on pure iron via anodization process for superhydrophilic surfaces

In this work, hematite nanowire arrays (HNA) were fabricated on pure iron foil by using anodization process in fluoric electrolyte to produce superhydrophilic surfaces. The in situ growth of HNA on iron substrates was ascertained by scanning electron microscopy images, X-ray photoelectron spectroscopy and glancing angle X-ray diffraction measurements. The resultant HNA-bearing iron surfaces showed superhydrophilic property with a contact angle of 7 ± 2°, and its super-hydrophilicity remained longer than three days in air.

Fabrication and characteristics of ta-C biomaterial coatings on Ti–6Al–4V using metal plasma immersion ion implantation and deposition

We have formed amorphous diamond (ta-C) coatings on Ti–6Al–4V substrates using a metal plasma immersion ion implantation and deposition (MEPIIID) technique, and characterized the mechanical properties and biological compatibility of the coating material. The hemocompatibility of the coating compared favorably with that of low temperature isotropic (LTI) carbon, with kinetic clotting time and hemolysis rate approximately the same as for LTI carbon, and platelet consumption about twice that of the latter. The mechanical properties were good, with a microhardness greater than that of the uncoated metal substrates, and high adhesion of >0.75 GPa (interface shear stress) as estimated from a thermal quench method. Glancing-angle X-ray diffraction measurements indicated the presence of a TiC transition layer, suggesting the formation of a Ti/TiC/ta-C multilayer structure, leading in turn to good film–substrate adhesion. We conclude that this kind of amorphous diamond coating could provide benefit as a biocompatible hard coating for Ti–6Al–4V substrate material.

Low Resistance and Thermally Stable Pt/Ru Ohmic Contacts to p-Type GaN

High-quality Pt (20 nm)/Ru (50 nm) Ohmic contacts to surface-treated p-GaN with lowest resistance and thermal stability are reported. The electrical properties and interfacial reactions of the contacts to GaN were investigated using current–voltage, Auger electron spectroscopy, and glancing angle X-ray diffraction measurements. It is shown that the as-deposited contact produces a specific contact resistance of 7.8(±2.2) × 10—4 Ωcm2, while the contact annealed at 600 °C for 2 min yields a resistance of 2.2(±2.0) × 10—6 Ωcm2. The latter is believed to be the lowest value reported so far for Ohmic contacts to p-GaN. It is further shown that the contacts exhibit excellent thermal stability during annealing at 600 °C.

High-energy metal ion implantation into titanium dioxide films

Titanium dioxide (TiO 2) films prepared by a sol-gel method were irradiated with 0.5 MeV V, Ti and 1.8 MeV Au ions and subsequently annealed at approximately 480°C. After the implantation and thermal annealing, the microstructure and the optical properties of the TiO 2 films were studied by Rutherford backscattering spectrometry (RBS), optical absorption and glancing angle X-ray diffraction measurements. It was found that the distribution of the implanted metal was slightly changed after annealing. The absorption edge of the films also slightly shifted toward the longer wavelength side. The films were composed of anatase and rutile phases. The anatase phase was reduced by ion implantation.

Scratch-resistant transparent boron nitride films

Transparent boron nitride (BN) coatings were deposited on glass and Si substrates in a conventional capacitively coupled RF PACVD system starting from diborane (diluted in helium) and nitrogen. By varying the plasma conditions (bias voltage, ion current density), coatings were prepared with hardness values ranging from 2 to 12 GPa (measured with a nano-indenter). Infrared absorption measurements indicated that the BN was of the hexagonal type. A combination of glancing-angle X-ray diffraction measurements and simulations shows that the coatings consist of hexagonal-type BN crystallites with different degrees of disorder (nanocrystalline or turbostratic material). High-resolution transmission electron microscopy analysis revealed the presence of an amorphous interface layer and on top of this interface layer a well-developed fringe pattern characteristic for the basal planes in h-BN. Depending on the plasma process conditions, these fringe patterns showed different degrees of disorder as well as different orientational relationships with respect to the substrate surface. These observations were correlated with the mechanical properties of the films.

Ion-beam-assisted deposition of aluminium and aluminium alloy coatings for corrosion protection

Ion-beam-assisted deposition (IBAD) was used for depositing pure aluminium coatings on low carbon steel in order to study the corrosion properties as a function of the energy of the incident argon ions, the ion-to-atom arrival ratio and the angle of ion incidence. With theoretical considerations about the localized corrosion behaviour of substrate-coating systems it is possible to evaluate the porosity, the relative number of coating defects and their mean diameter. Their dependence on the process parameters gives an insight into the initial stages of film growth and shows that the energy deposition in the near-surface region is the most important factor for modifying coating defects and therefore the corrosion properties of the steel-aluminium system. The modification potential of each parameter of IBAD is studied in comparison to pure vapour deposition for the corrosion in acetate buffer. In chloride-containing aqueous solutions the depassivation behaviour of aluminium can be improved by use of alloying elements. Aluminium and magnesium were deposited on inert glass substrates; the magnesium concentration and the bombarding energy were varied. The resulting alloys have equilibrium potentials less noble than pure aluminium and increased passive regions. The passive region decreases with increasing magnesium concentration. From glancing-angle X-ray diffraction measurements it can be seen that structural changes influenced by the ion beam go parallel with changes in the localized corrosion behaviour.

Irradiation effect of rare-gas ions in type 304 austenitic stainless steel

Ar, Kr and Xe rare-gas ions were irradiated in foil specimens of type 304 stainless steel. An irradiation effect in the surface region of the foil specimens has been investigated by means of glancing angle X-ray diffraction (GXRD), Rutherford backscattering (RBS) and particle-induced X-ray emission (PIXE) in order to observe the retained rare-gas atoms and elucidate their correlation with the ion-induced martensitic phase transformation of γ phase → α phase. It has been seen that the amounts of Ar, Kr and Xe retained in stainless steel as estimated from PIXE spectra were affected by the sputtering under ion irradiation. It has been shown by GXRD measurements that the retained rare-gas atoms agglomerated and formed a highly-pressurized solid phase inclusion. It is clear from GXRD measurements that the amount of the phase transformation at saturation increased linearly with increasing ion range of the implanted rare-gas atoms irrespective of the ion species. We speculate from this linearity that the depth distribution of the ion-induced martensitic phase may overlap with that of the rare-gas inclusion in stainless steel, and the formation of the rare-gas inclusion has stress-induced the phase transformation of γ → α. However, before saturation of the ion-induced phase transformation, the degree of the phase transformation in stainless steel as estimated from the amount of retained rare-gas atoms clearly differed for the different ion species.