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Exchange-bias has been reported in bulk nanocrystalline Fe2MnAl, but individual thin films of this Heusler alloy have never been studied so far. Here we study the structural and magnetic properties of nanocrystalline thin films of Fe2−xMn1+xAl (x = −0.25, 0 and 0.25) obtained by sputtering and ex situ post-deposition annealing. We find that Fe2MnAl films display exchange-bias, and that varying Mn concentration determines the magnitude of the effect, which can be either enhanced (in Fe1.75Mn1.25Al) or suppressed (in Fe2.25Mn0.75Al). X-ray diffraction shows that our films present a mixed L21–B2 Heusler structure where increasing Mn concentration favors the partial transformation of the L21 phase into the B2 phase. Scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX) reveal that this composition-driven L21 → B2 transformation is accompanied by phase segregation at the nanoscale. As a result, the Fe2−xMn1+xAl films that show exchange-bias (x = 0, 0.25) are heterogeneous, with nanograins of an Fe-rich phase embedded in a Mn-rich matrix (a non-negative matrix factorisation algorithm was used to give an indication of the phase composition from EDX data). Our comparative analysis of XRD, magnetometry and X-ray magnetic circular dichroism (XMCD), shows that the Fe-rich nanograins and Mn-rich matrix are composed of a ferromagnetic L21 phase and an antiferromagnetic B2 phase, respectively, thus revealing that exchange-coupling between these two phases is the cause of the exchange-bias effect. Our work should inspire the development of single-layer, environmentally friendly spin valve devices based on nanocomposite Heusler films.

Exchange-bias has been reported in bulk nanocrystalline Fe

The dependency of the surface-to-volume coordination number upon particle size has been obtained by an analytical function based upon our previous work, and a model for melting temperature as a function of size is presented. This expression for the melting temperature is a nonlinear relation in terms of the reciprocal of size. Also, the geometrical characteristics of nanoclusters have been applied to our general equation for the melting temperature of nanoparticles. It was found that the results of considering the geometrical characteristics of nanoclusters are in good agreement with the melting temperature achieved by the derived analytical function. Finally, this model has been compared with other theoretical models as well as the available experimental data. The predictions are consistent with the experimental data.

Nanocomposite thin films of titanium silicon nitride were deposited by sputtering on R-plane sapphire substrates. The effects of silicon addition and negative substrate bias on the texture development of the films were studied systematically by varying the bias voltage in the range −20 to −200 V. The accompanying changes in the microstructure and growth morphology of the phases in these films were investigated in detail using X-ray diffraction and a atomic force microscopy. In addition, the effect of texture on the mechanical properties of the films was also investigated using nanoindentation technique. Pure TiN films deposited without Si exhibit a strong (1 1 1) preferred orientation, while with addition of Si, the orientation of the films changes from (1 1 1) to (2 0 0). Meanwhile the surface morphology of these films changed from a pronounced columnar microstructure to a dense, fine-grained structure. The effect of negative substrate bias voltage applied during deposition also resulted in a similar change of film orientation and microstructure and leads to the increase in hardness of the films from 21 to 40 GPa, respectively.

Ferroelectric Bi4–x Sm x Ti3O12 (BSmT) thin films have been fabricated on Pt/TiO x /SiO2/Si substrates by pulsed laser deposition (PLD) and their ferroelectric properties have been characterised. The remanent polarisation (2P r ) was 17.5 μ C/cm2, 41.8 μ C/cm2, 9.3 μ C/cm2, for x = 0.55, 0.70, and 1.00, respectively, at an applied maximum field of 450 kV/cm. The polarisation of the BSmT (x = 0.70) film decreased to 86% of the initial value after 5.0× 108 switching cycles.

A strain gradient has been observed along the growth direction of 5 μm thick diamond films, grown on silicon wafers. On detachment, films were found to adopt curvature such that the free surfaces became concave which indicates residual stresses which are compressive near the interface and tensile near the free surface. Raman peak positions were found to shift upward near the interface and downward near the growth surface. Raman spectra from the interface showed higher level of sp2 hybridized carbon. The quality of the diamond was found to improve as the film thickness increased. Luminescence spectra were also examined to study the variation in defect density across the film thickness and its possible contribution to the observed strain gradient.

Thin films of TiN have been deposited by reactive magnetron sputter deposition in varying partial pressures of nitrogen. Reflectivity measurements have been carried out between 1.5 and 3.5 eV and a correlation made between the film properties and optical data. Resistivity measurements carried out at room temperature are shown to exhibit the same trends as those obtained from reflectivity experiments. X-ray absorption fine structure measurements, in both electron-yield and fluorescence-yield modes, have shown the films to be identical and stoichiometric to within ±5 at.%. The use of reflectivity spectra to form the basis of a characterization tool for physical vapour deposited thin films is discussed.

Surface enhanced Raman spectroscopy was performed by depositing Ag particles by dc sputtering on thin diamond films prepared by hot filament chemical vapor deposition. Enhancement of Raman signal by a factor up to 100 could be obtained by controlling the Ag particle size. Raman spectra from different locations through the thickness of diamond films indicate a variation in the carbon structures. Phonon density of states of diamond and graphite are considered along with previously reported observations, to analyze the additional bands which appear in the SERS scattering as a consequence of the presence of the Ag particles.

The ionized physical vapor deposition technique uses a built-in rf coil to generate an inductively coupled plasma (ICP) between the target and substrate holder. For deposition of metallic species, a portion of the depositing atoms is ionized upon passing through the ICP. Since the input energy of the ICP is decoupled from the target, this technique also provides controllable ion bombardment during film growth, in terms of bombarding ion flux and ion energy. An ionized physical vapor deposition system has been studied and fully characterized. The ICP was characterized using a single passive probe method, and the plasma parameters, including electron temperature, plasma potential, and plasma ion density, have been measured. The ionization fraction of the depositing metal flux as a function of deposition parameters has been measured using the single passive probe method and a self-developed parallel-plates method. A simplified one-dimensional model was developed and compared favorably with the measured ioniz...

Spatially resolved optical emission spectroscopy has been used to investigate the sputtering and ionization of titanium in a DC planar magnetron using argon as a sputtering gas. Maps of argon and titanium atomic and ionic emission have been obtained. Characteristic emission patterns have been identified and explained by the sputtering of atoms from the magnetron target and their subsequent ionization in the dense plasma at the magnetron target. The inverse Abel transformation was used to reconstruct plasma emission profiles, revealing that the non-uniform erosion profile at the magnetron target leads to a non-uniformity in plasma properties some distance into the discharge. An enhanced metal ionic content has been found in the plasma on the axis of symmetry of the discharge, and this has been explained by an enhanced lateral diffusion of metal ions arising from the change in momentum of sputtered metal during collisional ionization by metastable argon atoms.

Emission spectra in the visible and near ultraviolet have been recorded for the magnetron sputtering of titanium by argon at pressures between 0.5 and 100 Pa. Intense emission lines from both atomic and ionic material were detected, and comparison of line intensities yielded an ionization fraction of over 10% and an electron temperature of the order of 1 eV for the sputtered material. The ionization fraction decreased with increasing magnetron power, and an optimal operating pressure was found for maximum ion content of the sputtered flux. Scaling laws of emission line intensity with magnetron power indicated the incomplete thermalization of sputtered metal with the sputtering plasma, and spatially resolved measurements of ionization profiles were used to investigate the transport and collisional ionization of sputtered material. Penning ionization of sputtered titanium by metastable argon was found to be the dominant ionization process, and the effect of diffusion of metastable argon was noted. Control of ion content in sputtered fluxes is of interest for the deposition of thin films and for metallization of semiconductors.

Tungsten trioxide films were deposited on (100) SrTiO3 and R-plane (10 2) cut sapphire substrates by dc magnetron sputtering, using a tungsten target in an Ar/O2 sputtering gas mixture at substrate temperatures ranging from 500 to 850 °C. Deposited films were characterized by x-ray diffraction using -2 scans and pole figure analysis. X-ray results showed that films deposited on both types of substrate were epitaxial. The equilibrium phase was monoclinic -WO3 , confirmed by Raman spectroscopy. Films on both substrates were (001) oriented. This preferred orientation improved as the deposition temperature was reduced. The in-plane orientation relationship of the films with the substrate was obtained from the pole figures.

Silver films have been deposited under controlled ion bombardment by ionized magnetron sputter deposition (IMSD). The technique uses a built-in rf coil to generate an inductively coupled plasma confined close to the substrate. This enables precise control of both the bombarding ion flux (by rf power) and the energy (by substrate bias). By varying the flux and energy of bombarding ions, the film’s structure and properties can be easily modified. Crystallography, grain size, and film texture have been characterized using the x-ray diffraction method, and film stress was measured by a substrate curvature technique. A focused ion beam was used to section the deposited films and to observe the surface morphology and cross-sectional structure. The electrical resistivity ratio (room to liquid nitrogen temperature: R298 K/R77 K) was used to investigate the influence of the film structure on the conductivity. The persistence of bombardment induced film property variation with thickness was studied in terms of the texture variation in bilayers consisting of IMSD and magnetron sputtering deposited films. It is found that the microstructure of deposited films depends predominantly on the ion bombardment during the initial stages of film growth. Using the IMSD technique, the structure and related properties of silver films have been modified by depositing films under precisely controlled ion bombardment.

Transport critical current measurements have been performed on 5 degrees [001]-tilt thin film YBa(2)Cu(3)O(7-delta) single grain boundaries with the magnetic field rotated in the plane of the film, phi. The variation of the critical current has been determined as a function of the angle between the magnetic field and the grain boundary plane. In applied fields above 1 T the critical current j(c) is found to be strongly suppressed only when the magnetic field is within an angle phi(k) of the grain boundary. Outside this angular range the behavior of the artificial grain boundary is dominated by the critical current of the grains. We show that the phi dependence of j(c) in the suppressed region is well described by a flux cutting model.

A Materials Science overview of the deposition of ceramic superconductors is presented. Whilst in the last four years the major effort has gone into the deposition of YBa2Cu3O7-∂ (YBCO), the bismuth and the thallium compounds will also be considered. The two major techniques of laser ablation and “off axis” sputtering will be discussed as well as evaporation, molecular beam epitaxy (MBE) and metallo-organic chemical vapour deposition (MOCVD). Emphasis will be placed on the in-situ deposition technique for YBCO though some consideration will be given to the “post heat treatment” methods being used for the bismuth and thallium compounds. One of the fundamental issues to be addressed will be the relationship between the deposition conditions and the properties of the films produced. The key issues of nucleation will be discussed, aiming at an understanding of the outstanding problems of preparing smooth uniform films.

Nanoindentation allows the hardness of thin coatings and synthetic multilayer structures to be measured, since indentation depths can be as little as a few 10s of nm. In combination with the cross-sectional transmission electron microscopy (TEM) analysis described here it is possible to observe the deformation structure under an indent, and potentially to understand deformation mechanisms on a nm scale in a wide variety of materials. Synthetic multilayers are a particularly interesting system to investigate. Variations in hardness with the multilayer compositional repeat distance (A) have been reported for several systems. The highest hardnesses, which are in excess of what a simple “rule of mixtures” would predict, occur in nitride multilayers at A ∼5nm. Here we present some preliminary results showing the deformation structure in both a monolithic NbN film and a TiN/NbN multilayer in which both components have the rQck salt structure with lattice parameters 0.424nm (TiN) and 0.439nm (NbN).

Thin films of Ti–Si–N have been deposited by ionized magnetron sputter deposition using separate Ti and Si targets in an Ar/N2 gas mixture. A built-in rf coil generated an inductively coupled plasma close to the substrate. With this setup, the ion flux and energy can be controlled by adjusting the rf power to the coil and the dc substrate bias. Deposition was carried out under various conditions to investigate the effects of different operational parameters on film structure and mechanical properties. Crystallography, grain size, and film texture have been characterized by x-ray diffraction, showing that the addition of Si to TiN films transforms the (111)-oriented structure to a preferred (200)-oriented structure. The nanocrystallite domain size of the TiN, calculated from peak broadening, was found to be less than 10 nm. No signals from crystalline Si3N4 or other phases of titanium silicide were observed. The hardness of the films, measured using nanoindentation, increased to as much as twice that of pure TiN films.Thin films of Ti–Si–N have been deposited by ionized magnetron sputter deposition using separate Ti and Si targets in an Ar/N2 gas mixture. A built-in rf coil generated an inductively coupled plasma close to the substrate. With this setup, the ion flux and energy can be controlled by adjusting the rf power to the coil and the dc substrate bias. Deposition was carried out under various conditions to investigate the effects of different operational parameters on film structure and mechanical properties. Crystallography, grain size, and film texture have been characterized by x-ray diffraction, showing that the addition of Si to TiN films transforms the (111)-oriented structure to a preferred (200)-oriented structure. The nanocrystallite domain size of the TiN, calculated from peak broadening, was found to be less than 10 nm. No signals from crystalline Si3N4 or other phases of titanium silicide were observed. The hardness of the films, measured using nanoindentation, increased to as much as twice that of pu...

Details are presented of the design of a small DC planar magnetron source and its use in a research-scale UHV getter sputter deposition system. The system has been used for depositing a range of refractory materials as well as some metal multilayer structures (single crystal, polycrystalline and amorphous). For some of these structures a relatively high sputtering pressure is required and a study has been made of the deposition rate as a function of pressure for a range of different elements. This illustrates the effect of the momentum and energy transfer of the sputtered atoms as they travel from the target to the substrate.