We describe phase formation in thin films of Cr-Ti deposited by sputtering on different substrates and temperatures. Various metastable crystalline and amorphous phases were observed. A metastable fcc phase was observed for the first time. Phase transformations upon laser quenching and in-situ annealing were studied. Spontaneous vitrification of the β-phase was not observed.

X-ray, magnetism and electron loss spectroscopy data were obtained for a series of coherent Fe-Cu face-centred multilayers which suggest that there is a lattice parameter anomaly in the structure. The use of high resolution electron microscopy (HREM) and dark field imaging to measure spacing changes along the layer normal are compared. Experimental dark field images suggest that the Fe has expanded lattice spacings in the growth direction in contradiction to the predictions of a conventional elastic model for a coherent multilayer structure.

In-plane and out-of-plane lattice parameters were measured in a series of coherent Fe-Cu multilayers using non-axial high resolution electron microscopy (HREM). The results indicate that the multilayers are tetragonally distorted with the magnitude of the distortion varying with the thickness of the Fe component. These distortions preclude an understanding of the multilayer structure in terms of conventional elasticity theory. The breakdown of epitaxy for thicker Fe layers was also investigated and it was found that the b.c.c. Fe grew with [110] parallel to [001] of the coherent f.c.c. multilayer.

In the first section of this paper the sputter deposition of thin films of YBa2Cu3O7−x is considered. In the second section low and high temperature heat treatments are discussed in the light of the thermodynamics of the material and in the third the development, fabrication and current-voltage (IV) characteristics of a variety of device structures are described, including the hysterctic characteristics of certain YBa2Cu3O7−x / YBa2Cu3O7−x devices that reveal Josephson supcrcurrcnt tunnelling.

If useful electronic devices are to be fabricated from thin films of the high critical temperature oxide superconductors, such as yttrium barium copper oxide (YBCO), then films must be formed on substrates with dielectric properties which permit device operation at high frequencies, such as sapphire. It is, however, difficult to form high quality YBCO on sapphire because of reaction with the substrate and because epitaxy is not readily achieved. We report the deposition of epitaxial thin films of magnesium oxide, by UHV reactive d.c. magnetron sputtering, on variously orientated substrates of sapphire, and the characterisation of the MgO/sapphire system by x-ray and TEM techniques. Onto such films of MgO on sapphire we have deposited films of YBCO which were strongly textured with the c-axis perpendicular to the plane of the substrate and which were superconducting without the need for a high temperature post deposition anneal.

A few days before the beginning of the 7th European Conference on Applied Superconductivity we learned that Professor Jan Evetts, a pioneer of superconductor research, a brilliant scientist, a wonderful person and a great personal friend, had passed away. We therefore decided to dedicate the 7th European Conference on Applied Superconductivity to the memory of Jan Evetts.

Optical data storage is considered with respect to other data storage methodologies and a context is provided in which research in the area of innovative mass storage technology impinges on the market for optical data products. A case is made for some 'innovative' research to include research topics which will help the optical data storage business in Europe in the next 7-12 years.

Co/Cu multilayers [Co (1.5 nm)/Cu (4 nm)](35) made by magnetron sputtering have been investigated by vibrating-sample magnetometry, electrical resistance measurements and low-angle X-ray diffractometry before and after annealing at 275 degrees C < T < 350 degrees C for selected times. The observed changes in electrical and magnetic properties are small and consistent with a break-up of the Co layers by diffusion of Cu along the grain boundaries within them. The study of the early stages of break-up is facilitated by choosing layer thicknesses greater than would be optimal for GMR. (C) 1999 Elsevier Science B.V. All rights reserved.

Ion assisted deposition techniques offer the control of energetic surface bombardment during film growth. There have been many studies of intrinsic stress in sputtered films, and it has been found that the total energy input at the growing film plays a crucial role in stress development. Using magnetron sputter deposition, with a built-in RF coil to generate a high-density inductively coupled plasma confined close to the substrate, we have studied the stresses of deposited films. It is possible to draw a sufficient ion flux, containing ions of the sputtering gas and the depositing species, to the substrate. Therefore, this process is able to provide controllable energetic ion bombardment, in terms of both flux (by RF power) and energy (by substrate bias), during film growth. Film stress was measured, using a substrate curvature technique, as a function of several deposition parameters including the bombarding ion flux, ion incident energy, ionisation fraction of depositing atoms and operational pressure. By controlling the ion flux and ion incident energy, we are able to control the film stress.

The first simultaneous images of electrochemical activity and surface topography of a substrate in air are reported using a combined scanning force microscope (SFM) and scanning electrochemical microscope (SECM): SF–SECM. In the SF–SECM, the amperometric response of a Pt-coated SFM tip connected as a working electrode is monitored as the probe is scanned over the surface, in contact mode, enabling topographical and electrochemical maps of the surface to be generated simultaneously. This methodology is illustrated through studies of the surface of a track-etched porous membrane (pore diameter 100 nm), hydrated with a solution containing 5×10−3 mol dm−3 potassium hexachloride iridate(III) (electroactive mediator) in excess supporting electrolyte. The optimal conditions for the preparation of the most effective and durable Pt thin film-coated probe, essential for the production of a long-lasting conducting tip, are also determined.

Using X-ray diffraction methods, including pole figure determination, the microstructures of silver buffer layers deposited by magnetron sputtering on to (001) rocksalt are investigated as a function of substrate temperature. A quantitative analysis is reported of the grain orientations, and the transition from (111) orientation polycrystalline films to (001) single-crystal films with increasing substrate temperature is confirmed. In addition, the relative proportion of the two distinct (111) orientation relationships is measured as a function of substrate temperature for the first time. It is shown that the pole-figure technique can be used for quantitative studies of the microtwinning in the (001) silver grains; both the volume fraction (at most 1.5%), and the twin thickness (∼6 nm, from diffraction streaking) can be determined.

Carbon nitride films have been deposited by r.f. and d.c. planar balanced magnetron sputtering under various conditions. The films were analysed by Rutherford back-scattering (RBS), electron energy loss spectroscopy (EELS), and Fourier transform infrared (FTIR) spectroscopy. The deposition rates of the films synthesised by r.f. magnetron sputtering increased with nitrogen content in the sputtering gas. The nitrogen content of the films also increased as the nitrogen content in the sputtering gas was increased to 50 vol.%, and then remained constant. Absorption bands at 1250, 1550 and 2200 cm−1 were detected in FTIR spectra, corresponding to Raman-reactive disordered sp2 carbon, graphite-like sp2 carbon, and nitrile or isocyanate groups, respectively. Additionally, broad absorption around 1000–1200 cm−1, which may be associated with sp3 hybridised carbon, was observed in films deposited with low nitrogen content in the sputtering gas. Sputtering gas total pressure and sputtering power were also varied. The results were interpreted in terms of the collision frequency of the sputtered species with reactive gases in the system. The films deposited with >70% nitrogen in the sputtering gas showed higher friction coefficients and lower wear resistance in sliding friction tests than films grown with lower gas nitrogen content, suggesting that these properties of the films were associated with their structure.

A set of multilayers of Ni/amorphous Ni50Zr50 Of various periodicities was deposited using de planar magnetron sputtering. The diffusion of Ni into the amorphous phase and the strain build-up in the Ni layers were measured in situ from the reduction and shift in Bragg peak intensity and angle respectively. For short periodicities, a lowered interdiffusivity was observed in agreement with other earlier experimental observations and theoretical predictions of stress effects in some amorphous multilayers with a high viscosity. Furthermore, direct evidence of stress formation owing to an unbalanced diffusional flow of the two species in Ni-Zr was obtained. These findings give further support for Stephenson's theory for lowered interdiffusion due to restricted stress relaxation in amorphous alloys.

A UHV deposition system for the production of epitaxial oxide/metal heterostructures on single crystal ceramic substrates is described. The system has two novel features. The first is the use of linked, dedicated UHV sputtering and pulsed laser deposition chambers for the metal and oxide growth respectively, so as to maintain the cleanliness of the metal surface after deposition. The second is the use of a pulsed oxygen source during oxide growth to minimize damage of the metal layer by oxidation during the growth of the oxide layer. This second issue is illustrated by the growth of magnesium oxide/niobium bilayers on sapphire substrates. The magnesium oxide was grown under varying conditions of oxygen supply. A clean niobium film with no magnesium oxide overlayer showed a resistance ratio of 76. If the magnesium oxide was grown under UHV conditions (no extra oxygen supply) then the resistance ratio of the niobium film was reduced to 26. Growth of the magnesium oxide with synchronous 0.6 ms oxygen pulses (total ambient oxygen exposure 121 Pa s) resulted in a niobium resistance ratio of 18. A similar exposure to oxygen pulses alone (no magnesium oxide layer) reduced the niobium resistance ratio to 1.2. Alternatively the magnesium oxide layer could be grown in an argon ambient, with maintenance of the residual resistance ratio at 60 in 20 Pa of argon.

The growth of single crystal/highly textured films of oxides on metals has become of considerable interest recently as a building block to the exploitation of conductors of YBCO based HTS materials. This study describes work in which oxide films are deposited by pulsed laser ablation onto previously deposited, single crystal metal thin films. The metal films are sputter deposited onto single crystal oxide substrates in a linked, but separate, UHV chamber. The samples are then transferred to the laser ablation chamber. Different levels of oxidation are used in the laser ablation process. In its most novel form, the oxide films are grown using a sub-millisecond oxygen pulse synchronised with the ablating laser pulse. In this way the overall oxygen exposure of the metal is minimised and controlled. Other background gases have been introduced to change the environment of the growing oxide films. Epitaxial (002) SrTiO3 has been grown directly on (002) Ni, with a 0.48 degrees rocking curve; this work is being extended to YSZ and CeO2 where there is a greater tendency to grow with a(lll) orientation.

Crystalline-Ni/amorphous-Ni50Zr50 and crystalline-Co/amorphous-Co50Zr50 multilayers were produced by de planar magnetron sputtering. Magnetic hysteresis loops were measured using a vibrating sample magnetometer. Multilayers were characterised in the as-deposited state, and after successive isothermal anneals. For the c-Ni/a-NiZr multilayers, the change in the hysteresis loops on annealing is consistent with a reversal in anisotropy brought about by a diffusion-induced tensile stress in the magnetic Ni layers. The c-Co/a-CoZr films show no such changes in hysteresis on annealing. The divergence in the behaviour of the two different types of film is attributed to the difference in the magnetic properties of Ni and Co.

The aim of this work is the fabrication of heterostructures of epitaxial oxides and metals for device applications. The epitaxial metals are deposited on R-plane sapphire substrates by de magnetron sputtering in a linked UHV system. The oxide layer is then grown on top of this metal layer in a linked UHV pulsed laser deposition (PLD) system using a pulsed oxygen jet to provide oxidation of the ablation products while minimising oxidation of the metal layer. Isolating the oxide deposition from the metal deposition avoids contamination of the sputtering process which enables, very high quality, single crystal metal films to be produced. In this preliminary study the length of the oxygen pulse was varied during the initial growth of MgO on Nb to investigate when the epitaxial oxide nucleation became significantly degraded. The full width half maximum (FWHM) of the X-ray diffraction rocking curve was used as a gauge of the quality of the epitaxy (Nb: 0.33 degrees--0.92 degrees; MgO: 0.81 degrees--3.43 degrees). The results suggest that oxidation of the surface of the metal does indeed affect the epitaxy of the MgO overlayer with an oxygen pulse length greater than 3 ms. The purity of the metal base layers was examined by residual resistance ratio (10 K to 293 K) and found to be in the range of 75 for a clean Nb film to 1.1 for a heavily oxidised Nb film. (C) 1997 Elsevier Science Ltd. All rights reserved.

We have investigated the capacitance of grain boundary Josephson junctions deposited on symmetric 24/spl deg/ misoriented SrTiO/sub 3/ bicrystal substrates using hysteresis and Fiske resonances in their current voltage characteristics. Our measurements show that the total junction capacitance is proportional to the junction area. The capacitance per unit area is (140/spl plusmn/30) fF /spl mu/m/sup -2/ and this implies that the main effect of the large relative permittivity of the substrate is to scale-up the grain boundary capacitance by a factor of around 10. We also find that in the planar geometry of bicrystal grain boundary junctions the velocity of light in the junction depends upon film thickness.

A study of the reactive DC magnetron deposition of TiNx films has been performed, from nitrogen/argon mixtures containing from 5 to 50% nitrogen and with substrate temperatures from 150 to 700 degrees C. The microhardness, chemical composition, crystallographic texture and deposition rate of the films were studied in detail. At a substrate temperature of 600 degrees C, deposition rate increased as the gas nitrogen content decreased. From 20 to 50% nitrogen, the nitrogen content of the films increased as the nitrogen content in the gas decreased. The film microhardness increased with increasing nitrogen/argon ratio. As substrate temperature was decreased, the nitrogen content in the films increased and microhardness decreased. Films grown below ca. 500 degrees C showed (Ill)orientation. For higher temperatures and from 50% nitrogen atmospheres, the dominant orientation changed to (200).