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The purpose of this study was to identify and correlate the microstructural and luminescence properties of europium-doped Y 2 O 3 (Y 1-x Eu x ) 2 O 3 thin films deposited by metallorganic chemical vapor deposition (MOCVD), as a function of deposition time and temperature. The influence of deposition parameters on the crystallite size and microstructural morphology were examined, as well as the influence of these parameters on the photoluminescence emission spectra. (Y 1-x -Eu x ) 2 O 3 thin films were deposited onto (111) silicon and (001) sapphire substrates by MOCVD. The films were grown by reacting yttrium and europium tris(2,2,6,6-tetramethyl-3,5-heptanedionate) precursors with an oxygen atmosphere at low pressures (5 torr (1.7 x 10 3 Pa)) and low substrate temperatures (500°-700°C). The films deposited at 500°C were smooth and composed of nanocrystalline regions of cubic Y 2 O 3 , grown in a textured [100] or [110] orientation to the substrate surface. Films deposited at 600°C developed, with increasing deposition time, from a flat, nanocrystalline morphology into a platelike growth morphology with [111] orientation. Monoclinic (Y 1-x -Eu x ) 2 O 3 was observed in the photoluminescence emission spectra for all deposition temperatures. The increase in photoluminescence emission intensity with increasing postdeposition annealing temperature was attributed to the surface/grain boundary area-reduction effect.

As part of a larger study to investigate atomic-diffusion behavior in both elemental boron and refractory transition-metal borides, neutron reflectometry was used to examine the temperature-induced self-diffusion of isotopically enriched thin films of amorphous $^{11}\mathrm{B}$ on $^{10}\mathrm{B}$ deposited by electron-beam evaporation. The reflectometry studies were performed and model boron density profiles for samples annealed at various times and temperatures of 360 and 400 \ifmmode^\circ\else\textdegree\fi{}C were fit to the reflectivity data. Although the $^{10}\mathrm{/}^{11}$B interface did not move relative to the air/boron interface upon annealing, the expected standard Fickian diffusion for the annealed samples was not observed. A pinned Fickian diffusion model, which imposes the boundary conditions of a fixed composition of $^{10}\mathrm{B}$ to $^{11}\mathrm{B}$ at the interface, fit the reflectivity data accurately and consistently. A typical equilibrium diffusion constant was determined to be \ensuremath{\sim}${10}^{\mathrm{\ensuremath{-}}17}$ ${\mathrm{cm}}^{2}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, measured at an annealing temperature of 360 \ifmmode^\circ\else\textdegree\fi{}C. The measured diffusion constants are inconsistent with the high melting temperature of elemental boron, but are consistent with measured boron diffusion constants in other amorphous thin films. The presence of clusters in the boron film is proposed to explain the observed results.

Carbon films with up to 32 at. % of nitrogen have been prepared with ion beam assisted magnetron, using a N2+/N+ beam at energies between 50 and 300 eV. The composition and density of the films vary strongly with the deposition parameters. EELS, SXS, XPS, and IR studies show that these a-C: N films are mostly graphitic and have up to 20% sp3 bonding. Nitrogen is mostly combined with carbon in nitrile (C ≡ N) and imine (C=N) groups. It is shown by RBS and NDP that density goes through a maximum as the average damage energy per incoming ion increases. Positron annihilation spectroscopy shows that the void concentration in the films goes through a minimum with average damage energy. These results are consistent with a densification induced by the collisions at low average damage energy values and induced graphitization at higher damage energy values. These results are similar to what is observed for Ar ion assisted deposition of a-C films. The mechanical properties of these films have been studied with a nanoindenter, and it was found that the hardness and Young's modulus go through a maximum as the average damage energy is increased. The maximum of mechanical properties corresponds to the minimum in the void concentration in the film. Tribological studies of the a-C: N show that the friction coefficient obtained against diamond under dynamic loading decreases strongly as the nitrogen composition increases, this effect being more pronounced at low loads.

Epitaxial TiN/V0.3Nb0.7N superlattices with a 1.7% lattice mismatch between the layers were grown by reactive magnetron sputtering on MgO(001) substrates. Superlattice structure, crystalline perfection, composition modulation amplitudes, and coherency strains were studied using transmission electron microscopy and x-ray diffraction. Hardness H and elastic modulus were measured by nanoindentation. H increased rapidly with increasing Λ, peaking at H values ≍75% greater than rule-of-mixtures values at Λ ≍ 6 nm, before decreasing slightly with further increases in Λ. A comparison with previously studied lattice-matched TiN/V0.6Nb0.4N superlattices, which had nearly identical composition modulation amplitudes, showed a similar H variation, but a smaller H enhancement of ≍50%. The results suggest that coherency strains, which were larger for the mismatched TiN/V0.3Nb0.7N superlattices, were responsible for the larger hardness enhancement. The results are discussed in terms of coherency strain theories developed for spinodally decomposed materials. Nanoindenter elastic modulus results showed no significant anomalies.

A hybrid process, aerosol-assisted chemical vapor deposotion (AACVD), is described for reproducible preparation of superconducting thin films of YBa 2 Cu 3 O 7−χ . The process consists of atomizing a toluene solution of the Y, Ba, and Cu tetramethylheptanedionato complexes using an aerosol generator. The aerosol is transported into a CVD reactor where solvent and precursor evaporation and deposition occur at atmospheric pressure on heated substrates. The process provides stable evaporation rates for all three precursors, yielding constant film stoichiometry throughout the deposition period and from film to film. Superconducting films may be deposited in-situ at substrate heater temperatures above 825°C, or may be formed at lower temperatures by deposition followed by post-deposition annealing at higher temperatures. The microstructure and quality of films are highly dependent on the conditions employed in deposition and in the case of films deposited below 825°C, the post-deposition annealing conditions. Superconducting films prepared by the AACVD/post-annealing process have a metallic normal state resistivity signature with a zero resistance temperature typically above 88K, and are highly c -axis oriented. Transport critical current densities measured at 75 K on polycrystalline films prepared by the AACVD process are 220 000 A/cm 2 and 84 000 A/cm 2 at self-field and 0.1 T, respectively.

Films of Ba-Ca-Cu-O have been RF-magnetron-sputtered onto Consil 995 substrates. A postdeposition anneal in an overpressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, a novel approach to the electrical characterization of these films on a conductive substrate, is discussed and compared with SEM (scanning electron microscope), XRD (X-ray diffraction) and RBS (Rutherford backscattering) measurements as a function of differing annealing protocols. The improvement in the superconducting responses as a function of annealing procedures correlates well with the improved morphology observed in the SEM photographs. Also, the XRD data show increased c-axis material with the C annealing protocol.

We have investigated the fabrication of thin‐film superconductors by Cu‐ion implantation into initially Cu‐deficient Y(BaF2)Cu thin films. The precursor films were co‐evaporated on SrTiO3 substrates, and subsequently implanted to various doses with 400 keV 63Cu2+. Implantations were performed at both LN2 temperature, and at 380 °C. The films were post‐annealed in oxygen, and characterized as a function of dose by four‐point probe analysis, x‐ray diffraction, ion‐beam backscattering and channeling, and scanning electron microscopy. It was found that a significant improvement in film quality could be achieved by heating the films to 380 °C during the implantation. The best films made became fully superconducting at 60–70 K, and exhibited good metallic R vs T behavior in the normal state.

A multi-step process is used to fabricate Tl2Ba2Ca1Cu2O8 films on (100) LaA103 substrates. Submicron thick precursor films of Ba-Ca-Cu-O are rf magnetron sputter deposited from a single target. Film stoichiometry is measured by ion beam backscattering spectroscopy. Deficiencies of the alkaline earths that are found in the precursor films are then compensated for by the addition of appropriate CaF2 and/or BaF2 films onto the surface of the precursor film. Post deposition annealing of the films is then done in an atmosphere of thallium oxide and oxygen in order to form the superconducting phases. The annealed films are examined using x-ray diffraction (XRD), an ac inductance technique, and critical current in an external magnetic field. XRD shows the c-axis length of the superconducting phase to increase as the overall film stoichiometry approaches 2212. The transition widths measured by inductive coupling weakly correlate with 77 K critical current measurements. Our best critical current results are 1.5*106 amps/ cm2 for a film measured at 4 K in an 8 T magnetic field (parallel to the films' c-axis).

We have used pulsed excimer laser radiation at 248 nm to mix Ti layers into Si3N4 substrates. Mixed layers show formation of small grain TiN in a Si3N4 but no evidence of Ti‐Si compounds or free Si. Low fluence (∼1.0 J cm−2) processing results in minimal mixing as TiN formation at the interface impedes further diffusion. At higher fluence (≳2 J cm−2) complete and quite uniform mixing occurs. The mixed layer is of the order of 0.5 μm thick.

Neutron reflectometry (NR) studies1 of thin films of amorphous 11B/l0B on silicon indicate that a non-standard form of Fickian diffusion occurs across the boron interface upon annealing. In order to verify this observation, the samples were examined by neutron depth profiling (NDP). Comparison of the results from models of a step function, standard Fickian diffusion and Fickian diffusion with a fixed composition at the interface were made and compared to the previous NR results. The diffusion constant resulting from the non-standard Fickian model for the NDP data differs slightly from that obtained from the commonly used Fickian diffusion model and is not inconsistent with the NR results. This finding suggests that more information regarding diffusion at interfaces can be gained from these higher resolution neutron scattering techniques.

We have begun a series of neutron reflectometry studies to investigate atomic diffusion behavior in both elemental boron and refractory transition-metal borides. In this paper, we report on the results for boron-atom self-diffusion in amorphous elemental boron. The samples used for the measurements were thin-film bilayer structures consisting of alternating layers of isotopically enriched 10B and 11B, deposited by electron-beam evaporation. The reflectometry studies were performed with a beam of pulsed neutrons having a broad thermal spectrum incident on the samples at an angle of approximately 1.00 degree(s). Specularly reflected neutrons were detected as a function of their time-of-flight with a position-sensitive detector. This data was reduced to obtain a plot of the reflectivity vs. the perpendicular wavevector. Because of the different nuclear potentials for the two boron isotopes, an interference pattern was observed, analogous to those obtained by X-ray measurements on samples with a modulated index of refraction. Reflectivity profiles were measured and analyzed as a function of annealing time for temperatures of 360 degree(s)C and 400 degree(s)C. Variations in the interference patterns were then used to determine the diffusion coefficient, D, at 360 degree(s)C, and hence the intrinsic diffusion parameters. A typical equilibrium result was determined to be D approximately 10-1 angstroms2s, measured at an annealing temperature of 360 degree(s)C. The measured diffusion constants are inconsistent with the high melting temperature of elemental boron, but are consistent with measured diffusion constants in other amorphous thin films.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Excimer laser surface processing of Ti-6A1-4V results in substantial surface oxygen incorporation as measured by the narrow resonance in the elastic scattering of a particles at 3.05 MeV. Single pulse processing at 1.0 J-cm−2 results in transformation from the original a + β grain structure to a martensite structure. Multiple pulse processing results in oxygen incorporation proportional to the number of pulses during processing, but this is primarily reflected in the depth of the oxygen containing layer. A maximum oxygen to titanium ratio of 1.0 was observed in the surface layer. This was confirmed by transmission electron microscopy (TEM) which showed the development of a fine-grained equiaxed TiO surface layer from a phase mixture of Ti alloy with TiO precipitates. Concentration vs. depth profiles show that this layer is approximately 400 nm thick after 40 pulses. Further processing with a total of 60 pulses results in coarsening of the grains and an increase in the thickness of the layer. The TiO precipitate concentration increases gradually, becoming apparent in electron diffraction patterns after 30 pulses. No other oxide phases are observed, the TiO developing directly from the metallic phases. In particular, we do not observe the formation of Ti2O prior to the formation of the TiO, or the formation of TiO2.

We have investigated the fabrication of thin-film superconductors by Cu-ion implantation into initially Cu-deficient Y(BaF2)Cu thin films. The precursor films were co-evaporated on SrTiO3 substrates, and subsequently implanted to various doses with 400 keV 63Cu2+. Implantations were preformed at both LN2 temperature and at 380°C. The films were post-annealed in oxygen, and characterized as a function of dose by four-point probe analysis, X-ray diffraction, ion-beam backscattering and channeling, and scanning electron microscopy. It was found that a significant improvement in film quality could be achieved by heating the films to 380°C during the implantation. The best films became fully superconducting at 60–70 K, and exhibited good metallic R vs. T. behavior in the normal state.

Thick (8 to 10 µm) Ba-Ca-Cu-O films have been rf magnetron sputtered onto Ag alloy (Consil 995) substrates. The films were given a post-deposition anneal in an over pressure of Ti in order to form the superconducting phases. Annealing protocols were done which result in predominantly the 1212 and 2212 phases. The substrate orientation was varied to determine its effect on film orientation. Material properties of the films were characterized by x-ray diffraction (XRD), ion beam backscattering spectroscopy, energy dispersive x-ray analysis (EDAX), and scanning electron microscopy (SEM). Electrical characterization of the films was done using dynamic impedance (DI) at 10 kHz and rf surface resistance (Rs) at 18 GHz in a TE011 fundamental mode cavity.

The Interfacial stability of a high strength TiB2/Cu multilayer structure was examined by subjecting the layers to ion irradiation by 400 keV Ne++ ions up to a maximum dose of 12×1015 ions/cm2. Even at the highest dose, with a maximum dpa value of 4.92, the TiB2/Cu interface did not show any mixing. This stability of the multilayers has been explained by examining the maximum thermodynamic driving force for Interfacial reactions in this system.

Angular distributions of sputtered atoms have been obtained for 3, 25, and 50 keV Ar+ bombardment of a liquid Ga-In eutectic alloy target. Sputtered material was collected on graphite foils which were subsequently analyzed by Rutherford backscattering spectroscopy, and the resulting distributions were fit by a functional form, N (θ) α. cos^nθ. For each energy, the angular distribution of sputtered In atoms was overcosine, with n_(In) ≈ 1.8 ±0.1. The distributions of the sputtered Ga atoms were sharper, varying from n_(Ga) ≈ 3.2 ± 0.2 at 25 and 50 keV, to n_(Ga) = 4.9 ± 0.3 at 3 keV. A comparison of the sputtered flux composition with the alloy surface composition profile gives F_1, the fraction of sputtered atoms originating from the first atomic layer. The fraction was found to be f_1 = 0.87 ± 0.01 for 25 and 50 keV bombardment, and increased to 0.94 ± 0.01 at 3 keV. The variations of n_(ga), and F_1 with projectile energy may be the result of a decrease in the average recoil-atom energy for the 3 keV bombardment. The large values found for F_1 support a prediction that the sputtered-atom escape depth is determined by the elastic-collision mean free path of recoil atoms.

Thin films of the Tl‐based superconductors often have relatively poor properties because of film/substrate interdiffusion which occurs during the anneal. We have therefore investigated the use of BaF2 as a diffusion barrier. TICaBaCuO thin films were deposited by dc magnetron sputtering onto MgO substrates, both with and without an evaporation‐deposited BaF2 buffer layer, and post‐annealed in a Tl over‐pressure. Electrical properties of the films were determined by four‐point probe analysis, and compositions were measured by ion‐backscattering spectroscopy. Structural analysis was performed by X‐ray diffraction and scanning electron microscopy. The BaF2 buffer layers were found to significantly improve the properties of the TICaBaCuO thin films.