The superconducting properties of high temperature superconductor (HTS) thin films fabricated using the BaF2 process are dependent on the quality of the substrate used to grow these films. In order to maximize the lattice matching between the superconducting film and the substrate, we have used a YBa2Cu3O7, thin film deposited on <100> SrTiO3 as a template. The first film was prepared by co-evaporation of Y, BaF2 and Cu on <100> SrTiO3, followed by an anneal in “wet” oxygen at 850 °C. This film showed a sharp transition at about 90 K. A thicker layer of about 5000 A was then deposited on top of this first 2000 Å film, using the same procedure. After the post anneal at 900 °C, the transition took place at 82 K and no epitaxy of the second film was observed. Ion beam mixing at 400 °C, using 400 keV O ions was done at the interface of the two films (the second one being not annealed). After the post anneal, the film displayed an improved Tc at 88K. Moreover, epitaxial growth was observed to take place at the ion mixed two-layer interface which was dose dependent. These results suggest that the homoepitaxy of the second layer on the first is interface limited and can be enhanced by ion mixing treatments.

High purity silica (Spectrosil) samples were implanted with Ti, Cr, Mn, Fe and Cu at doses ranging from 1.0 to 5.0×1015 ions/cm2 at 160 keV and 2.6 μA/cm2. The optical absorption extinction coefficients per ion were measured from 1.8 to 6.0 eV. In all samples there was an increase in absorption over the unimplanted sample at energies ≥4.6 eV. The increase in absorption at 5.1 eV and 5.7 eV is attributed to B2(E”) centers and E’ centers respectively. The relative values of the extinction coefficients of these bands are attributed to the relative oxygen activities of the TMI relative to the SiO2 host substrate.

Single crystalline substrates of LiNb03 have been implanted with 48Ti ions at 200 keV and doses up to 4 × 1017 cm−2. The implants have been performed at wafer temperatures of 77 K, 300 K and 620 K. Immediate subsequent processing at 1273 K in wet oxygen ambient led to good epitaxial regrowth at all doses, if sufficient time was allowed. The maximum observed extraordinary refractive index change after regrowth Δne=0.04, indicating a solubility limit of 3.3×l021 Ti cm−3 corresponding to 18 % of Nb5+ replaced by Ti4+.

X-cut substrates of LiNbO3 have been implanted at 500°C with Ti and O to doses of 2.5 and 7.5×l017 ions/cm2, respectively. The high substrate temperature during implantation ensures dynamic recrystallization, preserving the crystallinity of the LiNbOs-The stability of the stoichiometric implants is enhanced sufficiently that annealing at 1000°C proceeds with no surface degradation of the substrate. Annealing under identical conditions without the 0 implant usually results in phase separation of an oxide at the surface, even when annealing is performed immediately following implantation. Samples implanted with Ti and O to preserve the stoichiometric metahoxygen ratio of the substrate can be stored at room temperature for several months without phase separation. Planar optical waveguides have been produced by stoichiometric implantation followed by annealing in water-saturated oxygen for one hour at temperatures of 900 and 1000°C. The sample annealed at 900°C supported a single lossy mode, while the 1000°C sample supported two propagating modes and one lossy mode at λ=0.6μm.

Microhardness measurements were carried out on ion implanted single crystal Y2O3 stabilized cubic ZrO2. Ions were implanted up to fluences of 3×1017 ions/cm2. Comparison of the Knoop micro-hardness values of ZrO2 implanted with various species over a range of fluences showed that the principle variable causing hardness changes for inert ion implantation is damage energy and not the ion fluence nor the ion species. For shallow inert ion implants, the hardness versus damage energy gives a unified plot. Hardnesses rise with increasing deposited damage energy to a value 15% higher than that of unimplanted zirconia. With additional damage the hardness drops to a value 15% lower than that of the unimplanted zirconia. Deep implants showed 50% increases in hardness and significant fracture toughness increases.

Friction and wear measurements of the shallow implants in a pin-on-disk assembly showed very different behavior for high dose versus unimplanted ZrO2. The unimplanted samples showed debris with an associated rise in friction. The implanted system showed much less debris and a constant value of friction even after 10,000 cycles.

Isothermal annealing behaviour of intrinsic amorphous layers produced by stoichiometric implantation in a—axis oriented α—Al2O3 single crystals has been studied. The amorphous phase transforms directly to α—Al2O3 at a well defined planar interface which moves towards the free surface. The epitaxial growth slows down after initial rapid crystallization, indicating two separate regimes. The interface velocity shows Arrhenius behaviour in both regimes with activation energies of 0.6 and 0.08 eV respectively. There is an evidence for additional surface or random crystallization into κ or γ-Al2O3 phases within the first few nm on the surface, after prolonged annealing. These results are remarkably different from those reported previously for c–axis oriented Al2O3 crystals, showing the importance of substrate orientation during crystallization. A tentative model to explain the crystallization behaviour is discussed.

Al2O3 and ZrO2 substrates were coimplanted with 175 keV Mo+ and 74 keV S+ at doses of 1×10 cm−2 and 2×1017 cm−2 respectively. The energies of Mo+ and S+ ions were chosen to provide a nearly overlapping depth profiles in both substrates. Rutherford backscattering (RBS), Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) techniques were used for characterization. The as implanted surface of Al2O3 became amorphous while as implanted ZrO2 surface remained crystalline. The MoS2 phase was observed in the as implanted ZrO2. The MoS2 phase was observed in the implanted region of Al2O3 and ZrO2 after furnace annealing at 700°C. Thermodynamic calculations were performed to predict the equilibrium binary phase formed in Al2O3 and ZrO2 under the present implant and annealing conditions. The predictions agree with the experimental findings.

Implantation of iron Into α-Al2O3 at 77 K produces an amorphous state for fluences greater than about 3 × 1016 Fe/cm2. Iron in the as-implanted (amorphous) specimens is distributed among two Fe2+, two Fe4+, and the Fe° states. The conversion electron Mössbauer (CEMS) spectra for a sample containing 7 × 1016 Fe/cm2 show all iron to be converted to Fe3+ after annealing in oxygen for 1 h at 700°C and above. The transmission electron microscopy (TEM) shows the structure to be mostly Y-A120, after the 900°C anneal and all α-Al2O, after the 1100°C anneal.

A mechanism of amorphization by ion implantation in ceramic oxides is studied using a rate theory approach. It is proposed that the production of highly localized lattice distortions causes lattice destabilization and the ensuing transition to the amorphous state. These distortions can be caused by a large point defect buildup. It is argued that point defect retention occurs because of the impossibility of producing antisite defects. It is proposed that point defects on each sublattice can shield or trap point defects on the other sublattice. Similarly, metallic impurities may shield oxygen vacancies or trap oxygen interstitial ions, preventing anion Frenkel pairs from recombining. These effects are modeled in a-alumina for low temperature implantations (e.g., around 78 K), where point defects are immobile. It is shown that, at these temperatures, recombination is strongly hindered by the radiation-induced point defects themselves, rather than by the implanted impurities. The high point defect concentration attained by this mechanism is sufficient to raise the free energy of the crystal above the free energy of the amorphous solid.

The implantation of B and N into fused silica can result in chemical incorporation into the glass with a consequent larger increase in refractive index than is possible due to volume compaction alone. B implantation produces anomalously large concentrations of oxygen-vacancy defects which aid in the establishment of B into a borosilicate layer. N implants can result in unreacted N accumulations in addition to N incorporated into a Si-oxynitride layer. The unreacted N can also be incorporated by implantation damage (e.g., Si, Ar, Kr)--before or after N implantation--which provides additional occupancy sites. These results are important with respect to the use of implantation-produced waveguides for optoelectronic devices.

Electron irradiation damage in the metal monoxide series of group Vll and VIII elements -NiO, CoO, MnO and FeO - has been investigated in the non-UHV electron microscope environment. NiO and CoO were also examined in the UHV environment. Each of these materials showed comparatively similar electron-stimulated oxidation of the surface in the non-controlled conventional HREM environment, at a vacuum level of approximately 10–7 Torr; while only ballistic damage was observed in both the NiO and CoO under UHV conditions.

Thin foils of bulk YBa2Cu3O7–x (YBCO) superconductors were subjected to electron irradiation in a Transmission Electron Microscope (TEM). The resulting disordering of the oxygen atoms and vacancies in the Cu-0 planes was monitored by measuring the splitting of the (110) diffraction spots in the [001] diffraction pattern. Samples were irradiated at 83K with 100, 150, 200 and 300kV electrons. The 100kV electrons did not cause any disordering, even after prolonged irradiation. The results of the higher energy irradiations showed an excellent fit to a disordering model, indicating a lack of radiation assisted reordering at 83K. This was further confirmed by the insensitivity of the disordering to the dose rate of 300kV electrons at 83K. However, at 300K, an increase in the dose rate of 300kV electrons increased the disordering rate, indicating that radiation assisted reordering was occuring at that temperature.

Laser-induced vaporization of ceramics shows promise as a technique for the deposition of thin films of these materials. Critical to the utility of this technique is an understanding of the laser-material interaction, plume formation and dynamics, material transport and how variations in the vaporization conditions affect the deposited film. Lead zirconate titanate (PZT, Zr/Ti-47/53) targets were irradiated using a q-switched Nd:YAG laser (15 ns, 100 mJ at 1.064 /μm) . The deposition chamber was maintained at a pressure of 100 mTorr oxygen. Material from the plume was collected on silicon wafer substrates, suspended 1.0 - 3.0 cm above the target. The films were characterized by SEM/EDX, TEM, x-ray diffraction and electrical measurements before and after annealing. Very thin films were deposited on carbon coated metal grids for observation in the TEM using a hot stage to study crystallization. Temporally and spatially resolved spectra of the light emitted by the laser-generated plume were obtained with an optical multichannel analyzer (0MA) to yield information on the plume generation and chemistry of the deposition process. These spectra indicate that under these conditions a plasma is created above the target surface which persists for -100 ns after the laser pulse.

Three types of ions with different atomic masses (B , Ar and As ) were chosen to irradiate polyimide films in similar conditions in order to check mechanisms of the formation of ion beam induced damage in polyimide. A four-point probe technique was used to measure sheet resistivities of implanted films. An ion mass effect on conductivity of ion irradiated polyimide film was discovered. The ion mass effect on ion beam induced change of conductivity and on the energy loss process of the ions in polyimide suggest that the electronic energy loss of incident ions is an important factor for the increase of conductivity of implanted polyimide, and the contributions of recoil ionization are restricted by the grave damages as a result of nuclear energy loss process of ions in targets. Our hypothesis is supported by automatic spreading resistance measurement of B implanted polyimide film coated on silicon substrate. The results of this work have been compared with the hypothesis of degradation through direct knock on of atoms in polyimide, proposed by D.Fink et al [Nucl. Instr. and Meths B32 (1988) 125]

Radiation damage in V2Os induced by electrons in the energy range 0-3 keV has been studied by high resolution electron microscopy, X-ray photoelectron spectroscopy and mass spectrometry. Different phase transformations were observed when V205 was irradiated by electrons of different energies. The damage kinetics and the role of electron radiation enhanced diffusion were investigated. It was found that nucleation and growth of lower oxides was driven by electron radiation enhanced diffusion.

Dual ion implantations of Ti+ and C+ into sintered a-SiC and hot pressed SÌ3N4 have been studied by Rutherford backscattering spectroscopy (RBS) combined with plan/cross section view transmission electron microscopy (TEM). The samples were analyzed before and after annealing at 1200°C for 2 hours in a vacuum of 1x10-6 torr. The results were compared with single ion implantation of Ti+. RBS analysis showed that no oxidation occurred during annealing and Ti diffused toward the surface in both SiC and SigN^ Cross section TEM analysis revealed the formation of TiC precipitates in SiC due to both dual (Ti+ + C+) and single (Ti+) ion implantations. Precipitates were found to form in SÌ3N4 as well; however, because of very close proximity of observed d values with those of TiC, TiN and β-SiC, it was not possible to uniquely identify the chemical nature of these precipitates. Thermo-dynamic calculations were performed to explain the observed results.

The influence of γ-radiation on LaCoO3, for the catalytic decomposition of H2O2 has been studied. ESR and XPS studies of γ-irradiated LaCoO3, snowed, the formation of chemisorbed oxygen (O2) and reduction of Co2+ to Co . γ-irradia]:ion of LaCoO3. causes a decrease in electrical conductivity due to the trapping of charge carriers by the chemisorbed oxygen. SEM photographs of the Y-irradiated sample pellets reveal surface cracks and surface corrosion due to the diffusion of transition metal to surface. The enhancement in the catalytic activity for the decomposition of H2O2 is found to be directly proportional to the reduced metal content.

We discuss the amorphization process of semicrystalline and oriented PET (Polytethyleneterephtal ate)) thin toils by ion beam irradiation. P decrease in the bombarded samples melting point and enthalpy of fusion in the bombarded samples, as analysed by Differential Scanning Calorimetry (DSC), is associated with changes in the crystalline morphology and with an increase in the polymer disordered regions. Those facts are confirmed atso by a large decrease in the main X-ray diffraction peak amplitude as the tluence increases. P model of ion induced amorphization originally constructed for metals and semiconductors 11,23 was applied and cross-sections tor the process were obtained. The experimental data are well fitted using this model based on amorphization through the overlap of damage clusters, but an exclusive elastic collisions mechanism for the damage production cannot be inferred. As expected the electronic stopping mechanism also plays an important role in the polymer amorphization process.

Oxygen ion beam bombardment has been studied as a means for incorporating oxygen into thin films of Y-Ba-Cu-oxide either by enhancing the transport of oxygen to substrates during ion-beam sputtering, or by direct incorporation of oxygen with ion-assisted deposition. Optical emission spectroscopy was used to study the ion-beam bombardment of bulk superconducting targets as the oxygen content of the ion beam was varied. This study showed that oxygen did not directly combine with metallic elements in the target to increase the oxygen content of the stream of particles moving toward the substrate. Addition of a second ion beam directing oxygen ions toward the substrate during film growth caused large variations in the stoichiometry of the deposited films. At low oxygen ion currents, no increase in the oxygen content of the films was detected, while at relatively high currents, the oxygen incorporation increased. However, the sputtering of the metallic components of the film increased as the oxygen beam current increased, leading to very low growth rates.

Crystallization processes during thermal annealing have been studied for a number of group III, IV and V impurities implanted into amorphous Si. At high impurity concentrations, an amorphous to polycrystalline transformation is observed. For low solubility, low melting point species, this transformation is melt-mediated, whereas it can occur in the solid phase for other species such as Sb.