Ion—beam induced epitaxial crystallization (IBIEC) of amorphous N1Si2 and CoSi2 layers is demonstrated. Epitaxial metal suicide layers on (111) Si substrates were implanted with 40 keV Si ions to form amorphous surface layers. IBIEC of amorphous NiSi2 and CoSi2 layers was induced at 13—74°C with 1.5 MeV Ne ion irradiation and proceeded in a layer—by—layer manner from the original amorphous/crystalline interface with activation energies of 0.26 ± 0.07 and 0.21 ± 0.06 eV for N1Si2 and CoSi2, respectively.

Buried single-crystal YSi1.7 layers have been synthesized using high fluence implants of 330 keV yttrium ions into (111) Si held at 450°C followed by post-implant anneals of 1000°C . Rutherford backscattering spectrometry showed that an implant fluence of 3.6 X 1017 Y/cm2 forms a continuous layer of uniform thickness. Whereas, implant fluences of 1 — 2 x 1017 Y/cm2 form a thin continuous YSi1.7 layer with what are believed to be Y-silicide precipitates above and below the YSi1.7 layer. Strains resulting from the YSi1-7 layers were evaluated from x-ray rocking curves using a double crystal diffractometer.

Ion beam annealing of amorphous Si(100) layers formed by co-implantation of overlapping Ga and As distributions is studied. Annealing was done using 750 keV Si+ ions with the Si substrate held at 300°C. The samples were characterized using 2.0 and 5.0 MeV He+ backscattering/channeling as well as by transmission electron microscopy (TEM). Crystallization of the amorphous Si layer occurs during irradiation via solid-phase-epitaxial growth without impurity precipitation or segregation. Both the Ga and As are mainly substitutional in the Si lattice, even at concentrations in excess of 7 at. % for each species. These results are attributed to compensation effects, most likely through ion pairing of the dopants.

Both silicon and nitrogen implanted silica glasses were characterized by SIMS, XPS and SEM. Bubbles appeared in the implanted region at the high dose implantation (the silicon to nitrogen dose ratio is 0.75 and the total dose is 4×10 ions/cm2). Suppression methods of bubble formation were discussed concerning about the nitrogen implantation.

Ion irradiation and annealing studies were performed on Ni, Ni-20 at.%Al multilayers and Ni-20 at.%Al co-evaporated thin films. Xe+ ions were used to irradiate the films and homogenize the multilayers at room temperature. Irradiation of alloy films formed a metastable, supersaturated solid solution of γ phase and an HCP phase. Ion induced grain growth occurred in all films. A factor of 2 greater growth was observed in Ni-Al multilayers compared with coevaporated films irradiated to the same dose. The enhancement is attributed to a heat of mixing effect. Post irradiation annealing of the mixed multilayers formed γ*, the morphology of which was dependent upon the presence of Cu in the films due to substrate mixing from the support grid.

Conventional and high resolution electron microscopy were used to study structural development in silicon-on-insulator material produced by oxygen implantation at temperatures of 525 to 700°C, doses of 0.3 to 1.8 × 1018 cm-2, and current densities of 1 and 10 mA/cm2. Implantation temperature has the strongest effect on the microstructure and defect formation, both in as-implanted and annealed material. In the top silicon layer of as-implanted SIMOX, oxygen bubbles form near the surface when the wafer temperature is ≥ 550°C. A new type of defect, the multiply faulted defect (MFD), has been observed at the upper edge of the implantation region with a density of 108 cm-2 in the samples implanted at the temperature of ≥ 600°C. As dose increases from 0.3 to 1.8 × 1018 cm-2, the bubbles grow larger and the trails of bubbles lengthen while the character and density of MFDs remain the same. A continuous buried oxide layer forms at doses ≥ 1.5 × 1018 cm2. No significant difference in structure is observed when a current-density increases from 1 to 10 mA/cm2.

During the preparation of the substrates, involving ion implantation (> 1014 O* cm−2) and extended high temperature annealing (∼ 1350°C), many defects are unintentionally introduced, which can act as trapping and recombination centres. In this paper the carrier lifetime distributions and recombination kinetics determined by Photoconductive Frequency Resolved Spectroscopy (PCFRS) are reported. Comparative measurements of the lifetime distributions in bulk silicon, annealed bulk silicon and device quality SIMOX have been made. In annealed silicon and SIMOX higher order recombination kinetics are observed whilst, as expected, the kinetics are first order in unannealed bulk silicon.

Results of PCFRS measurements made as a function of temperature in the range 350 K to 150 K reveal a strong dependence of the lifetime distribution on temperature, confirming the dominance of carrier trapping. Trap parameters have been obtained from Arrhenius plots of the lifetime distributions.

A mechanism is proposed to explain ion-induced solid-phase epitaxial growth (SPEG). It is argued that radiation-enhanced diffusion in amorphous solid is the cause of ion-induced SPEG at relatively low temperatures. The atoms in the amorphous solid near the crystalline/amorphous interface adjust their positions to lattice sites due to a free energy decrease associated with the transformation from amorphous to crystalline solid. An expression for the velocity of ion-induced SPEG is derived. At low temperatures and high irradiation dose rates, a large number of atoms in the lattice gets displaced and the free energy of the crystalline solid can increase to such a value that the crystalline/amorphous interface may remain stationary. It is shown that the dose rate at which the interface remains stationary increases with the temperature, following an Arrhenius dependence.

We have studied the effect of implantation temperature, dose step, and total dose on the buried Si02 layer formed with a multiple low dose oxygen implantation process. Furthermore, we have produced a continuous, high quality buried SiO2 layer about 1500 Å thick with a dose of only 7 × 1017 0+/cm2 at 160 keV. The thin SiO2 layer is important not only because of the possible economic advantages of reduced dose, but also because a thinner oxide layer is more radiation hard.

The phase formation during ion-beam mixing of binary transition-metal alloys has been studied by use of Xe* , Ar* , and Ne* as a function of temperature and composition. Especially the composition ranges, where only amorphous phases occur, i.e., the glass-forming ranges, have been investigated. Based on semiempi-rical data on free energies, metastable phase diagrams have been constructed and glass-forming ranges estimated for the case of negative heat of mixing. Taking into account the quite large uncertainties of the applied thermodynamic data, reasonable agreement is observed between estimated and experimental glass-forming ranges. In the case of positive heat of mixing, the initial thin-film structure is near thermodynamic equilibrium. However, for small values of the heat of mixing, it is still possible to form amorphous structures. In the absence of chemical driving forces, this formation cannot be explained in a similar way as in the case of negative heat of mixing. As the nucleation of crystalline phases may differ with and without irradiation, irradiation of amorphous structures at elevated temperatures may create new metastable phases. Preliminary measurement of crystallization of metallic-glass films during irradiation are reported.

We combine chemical lattice imaging and digital vector pattern recognition to study quantitatively, kinetic intermixing in GaAs/AlAs multilayers. We thus obtain, with atomic plane resolution and near-atomic sensitivity, composition profiles across each interface of a multilayer stack before and after ion-implantation. Our results show significant intermixing even when only one 320 keV Ga+ ion is implanted at 77 K into each 2000 A2 area of the interface. This corresponds to an incident ion dose of 5×l012/cm2.

The intermixing is not uniform along the interface. At each interface, we observe more intensely intermixed regions, whose widths correspond to those created by the damage track of a single implanted ion, as expected from Monte-Carlo simulations. It thus appears that we can directly image intermixing due to single energetic ions implanted into the multilayered GaAs/AlAs structure.

The influence of implanted carbon on ion beam mixing of a Fe-Ti system was investigated. Carbon was introduced into bilayer samples by implanting 13C isotopes. The implantation energies were selected to set the mean range of carbon ions in either the iron or titanium layer. The effect of implanted carbon on 400 keV Ar ion mixing in the temperature range from 0 to 300 °C was studied using Rutherford backscattering spectroscopy at the energy of 5 MeV. Changes in carbon concentration profiles were probed utilizing the resonance of the nuclear reaction l3C(p,y)14N at the proton energy of 1.748 MeV. The measurements revealed that mixing was not affected by carbon implanted into the titanium layer. However, carbon in the iron layer remarkably retarded mixing at all temperatures investigated. Significant changes in carbon depth distributions were observed only when the sample with implanted carbon in the iron layer was mixed at 300 °C. These result are explained in terms of the enhanced mobility of carbon in an evaporated iron film which allows segregation to the interface. At low temperatures, however, vacancy-carbon interaction in iron may have a contribution to the retarded ion beam mixing.

Previous studies have shown that the presence of hydrogen in multilayer samples containing Ti reduces ion beam mixing rates. The present study sought to determine why the magnitude of this effect depends on which metal is mixed into Ti and why it is correlated to the rate at which hydrogen leaves the sample during mixing. Hydrogen loss rates of multilayers were compared with those of bilayer samples designed to minimize the effect of mixing. For bilayers, hydrogen loss rates were smaller and did not depend on which metal was mixed into Ti in the same way that multilayer loss rates do. This suggests that hydrogen leaves the multilayer samples because it is bound less strongly in the mixed regions than in the Ti. The primary cause of hydrogen loss is mixing rather than ion beam induced desorption.

Interdiffusion of Fe and B trilayer specimens during 1-MeV Kr+ bombardment was studied using Rutherford backscattering and electron microscopy. The square of the interdiffusion distance during mixing at 300°C was found to depend linearly on the irradiation dose. Arrhenius behavior with an apparent activation enthalpy of 0.7 eV was observed for the mixing between 200 and 500°C. Electron microscopy of ion-beam mixed multilayer specimens revealed that two crystalline compounds, Fe2B and Fe3B, formed during bombardment at 450°C, while two different amorphous Fe/B phases formed at 300°C. Substantially improved adhesion and reduced friction were observed for Fe/B multilayers ion-beam mixed onto M50 steel substrates at 450°C.

The I—V characteristics of as—deposited antimony Schottky contacts on silicon were extremely sensitive to interface conditions. This led to unpredictable results for the unimplanted contacts. After Si* implantation the contacts displayed more uniform I—V characteristics. Implantation led to higher values for the ideality constant, the series resistance and for the saturation current. The ideality factor seems to decrease at the higher implantation doses (ϕ ≥ 5×1014 Sb+cn−2), while no clear dose dependence patterns were observed for the saturation current and series resistance after implantation.

Ion beam mixing of a Pd/Cu bilayer is studied using irradiation with 80 keV Ar+ ions at room temperature. RBS analysis shows that intermixing has occurred across the Pd/Cu interface, and that the mixing amount increases with increasing ion dose, which agrees well with a model for radiation enhanced diffusion. It is found that the Cu3Pd phase grows in a layer-by-layer manner.

Ion beam mixing (with 150 keV 1016 Ar ions/cm2) of multilayered Co-B films with various bilayer periods (BP = TCo + TB, TCo = 4 × TB), and layer thickness ratios, was studied to determine its utility, compared to sputtering, in producing morphological changes in amorphous thin films. All the ion beam mixed films were amorphous, but the morphologies of both the as-deposited and the ion beam mixed films varied with the BP. The in-plane, easy axis anisotropies of the films with the largest BP were obliterated by mixing, although their hard axis coercivities were unchanged. The anisotropy of the films with smaller BPs was increased by mixing. The results indicate that ion beam mixing is a potentially useful method of improving the properties of soft magnetic thin films.

A cermet coating was obtained on a silicon-deposited pure iron surface by means of a single treatment integrating ion implantation and ion beam mixing. As conpared with either simple ion implantation or simple ion beam mixing,the integrated treatment provides the cermet coating with an electrochemical performance far better than the simple treatments.

Ion implantation at room temperature of lead into aluminium leads to spontaneous phase separation and formation of lead precipitates growing topotactically with the matrix. Unlike the highly pressurised (∼ 1–5 GPa) solid inclusions formed after noble gas implantations, the pressure in the lead precipitates is found to be less than 0.12 GPa.

Recently we have observed the intriguing result that the lead inclusions in aluminium exhibit both superheating and supercooling [1]. In this paper we review and elaborate on these results. Small implantation-induced lead precipitates embedded in an aluminium matrix were studied by X-ray diffraction. The (111) Bragg peak originating from the lead crystals was followed during several temperature cycles, from room temperature to 678 K. The melting temperature for bulk lead is 601 K. In the first heating cycle we found a superheating of the lead precipitates of 67 K before melting occurred. During subsequent cooling a supercooling of 21 K below the solidification point of bulk lead was observed. In the subsequent heating cycles this hysteresis at the melting transition was reproducible. The full width of the hysteresis loop slowly decreased to 62 K, while the mean size of the inclusions gradually increased from 14.5 nm to 27 nm. The phenomena of superheating and supercooling are thus most pronounced for the small crystallites. The persistence of the hysteresis loop over successive heating cycles demonstrate that its cause is intrinsic in nature, and it is believed that the superheating originates from the lack of free surfaces of the lead inclusions.

Non-equilibrium Molecular Dynamics simulation methods have been used to study the trapping of “impurities” in an Ag5B15 Lennard-Jones alloy where the B atoms are 10% bigger in diameter than A. The observation of surface melting in this system is used to calculate an equilibrium interfacial segregation coefficient. Simulations of rapid melting and resolidification were performed for the (100) and (111) orientations at two different substrate temperatures (0.65 Tm and 0.95 Tm) for each orientation. Solute impurity atoms are shown to have been trapped at greater concentrations in the solid than under equilibrium conditions. Partitionless solidification is observed when the regrowth velocity greatly exceeds the diffusive velocity.