Computer simulations of the collision cascade process were used to investigate surface densification during ion beam assisted deposition (IBAD). The objective of the investigation was to see if densification resulted directly from the cascade, without any contribution from diffusion enhancement brought on by the bombardment. Calculations, using the computer code MARLOWE, were carried out for Ar bombardment of a crystalline Ge target, containing a void, using ion beam energies of 0.065, 0.5 and 1 keV. These results were used as data for a differential equation that describes the effect on void size of the simultaneous Ge atom deposition and Ar ion bombardment of a substrate containing voids. The present attempt examined the effects of irradiations on voids of 17 and 35 vacancies.

Displacement cascades formed in a silicon crystal by As+ and Si+ ions with energy in the range 50–500 eV are constructed with a molecular dynamics and a Monte Carlo simulation method. Conspicuous spike effects are observed with the molecular dynamics simulation.

A thermal spike analysis was utilized to predict the time evolution of energy propagation through a solid resulting from energetic particle impact. An analytical solution was developed that can predict the number of surface excitations such as desorption, diffusion or chemical reaction activated by an energetic particle. The analytical solution is limited to substrates at zero Kelvin and to materials with constant thermal diffusivities. These limitations were removed by developing a computer numerical integration of the propagation of the thermal spike through the solid and the subsequent activation of surface processes.

The mathematical model of a combined film deposition and and high dose ion implantation for coating formation has been developed. Calculations of concentration profiles of implanted element in the film and substrate depending on different parameters of the model have been carried out.

Migration energies in Ag of vacancies, interstitials, Zn impurity atoms, interstitial-iipurity cumplexes, and vacancy-impurity complexes were calculated using Embedded Atom. Method (EAM) potentials in Molecular Statics calculations. A new Zn EAM potential was determined and used in these calculations. The dependence of the migration energies on local defect concentrations was determined in a linear approximation. Binding and formation energies of defects are also presented. A new model for the migration energy appropriate for defect reactions is introduced.

This paper deals with the implantation of molecular ions in silicon. The ‘molecular’ effect, i.e. the increase of the displacement yield compared with the sum of the atomic yields, is weak for light molecules (e.g., H2) and for heavy diatomic molecules (e.g., Sb2 and Bi2), but, for instance, it is strong for C6H6 at energy per atomic mass of the order of 1 keV/amu. Binary collision calculations are used to give a pictorial view of the phenomena occurring along the ion path, and to predict superadditivity and damage columnarity. The increase of pressure and temperature to extreme conditions by implantation of molecular ions is discussed.

Diffusion in a thermal spike is shown to be the dominant mechanism for both high- and low-energy ion mixing. The similarity between high- and low-energy ion mixing is the result of the fractal nature of collision cascades.

A semi-empirical model for ion mixing at low temperatures was developed taking into account collisional mixing and thermal spike effects, as well as the thermal spike shape. The collisional mixing part was accounted for by the Kinchin-Pease model, or, alternatively dynamic Monte Carlo simulation. For the thermal spike, the ion beam mixing parameter Dt/Φ is derived as being proportional to χ2+μ, where the damage parameter is defined as, χ = − F0/ΔHcoh, F0 is the damage energy deposited per unit path length, and μ is a constant dependent on the thermal spike shape and point defect density in the thermal spike regions. The shape of the thermal spike that best fit the experimental results depends on the magnitude of the cascade density. For relatively high density collisional cascades, where thermal spikes start to be important, it was found that a spherical thermal spike model was more consistent with experimental measurements at low temperatures. However, for extremely high density collisional cascade regions, a cylindrical thermal spike gave better results. Finally, three different regions of ion beam induced mixing were recognized according to different density levels of damage energy scaled by the damage parameter χ.

Concentration dependent migration and reaction migration energies, calculated with the molecular dynamics code DYNAMD using Embedded Atom Method Potentials, were inserted into the appropriate diffusion and rate coefficients. The time and space evolution of the concentration of interstitials, vacancies, Zn impurity, interstitial-inpurity, aid vacancy-impurity complexes was calculated for an irradiated AgZn alloy in the framework of the approach presented in Johnson and Lam. A significant effect on defect segregation and profiles was found.

Previous comparisons of the room temperature mixing of Ni-Ti and Fe-Ti multilayers have shown significant differences in the mixing rates in spite of closely similar heats of mixing as well as ballistic properties. This result suggests contributions from mechanisms other than ballistic and thermal spike effects, or a break-down of present thermal spike models for these materials. In order to identify the mixing mechanisms involved, quantitative measurements were made at various temperatures between 80K and 350K using bilayer samples. Surprisingly, the mixing rates were found to disagree significantly with those estimated for multilayer samples.

Crystalline Fe and Fe-10at.%Ti and amorphous Fe-37at.%Ti films with Ag and Hf markers were produced by vapor deposition. Marker spreading during ion-beam mixing between 77 K and 580 K was measured using Rutherford Back-scattering (RBS). Marker spreading was also measured between temperatures of 300 K to 700 K after full crystallization of the Fe-37at.%Ti films. Microstructural changes during ion-beam mixing were studied in situ, in a High-Voltage Electron Microscope. Homogeneous nucleation of a metastable bcc phase, was observed at high temperatures. The results are discussed in terms of their relevance to “radiation-enhanced” diffusion in amorphous materials.

A qualitative study of ion beam mixing of multilayers has shown that the presence of hydrogen in the sample slows mixing considerably for Fe/Ti, and slightly for Ni/Ti. We have quantified this effect and extended the study to four more systems (Co/Ti, Pd/Ti, Ti/Cu, and Ti/Al) and to lower temperatures. The degree to which H charging reduced the mixing rate varied substantially with multilayer system. H was lost during mixing. H was lost fastest from those films for which the H effect was the smallest. Our data are consistent with a model that relates mixing inhibition to H-vacancy binding energy in the non-Ti component.

The first observation of a new class of icosahedral phase associated with a magnetic transition in Fe-Cu and Fe-Mo systems are reported. It is found that the icosahedral order can be re-established when the destabilized Fe60Cu40 icosahedral phase subject to a magnetic transition at high annealing temperature. The Fe70Mo30 amorphous films obtained by sputtering exhibit a similar behavior at high magnetic transition temperature. A brief discussion of the observed phenomena is addressed.

The triode sputtering technique and a “split-target” arrangement were used to produce metastable crystalline and amorphous phases in the Cu-W, Mo-Cu, Ag-Fe, Ag-Cu, Pu-Ta and Pu-V systems. These systems all exhibit liquid and solid immiscibility and have positive heats of mixing and atomic radii that differ by at least 10%. The sputtered coatings, whose thickness varied between 25 and 200 microns, were formed at deposition rates between 35 and 200 Å/s. They were characterized using x-ray diffraction, TEM, microprobe, microhardness, and DSC techniques. The observed amorphous and metastable solid solution phases are discussed in terms of predicated heats of formation for these phases using Miedema's thermodynamic approximations [1] that include chemical, elastic, and structural contributions. Differences in compositional ranges observed by high rate sputter deposition compared to other vapor deposition techniques (e.g., coevaporation) appeared to arise as a result of processes that occur during deposition or immediately following deposition.

A study was performed to investigate the morphology of amorphous alloys which were formed on the surface of the samples by means of ion beam bombardment. The specimens of Fe deposited with Cr, Ti, Cr-Ni or Cr-Ni-Cr multilayers were bombarded by high doses of Ar+, N+ or Ti+ ion beams respectively. TEM and electron diffraction analysis were then used to study the kinetic transformation of amorphous to crystal during heating. The electro-chemical results hlvn showed after that the anodic current density Ic and Im were reduced remarkably.

Amorphous Si/Ge artificial multilayers with a repeat length of around 60A have been partially mixed with 1.5 MeV Ar+ ions at temperatures in the range 77–673K. The change in the intensity of the first X-ray diffraction peak resulting from the composition modulation is used to determine the mixing lengths. The diffusive component of the square of the mixing length, at a given dose, is independent of the dose rate and has an Arrhenius-type temperature dependence, with activation enthalpies between 0.19 and 0.22 eV, depending on the average composition.

The systematics of ion beam induced intermixing of WSi0.45 on GaAs have been studied after through-implantation of Si or O in the dose range 1013 − 5 × 1016 cm−2. SIMS profiling shows significant knock-on of Si and W into the GaAs at the high dose range in accordance with Monte Carlo simulations, but there is virtually no electrical activation (≤0.1%) of this Si after normal implant annealing (900°C, 10 sec). This appears to be a result of the high level of disorder near the metal-semiconductor interface, which is not repaired by annealing. This damage consists primarily of dislocation loops extending a few hundred angstroms below the end of range of the implanted ions. Extrapolation of the ion doses used in this work to the usual doses used in GaAs device fabrication would imply that ion-induced intermixing of WSix will not be significant in through-implantation processes.

Thermally and ion-induced reactions of transition metals Zr, Ti, Cr and Ag with CuO substrates have been studied by Rutherford backscattering spectrometry and X-ray diffraction techniques. Reactions resulted in the configuration of ZrO2/Cu2O/CuO from Zr/CuO structure and TiOx/Cu2O from Ti/CuO structure after thermal annealing and ion irradiation. No significant reaction has been found in Cr/CuO after vacuum annealing at 410°C and 300 Key Xe ions irradiation at 240°C. Ag atoms balled up on CuO surface after annealing at 610°C. A comparison of the reaction layers has been made in both metal/SiO2 and metal/CuO systems after thermal annealing and ion irradiation. Both heats of reaction and bond strength in the substrates can influence the chemical reactivity between metal layer and substrate.

The design of the necessary multilayer structures for producing superconducting thin films by ion beam mixing methods requires, among others, the knowledge of the individual (binary) mixing rates. In order to measure these, various combinations of Y, Ba, Cu, and Bi were irradiated with 600 keV Xe-ions at 80K and 300K. The systems exhibited a wide range of mixing behaviors which are also of fundamental interest. Ba and Cu readily formed the BaCu phase, and further mixing with Cu progressed only via binary collision mechanisms. At 80K Cu and Y were rapidly mixed in any ratio by thermal spikes, whereas a Cu rich sample rapidly formed the Cu6Y phase at 300K. Ba could not be mixed into Y or a Y-Cu mixture. Finally, irradiation of polycrystalline layers of Cu and Bi apparently lead to rapid motion of Bi along grainboundaries at both temperatures.

The angle of incidence of ion bombardment is an important processing parameter, which can strongly affect the shape, composition and microstructure of bombarded surfaces. We describe several phenomena directly related to the angle of ion incidence during ion beam etching and ion beam assisted deposition. First, the development of surface ripple topography during ion beam etching is modeled. Surface perturbations are shown to grow under ion bombardment, while surface selfdiffusion acts to select a characteristic wavelength. The orientation of these characteristic ripples changes by 90° as the angle of ion incidence is varied from near-normal to near-glancing angle. The second example is the effect of angle of incidence on the etching rate of Ta under mixed Ar-O2 ion bombardment. For pure Ar bombardment, the sputtering yield of Ta increases with angle of ion incidence slower than secθ, producing a maximum etch rate at normal incidence. Above a critical pressure of O2, however, the yield increases faster than secθ dependence, producing a maximum etch rate at a non-normal angle of incidence. The third example is the effect of angle of incidence on the preferential sputtering of Al relative to Cu in Al-5% Cu thin films. Films deposited by evaporation with simultaneous Ar ion bombardment at 500 eV show a depletion of Al relative to Cu. This composition change is enhanced by increasing the angle of incidence away from normal, resulting in a higher Cu concentration in a film deposited on a tilted surface. Finally, a mechanism is described for the generation of oriented microstructure in films deposited under simultaneous glancing-angle ion bombardment, demonstrated previously for Nb. Grain orientations are selected which allow channelling of the ion beam. These results show that the shape, composition and microstructure of films deposited under ion bombardment respond to changes in angle of incidence, and that these effects need further study and modeling.