In order to perform a systematic study of the interaction between grain boundaries (GBs) and dislocations using molecular dynamics (MD), several tools need to be available. A combination of computational geometry and MD was used to build the foundations of what we call a virtual laboratory. First, an algorithm to generate GBs on face-centered cubic bicrystals was developed. Two crystals with different orientations are placed together. Then, by applying “microscopic” rigid body translations along the GB plane to one of the crystals and removing overlapping atoms, a set of initial configurations is sampled and a minimum energy configuration is found. Second, to classify the geometry of the GBs a local symmetry type (LST) describing the angular environment of each atom is calculated. It is found that for a given relaxed GB the number of atoms with different LSTs is not very large and that it is possible to find unique geometrical patterns in each GB. For instance, the LSTs of two GBs having the same “macroscopic” configuration but different “microscopic” degrees of freedom can be dissimilar: the configurations with higher GB energy tend to have a higher number of atoms with different LSTs. Third, edge dislocations are introduced into the bicrystals. We see that full edge dislocations split into Shockley partials. Finally, by loading the bicrystals with tensile stresses the edge dislocations are put into motion. Various examples of dislocation-GB interactions in Cu are presented.

Metal/polymer system joints are widely encountered nowadays in microscopic structures such as displays and microchips. In several critical cases they undergo thermal and mechanical loading, with contact failure due to fracture as a possible consequence. Because of their variety in nature and composition metal/polymer joints have become major challenges for experimental, theoretical, and numerical studies. Here we report on results of molecular dynamics simulations carried out to study the mechanical response of a metal/polymer joint, in this case the Cu/polybutadiene model system. The behavior of Cu and the cross-linked polybutadiene are modeled, respectively, by the Embedded Atom Method (EAM) and the Universal Force Field (UFF). Loading is applied under compression. Different potentials are used to describe the interactions in the metal/polymer interface, which allows us to qualitatively analyze possible mechanisms of failure in these joints, below the metal melting point and above the polymer glass transition temperatures.

Point defects and thermal stability of ultrathin Cu films (3–200 Å) deposited on Mo(110) substrate at 300 K have been characterized using thermal helium desorption spectrometry (THDS). Implantation of the samples (10–100 Å Cu/Mo) with 1000 eV He+ aided in detecting He release from monovacancy in Cu films and desorption of the films (above 1200 K) from Mo substrate. A thickness dependent peak is identified in the helium desorption spectra, which is shown to be due to the process of island formation in the Cu films, using pre-implantation annealing treatments for the 40 Å film. Native defects in the films (3–200 Å) were probed using 75 eV He+ implantation.

Molecular Dynamics simulations were performed to study Cu film deposition on β-Ta. Three different β-Ta surfaces were used, two being atomically flat, and one resulting from Ta on Ta growth. We find that the Cu films develop a (111) texture with vertical grain boundaries between grains having different epitaxial relations with the β-Ta substrate. The epitaxial rotation angles were determined, as 5.2° and 10-13°, and the resulting strain reductions in the Cu films were identified. The effects of the substrate differences on the interfacial Ta/Cu intermixing and the epitaxy and grain boundary structure of the films are discussed.

Molecular Dynamics computer simulations were used to explore a number of complex phenomena that occur during film growth and ion-surface interactions. A few examples are discussed. (1) Strong surface patterns develop when a Mo film is grown on a Mo(110) substrate, whereas they are absent for Mo on Mo(100). (2) Depositing a Mo film on a substrate containing two antiparallel (100)/(910) grain boundaries leads to complicated film morphologies in the grain boundary regions. Stresses, mosaic spread, and regions of fcc Mo are observed, and their stability is examined. (3) Cu films deposited on a Mo(110) substrate, a model system for interconnects in modern IC technology, are affected by the strong fcc/bcc interface mismatch. The Cu film properties are analyzed for thermally evaporated films and for films grown by argon ion-beam assisted deposition (IBAD).

We report on the simulation of the growth and subsequent krypton ion polishing of thin molybdenum films, required for extreme ultraviolet multilayer mirror fabrication. We have used a comprehensive Molecular Dynamics (MD) code, principally enabling a simulation of the deposition, ion bombardment and annealing processes. Ion energies used are in the sub-keV range, and the ion angle of incidence is varied between 30 and 60 degrees off-normal.

The effects of ion polishing on the surface roughness are discussed, as well as the increase in (surface) atom mobility. We also report data on sputtering yields, ion penetration depths, trapping, energy transfer and krypton implantation and saturation.

The results are compared with TRIM results, and the relevance of MD and TRIM simulations for specific purposes is discussed. Also, the effects of short-time, high-temperature annealing of an amorphous film are investigated.

Using He+ as probe particles, we have studied point defects in Mo thin films (5-1000 Å) deposited without and with Ar+ ion beam assistance (0.2–22 eV per Mo atom). It is found that the net effect of the ion beam is to produce rather than to annihilate point defects. Ar incorporation is only slight (-10-4). Annealing of the films leads to the thermal production of polyvacancies.

Molecular dynamics simulations of glassy Ni81B19,starting with a configuration obtained by the Reverse Monte Carlo Method,indicate a calorimetrie glass transition at 960 K and point to a significantchange in the atomic dynamics between 960 and 1200 K. Above this range,normal liquid-like behavior is found; at lower temperatures, we find aresidual diffusivity and cooperative atomic Motion. Atomic jumps areprocesses smeared out in time and space over continuous rather than discretescales.

Diffusion-induced phase transformations were studied in Ni/β-Ta multilayers between 523 K and 823 K, primarily using x-ray diffraction. The multilayers had a modulation length, A, of 20.3 nm and a composition of Ni48Ta52. They were polycrystalline without coherency between the Ni and Ta sublayers. Upon annealing at relatively low temperatures (up to 723 K) Ta dissolved in crystalline Ni, concurrently with the formation of an amorphous phase. The interdiffusion reactions did not take place only at the Ni/Ta interfaces, but also along the grain boundaries in the sublayers. The chemical diffusion coefficient in the amorphous phase was determined at 673 K, using a previously developed method. The results were compared with experiments on Ni/Ti multilayers, which show similar reactions. At 723 K and higher temperatures the fcc (Ni, Ta) solid solution transformed into the stable Ni3Ta compound.