DEPOSITION SYSTEM FOR THE SYNTHESIS OF MODULATED, ULTRATHIN-FILM COMPOSITES

We have initiated a program using elemental superlattices as probes of the early stages of solid-state reactions. The main advantage of using superlattices as reactants is the ability to tailor their structure on an angstrom length scale to control reaction kinetics. Consequently, we designed and constructed a computer-controlled and monitored ultrahigh-vacuum chamber for the preparation of elemental superlattices. This system is capable of manufacturing three sets of three samples in one evacuation cycle. Up to six different elements can be incorporated into each sample. Elements can be deposited from independently controlled electron-beam sources, Knudsen, or evaporation cells. The sample drive mechanism combined with source shutters and computer control permit complex layer-repeat units within the composite. Layer thicknesses can be controllably varied from 4 A upward. Various attributes of the chamber include its modular design, multiple layer thickness control options, reproducibility and quality of samples, flexibility, and extensive computer monitoring during sample preparation.