Epitaxial beryllium films and beryllium-based multilayer mirrors for soft x-rays.
AuthorRuffner, Judith Alison.
Committee ChairFalco, Charles M.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractEpitaxial Be films and Be-based multilayers were fabricated and characterized for a variety of deposition conditions. Epitaxial Be films were grown for the first time on α-Al₂O₃ (0001), Si (111), Si (100), GaAs (111), and Ge (111) single-crystal substrates. The effects of the substrate material, substrate temperature, deposition rate, and post-annealing temperature on the crystalline quality of the epitaxial Be films were studied. All of the resultant epitaxial films exhibited the hexagonal close-packed (hcp) Be crystal structure. Epitaxial Be films which were grown on substrates with hexagonal lattices [α-Al₂O₃ (0001), Si (111), GaAs (111), and Ge (111)] invariably grew with their hexagonal lattices parallel to the substrate plane. In nearly all cases, the Be hcp lattice grew in the anticipated best-fit epitaxial relation with the substrate. The crystalline quality of the Be films improved significantly with increasing substrate temperature. However, Be films deposited at substrate temperatures ≥ 400°C were discontinuous, and many exhibited hexagonal-shaped crystallites. The deposition rate had no effect on crystalline quality over the range studied (3.1-18.5 Å/min). Annealing epitaxial Be films at temperatures ≤ 625°C after deposition improved crystalline quality only slightly. Annealing the films at 700°C resulted in the collapse of hexagonal grains in order to relieve stress within the film. The highest quality epitaxial Be films were deposited onto Si (111) substrates maintained at 300°C. The crystal quality was improved further by annealing the sample at 300°C for 30 minutes after deposition. These samples exhibited the first known (2 x 3) reconstruction of the Be (0001) surface. The design and fabrication of several Be-based multilayer mirrors for use at soft x-ray wavelengths (λ = 10-500 Å) was also investigated. Germanium and bismuth were selected as the absorber material candidates for the Be-based multilayers. The Ge/Be combination resulted in a multilayered structure. This multilayered growth combined with the epitaxial growth of Be lays the foundation for fabrication of single-crystal multilayer (superlattice) mirrors for soft x-rays.
Degree ProgramOptical Sciences