We succeeded in synthesizing MoN-TiN superconducting artificial superstructure film (SASF). The structure of MoN layers is estimated to be γ-Mo2 N. The behavior of Tc in SASFs is recognized by a proximity effect using adjustable parameters of bulk Tc. Calculated parameters are, however, different from Tc of single layered films.

Superlattice superconductors exhibit behavior different from other “homogeneous” superconductors because of their layered structures. Sputtering has proved to be an excellent technique for producing such multilayered systems. Also, systems naturally having layered structures, such as the new high-Tc materials, can be fabricated by sputtering. Here we describe the preparation of superconducting superlattices by dc triode sputtering and techniques useful for characterizing them. In particular, we discuss Mo/Ta superconducting superlattices and high Tc thin films of YBa2Cu3O7-x.

Upper critical fields of graphite-KHg multilayers with 10Å periodicity were measured as a function of angle and temperature. The Hc2 (θ, T) data were compared to the anisotropic Ginzburg-Landau model and were found to be in qualitative agreement, except at the lowest reduced temperatures, where significant deviations are found. The primary deviations from the anisotropic GL model are first, that the values of the critical field at the lowest temperatures are found to be higher than that predicted by the model, and secondly, the critical field anistropy ratio is found to be temperaturedependent. These deviations are discussed in light of more detailed models of anisotropic superconductivity.

The appropriate application of multilayers as x-ray dispersion devices requires that their diffraction characteristics be understood. Conventional models, based on perfect-crystal and mosaic-crystal theories, predict diffraction efficiencies (integral reflection coefficients) significantly larger than values measured experimentally. It has been shown that introduction of surface roughness effects into the model can promote agreement between experimental and theoretical values, while the presence of other types of defects produce changes too small in magnitude to explain the discrepancy. Because it is reasonably well agreed that the resolving power of multilayers is only moderate, compared to the more conventional “crystal” dispersing devices, it is important to be able to predict or measure that parameter in order to assess the usefulness for a particular application. Experimental measurements and theoretical calculations have been carried out on multilayers (almost exclusively tungsten/carbon) prepared to have 2d-spacings from 50 to 140A. The experimental work used both singlecrystal and double-crystal spectrometers; the calculations used the crystal diffraction model, as modified to include surface roughness.

Multilayers are man-made microstructures engineered to vary in depth that are now of sufficient quality to be used as x-ray, soft x-ray and extreme ultraviolet optics. Gratings are in-plane man-made microstructures which have been used as optic elements for most of this century. Joining of these two optical elements to form combined microstructure optics has the potential for greatly enhancing both the resolution and the throughput attainable in these spectral ranges. Experimental results for multilayer gratings are presented and discussed. It will be demonstrated that multilayer diffraction gratings act as x-ray prisms and are high efficiency dispersion elements.

Enhancements in the elastic moduli by factors of two or more in compositionally modulated metallic thin films have been observed for a certain range of composition modulation wavelengths. The experimental and theoretical understanding of this phenomenon, known as the supermodulus effect, is reviewed. Also, the mechanical properties of other artificially layered and composite materials are discussed and compared with the behavior of metallic superlattice thin films.

The relationship between microstructure and physical behavior is especially pronounced in synthetic multilayer materials. Insight to the mechanisms responsible for changes in the mechanical properties can be investigated through a careful examination of the multilayer microstructure. A dominant feature of the nultilayer structure is the interface. The population of interlayer boundaries, that is interfaces, is directly proportional to the multilayer period for any given film thickness. In this paper, we will evaluate “TEM” images of multilayer systems. The interface structure will be viewed in cross-section and a range of layer thicknesses will be considered. Variation in the elastic modulus, yield stress, and microhardness have been observed for noble-transition metal systems over a wide range of multilayer periods, from less than 1 nm to greater than 1000 nm. In epitaxial systems, the extent of superlattice perfection (coherency effects) is closely tied with changes in physical behavior. Emphasis will thus be placed on the str'ucture and strain distribution from the interface, and its role in determining the mechanical properties of multilayers.

Magnetic superlattices serve as model systems for the study of thin film, interfacial, proximity, coupling and superlattice phenomena. Due to these phenomena, the physical properties of magnetic superlattices can be tuned in a reproducible fashion by proper control of the preparation process.

Magnetic measurements in conjunction with detailed structural characterization provide a fruitful area of research, especially in understanding basic phenomena in magnetism. We describe here briefly a few experimental examples from our work which illustrate the possibilities magnetic superlattices offer for the study of basic phenomena in magnetism.

Interconnections are predicted to become the limit in performance and reliability at submicron dimensions. Layered structures are one possible solution to the problems of electromigration and hillocks. Aluminum alloys can improve the properties of pure aluminum but with a consistent increase in resistivity due to lattice distortions introduced by the alloy in solid solution. The rise in resistivity is minimal in layered films because aluminum layers act as parallel conductors. Titanium is the most effective refractory metal for eliminating hillocks in layered films; however vanadium, tantalum, and tungsten also reduce hillocks to a manageable level although high resistivity, the inability to dry etch, or lateral hillocks can become a problem. Layered films of aluminum with TiSi2 encounter problems with hillocks. These differences are partially explained by the increased strength of the aluminide TiA13 that forms compared to the other compounds. Barrier metals are needed for aluminum layered with refractory metals because of the formation of ternary compounds, and several metals have proven to be satisfactory. Such barriers, however, are required for even aluminum at submicron dimensions for stable low-resistivity contacts.

The reflection of monochromatic x-rays by a layered heterostructure can be utilized as a nondestructive probe to obtain information on the interfacial roughness in the material. Interference between x-rays reflected from the top surface and the interfaces can give rise to pronounced oscillations in the reflectivity as a function of the grazing incidence angle. We have made use of this technique to investigate the interfacial roughness in semiconductor heterostructures grown by molecular beam epitaxy.