No abstract

No abstract

No abstract

Single crystal Cu͑001͒ layers were grown on MgO͑001͒ by ultrahigh vacuum magnetron sputtering at T s = 100°C. Quantitative surface morphological analyses by in situ scanning tunneling microscopy show that the surfaces exhibit self-affine mound structures with a scaling exponent of 0.82Ϯ 0.03 and a mound radius r c that increases from 31Ϯ 8 to 39Ϯ 6 nm for increasing layer thickness t = 24-120 nm. In situ annealing at 200 and 300°C leads to a thermodynamically driven mass transport that minimizes the surface step density, resulting in broader mounds and a smaller root mean square surface roughness. This effect is most pronounced for t = 24 nm, for which r c increases from 31Ϯ 8 to 70Ϯ 20 nm and decreases from 1.3Ϯ 0.1 to 0.74Ϯ 0.08 nm, resulting in a decrease in the average surface slope from = 7°to 2°and an increase in the average terrace width w T by more than a factor of 4. In contrast, w T increases by only 20% for t = 120 nm. This remarkable difference between "thin" and "thick" layers is attributed to diverging surface morphological pathways during annealing: The strong smoothening for t = 24 nm is due to a competitive coalescence process where some mounds grow laterally at the expense of their smaller neighbors, which die out. In contrast, the initially wider mounds of thicker layers ͑t = 120 nm͒ combine to form a quasistable surface morphology that exhibits anisotropic mound structures, which limit mass transport and stabilize the surface step density.

Coatings are very important for numerous industrial applications such as increasing the wear resistance of tools, providing thermal conductivity to components in engines or electric conductivity in microelectronic devices. The mechanical properties of the coatings are of prime concern. The practicability of performing miniaturized compression tests in order to determine mechanical properties of various thin films was analysed. Four coatings, a polycrystalline tungsten coating, a single crystal copper coating and two single crystal hard coatings (vanadium nitride and titanium nitride) were tested. The compression samples were fabricated using a focused ion beam microscope. The compression tests were executed with a micro-indenter installed in a scanning electron microscope. The deformation of the sample was observed and in-situ recorded by scanning electron microscopy. From the measured load-displacement data true stress-true strain curves were calculated. The limits and benefits of the microcompression technique are discussed. Durchführung von Mikro-Druckversuchen an dünnenSchichten: Vor-und Nachteile. Hochwertige Werkzeuge werden beschichtet, um sie einerseits verschleißbeständiger zu machen und um andererseits die benötigten Werkstoffeigenschaften für das jeweilige Einsatzgebiet zu erhalten. Ähnliche Optimierungsstrategien werden z. B. bei thermischen Schutzschichten für Turbinenschaufeln oder elektrisch leitfähigen Schichten in der Mikroelektronik verfolgt. Für die Anwendungen ist es notwendig, die mechanischen Eigenschaften der jeweiligen Schicht zu kennen. Es werden die Durchführbarkeit von Mikro-Druckversuchen an vier verschiedenen Beschichtungen, an einer polykristallinen Wolframschicht, an einer einkristallinen Kupferschicht und an zwei einkristallinen Hartstoffschichten (Vanadiumnitrid und Titannitrid) analysiert und die Vor-und Nachteile der Methode diskutiert. Mit Hilfe eines Rasterionenmikroskops wurden kleine Druckproben aus den jeweiligen Schichten gefertigt und anschließend mit einem Mikro-Indenter, welcher in ein Rasterelektronenmikroskop eingebaut wurde, geprüft. Die Verformung der Druckproben wurde während des Druckversuches beobachtet und aus den aufgezeichneten Kraft-Verschiebungswerten wurden wahre Spannungs-wahre Dehnungskurven berechnet.