Julia Martynczuk

Actinic damage of Y/Mo multilayer optics in a table-top plasma-driven x-ray laser

A Y/Mo multilayer coating, optimized for top reflectivity at λ=12  nm, has been nano-inspected after long-term operation at the in-house soft x-ray laser. The surface and optical inspections were complemented by electron microscopy on cross sections, prepared with focused ion beam technology. A factor of 2.5 loss of reflectivity in the exposed area (ca. 30% relative loss every 100 shots), with concomitant nanoscale photodamage and particle fallout, was found. The x-ray-laser-induced damage extended as deep as 250 nm beneath the surface and as wide as the millimeter spot size.

Self-Limited to Parabolic Grain Growth Kinetics in Metal Oxide Thin Films

Distinctive microstructure engineering of amorphous to nanocrystalline electroceramic thin films is of high relevance for integration in low to high temperature operating MEMS-devices. Up to now, kinetic rules of nucleation, crystallization and grain growth of precipitation-based ceramic thin films are unknown. In this study, general rules for the crystallization and grain growth kinetics of a pure single-phase metal oxide thin film with only one kind of cation, i.e. ceria, made by spray pyrolysis from a precursor with one single organic solvent is discussed [1,. The near-and long range disorder is studied via Raman, DSC investigation of crystallization enthalpy, XRD, SEM and TEM for amorphous to fully crystalline state. These 400 nm thick-thin films were dense, crack-free and amorphous directly after deposition on a sapphire substrate. Briefly, above deposition temperature crystallization sets in with respect to temperature and persists over a broad temperature range from 400 to 950°C. In this regime, biphasic amorphous-crystallien films exist and grain growth proceeds simultaneously to crystallization. Isothermal grain growth studies showed that after short dwell times of 10-20h stable microstructures established following self-limited grain growth law [. In this state, driving force for the crystallization is the reduction of free enthalpy for phase transformation and interface diffusion prevails. A transition to classical grain curvature-driven parabolic grain growth kinetics appeared once the material reached the fully crystalline state for average grain sizes larger than 140 nm and higher annealing temperatures. Volume diffusion was then activated in addition to the interface diffusion. It was found that once crystallized the material shows independent on processing route equal XRD density and microstrain, as well as Raman characteristics. However, dependent on processing conditions i.e. choice of organic and, according, deposition temperature of the film amorphous states vary and affect strongly crystallization and grain growth history for the biphasic films.