J. R. Skuza

CdS thin films formed on flexible plastic substrates by pulsed-laser deposition

The merger of a transparent plastic foil substrate with a semiconductor CdS film for a photonic application was realized using pulsed-laser deposition. Although plastic is not considered to be a favoured substrate material for semiconductor thin-film formation, the deposited CdS film possesses good adhesion, with a polycrystalline texture, flat surface (roughness/thickness = 0.003), and room-temperature photosensitivity with a blue-shifted peak at 2.54 eV. This work demonstrates the capability of pulsed-laser deposition to form novel heterostructures with appealing and useful technological properties such as plasticity and low weight.

Optimizing the planar structure of (1 1 1) Au/Co/Au trilayers

Au/Co/Au trilayers are interesting for a range of applications which exploit their unusual optical and electronic transport behaviour in a magnetic field. Here we present a comprehensive structural and morphological study of a series of trilayers with 0–7 nm Co layer thickness fabricated on glass by ultrahigh vacuum vapour deposition. We use a combination of in situ electron diffraction, atomic force microscopy and x-ray scattering to determine the optimum deposition conditions for highly textured, flat and continuous layered structures. The 16 nm Au-on-glass buffer layer, deposited at ambient temperature, is found to develop a smooth (1 1 1) texture on annealing at 350 °C for 10 min. Subsequent growth of the Co layer at 150 °C produces a (1 1 1) textured film with lateral grain size of ~150 nm in the 7 nm-thick Co layer. A simultaneous in-plane and out-of-plane Co lattice expansion is observed for the thinnest Co layers, converging to bulk values for the thickest films. The roughness of the Co layer is similar to that of the Au buffer layer, indicative of conformal growth. The 6 nm Au capping layer smoothens the trilayer surface, resulting in a surface roughness independent of the Co layer thickness.

Real time structural modification of epitaxial FePt thin films under x-ray rapid thermal annealing using undulator radiation

Modification of chemical order in epitaxial FePt binary alloy thin films deposited on MgO (100) substrates was induced and investigated in real time using x-ray rapid thermal annealing (XRTA). This is possible because synchrotron undulator radiation has sufficient power density to induce significant structural modifications in thin films and its energy can be tuned to optimize absorption in the sample. A monochromatic portion of the pink beam diffracted from the epitaxial FePt sample was used to probe microstructure evolution in real time and significant changes in chemical order were observed. In particular, the relative amount of L10 phase remained practically unchanged whereas the amount of L12 phase was significantly decreased in the FePt thin film sample during XRTA.

Highly ordered FePd and FePt nanostructures

In the present study we show two variations of the bottom-up approach. First our correlated structural and magnetic properties studies on epitaxial FePd films grown on (001) MgO will show that this particular system does exhibit perpendicular magnetic anisotropy and it is also nano-structured due to 3-dimensional growth mode on the chosen substrate. We also note here that the highly-ordered nanostructures embedded in the chemically disordered alloy film are magnetically coupled. We found that capping the films with a thin MgO layer significantly lowers interparticle coupling. For the FePt system we have used ion-implantation of Fe ions on epitaxial Pt films followed by rapid thermal treatments. We have achieved controlled nano-patterning, large perpendicular magnetic anisotropy and decoupled highly ordered nano-structures. We present our correlated structural (XRD, AFM, TEM) and magnetic (MFM, Kerr magnetometry) characterizations on the two systems studied. Our observations are useful to further understand magnetic anisotropy properties at the nano-scale for new media applications.