| Surfaces having well-defined morphologies like periodic arrays of dots or lines, promise useful applications. Magnetic nanodots of Co and Fe-alloys are useful in patterned magnetic recording media. Well controlled grain size and surface area of nanostructured TiO2 are useful to develop efficient photocatalysts. However, there is a continuing need to develop techniques to make such surfaces in a simple and economical manner.; In this thesis, a previously unexplored in-situ approach to assemble lateral patterns in thin films was proposed and investigated. Simple models of film growth on a defect free surface show that under uniform areal deposition rates and surface temperatures, nucleation occurs at random positions on the surface. We proposed that by exposing a growing thin film to a spatially varying surface temperature distribution, nucleation and growth can be confined to specific spatial locations. Consequently, a film with a desired pattern or thickness modulation could be achieved.; The experimental approach consists of irradiating the substrate surface with a laser interference pattern simultaneous with physical vapor deposition (PVD). To perform such film growth experiments, a vibration minimized and multifunctional ultra-high vacuum chamber was integrated with a Nd:YAG laser. The laser output is a beam of 266 nm with a coherence length of approximately 2 m and an area of ∼0.8 x 0.8 cm2. The laser has a pulse width of 9 ns, a constant repetition rate of 50 Hz, with a rated peak output of 44 mJ/pulse. The typical laser energy density used in this work was about 10 mJ/cm2. Since sub-micron length scales were of interest, vibration studies were performed by recording the interference patterns on kapton films. Results from the kapton films, measurements using a shear accelerometer and recent growth results showed that peak-to-peak vibration amplitudes on the substrate surface were less than +/-25 nm.; Well-established PVD techniques like pulsed laser deposition and electron beam evaporation were used to deposit Ag, Co or TiOx thin films on to single crystal Si(100) substrates. Typical deposition rates used in this work were 0.1 to 1 nm/min. Simultaneous deposition with irradiation of the Si surface with two-beam interference patterns resulted in films with periodic thickness modulations, producing line-like structures. (Abstract shortened by UMI.)... |
