Tuesday, May 20, 2008, 1:00 pm — Small Seminar Room, Bldg. 510
One of the most important challenges in the fabrication of artificially structured oxide materials is to increase the layer-by-layer (LBL) growth rate while maintaining atomic level precision. From a purely kinetic standpoint the formation of sharp interfaces during film growth is determined by the interplay of two atomic surface transport processes:
intralayer transport, also known as surface diffusion, and interlayer transport, which describes the ability of adatoms to descend a step edge. Thermally driven growth processes offer no mechanisms for selectively controlling a particular surface transport process. Because of their ability preferentially to excite specific degrees of freedom, energy enhanced growth processes can promote a particular surface transport mechanism with a dramatic effect on the growth kinetics. According to recent theoretical work the nonequilibrium nature of such processes is manifested in the dissipation of energy by fast lateral motion of the excited species during a thermalization stage referred to as transient mobility (TM). A unique feature of TM is that surface migration is not restricted to hopping from site-to-site because the energy of the atoms exceeds the surface migration barrier. The best known examples of film growth enhancement by energetic growth species are provided by the dramatic surface smoothing in pulsed laser deposition (PLD). However, it is surprising that average PLD growth rates do not substantially exceed MBE growth rates indicating that PLD is not truly operating in a nonequilibrium regime. This situation exists solely because of the long held belief that thermal processes are the only way to induce crystallization and control surface morphology in LBL growth.
In this talk I describe the use of time-resolved surface x-ray diffraction to study atomic surface transport in epitaxial growth of SrTiO3 by PLD. We use a CCD camera to measure the entire diffraction intensity map at the (0 0 ½) reflection. From these
Hosted by: Ivan Bozovic
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