Tesis Doctorado
Growth, structure, phase transitións and desorptión kinetics of n-dotriacontane films
Autor
Volkmann, Ulrich G.
Pontificia Universidad Católica de Chile
Institución
Resumen
In this work we present studies of thin n-dotriacontane (C32) films deposited by
physical vapor deposition (PVD) onto Si(JOO) substrates with their native silicon oxide
layer. To have a good comprehension of this system we studied importani properties of
the film due to the interaction with the substrate. We analyzed the growth mode of the
film during deposition. the structure of the samples after deposited, the phase transitions
in temperature. and the desorption kinetics of the system.
To study the films growth during deposition, we monitored in-silu and in real
time the adsorption of the molecules with high-resolution ellipsometry. We have found
that the increase in roughness during film growth depends on the deposition rate and on
the substrate temperature.
The structure of the vapor-deposited films vas studied by Atomic Force
Microscopy (AFM) and x-ray reflectivity (XRR). Films grew with a bilayer adjacent to
the S102surface in which the C32 molecules are aligned with their long axis parallel to
the interface followed by upper layers of perpendicular molecules. The occupancy of
the layers depends mainly on the substrate temperature during deposition.
Using AFM and XRR. we also studied phase transitions of the alkane films. We
found that the perpendicular layers are unstable to the formation of bulk particles when
sample is heated aboye the bulk melting temperature. We observed that on heating, but
below bulk melting point, the perpendicular layers of the film present a lessening in
thickness. We were also able to obtain information from a transition of the parallel
bilayer that occurs ahoye the hulk melting temperature. Finaily. we investigated the desorption kinetics of C32 films from the Si0 2
surface in thermally programmed desorption experiments. We found that the desorption
mechanism of the parallel layer adjacent to the substrate is divided into two steps.