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Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P135
Growth Mode of ZnPc on Passivated and Bare Silicon Substrates
Sindu John Louis 1 , Daniel Lehmann 1 , Marion Friedrich 1 , Dietrich R.T.
Zahn 1
1 Chemnitz University of Technology, Semiconductor Physics, D-09107 Chemnitz, Ger-
many
Zinc Phthalocyanine (ZnPc) has been identified as an excellent candidate, because of
its flexibility in varying electrical and optical behaviour and its own benefit as an organic
semiconductors. It is known that the fashion of ZnPc molecular stacking, affects
its electrical and photoconductivity, which depends on the degree of π-π interaction between
the adjacent molecules. Being planar and exhibiting structural self organisation,
the molecular orientation depends mainly on the growth mode of the first few layers,
which in turn depends on the inter molecular interaction and on molecule-substrate
interaction.
Thin films of ZnPc are prepared by Organic Molecular Beam Deposition (OMBD) in
ultra high vacuum condition on hydrogen passivated and bare silicon (111) oriented
substrates. Spectroscopic ellipsometry and transmission measurements are carried out
using Variable Angle Spectroscopic Ellipsometer (VASE) in the NIR-Vis-UV range
from 0.75 eV to 5 eV. For the optically anisotropic ZnPc films, the complex dielectric
function, film thicknesses and the surface roughness were determined. The average
molecular tilt angle of the ZnPc with respect to the substrate is calculated. The
results are confirmed with infrared reflection measurements.
Both the dielectric function as well as the tilt angle of the ZnPc molecule is found to
be strongly dependent on the substrate used. The kind of orientation adopted by the
first few layers is found to be preserved in thicker films.