ja981232p_si_001.pdf (177.37 kB)
Preparation, Characterization, and Properties of Mixed Organic and Polymeric Self-Assembled Multilayers
journal contribution
posted on 1998-08-15, 00:00 authored by DeQuan Li, M. Lütt, M. R. Fitzsimmons, R. Synowicki, M. E. Hawley, G. W. BrownMultilayer thin films consisting of layer-pairs of oppositely charged macrocycles (nickel phthalocyanine tetrasulfonate, NiPc) and macromolecules (poly(diallydimethylammonium) chloride, PDDA) were
fabricated using self-assembly techniques. The film structures were characterized with X-ray reflectometry,
from which the roughness (∼2−7 Å) of the film growth surface, the average electron density of each layer-pair, the mean thickness of the layer-pairs (∼10.5 Å), and the overall thickness of the multilayer samples were
deduced. Measurements of film thicknesses were applied as constraints to an analysis of spectroscopic
ellipsometry measurements of the films. Imposition of these constraints increased the confidence of the optical
constant refinements deduced from ellipsometry. We find, for multilayers of PDDA and NiPc, a refractive
index of n ≈ 1.6−1.8 in the nonabsorption region of the visible and near-infrared (IR) spectrum and an extinction
coefficient in close agreement with the measured electron optical absorption at 630 and 665 nm. Atomic
force microscopy was also used to observe surface morphology and determine grain size distribution and
roughness for selected films. An increase in surface roughness (∼5−15 Å) was observed as the number of
layer-pairs in the film increased from 3 to 27.