  Our study aims at a better control and understanding of the transfer of a
complex [DNA supercoiled plasmid - dodecyltrimethylammonium surfactant] layer
from a liquid-vapour water interface onto a silicon surface without any
additional cross-linker. The production of the complexed layer and its transfer
from the aqueous subphase to the substrate is achieved with a Langmuir-Blodgett
device. The substrate consists of a reconstructed boron doped silicon substrate
with a nanometer-scale roughness. Using X-ray photoelectron spectroscopy and
atomic force microscopy measurements, it is shown that the DNA complexes are
stretched in a disorderly manner throughout a 2-4 nm high net-like structure.
The mechanism of transfer of this layer onto the planar surface of the
semi-conductor and the parameters of the process are analysed and illustrated
by atomic force microscopy snapshots. The molecular layer exhibits the typical
characteristics of a spinodal decomposition pattern or dewetting features.
Plasmid molecules appear like long flattened fibers covering the surface,
forming holes of various shapes and areas. The cluster-cluster aggregation of
the complex structure gets very much denser on the substrate edge. The
supercoiled DNA plasmids undergo conformational changes and a high degree of
condensation and aggregation is observed.

Chemical Physics