We report on the functionalization of silicon oxide nanostructures using luminescent dye molecules and the
characterization of these systems by optical microscopy. The nanostructures are prepared by local anodic oxidation
(LAO) of a dodecyl-terminated silicon substrate using an atomic force microscope (AFM). The silicon oxide
nanostructures are negatively charged and the cationic dye rhodamine 6G could be successively bound to the structures
by electrostatic interactions. A quenching of luminescence due to the interaction of the excited states with the silicon was
found. The luminescence signal is attributed to monomeric Rh6G molecules with a slight blue shift of the emission due
to the changed chemical environment.
We report the creation of nano-structures via Dip Pen Nanolithography by locally exploiting the mechanical response of
polymer thin films to an acidic environment. Protonation of cross linked poly(4-vinylpyridine) (P4VP) leads to a
swelling of the polymer. We studied this process by using an AFM tip coated with a pH 4 buffer. Protons migrate
through a water meniscus between tip and sample into the polymer matrix and interact with the nitrogen of the pyridyl
group forming a pyridinium cation. The increase in film thickness, which is due to Coulomb repulsion between the
charged centers, was investigated using Atomic Force Microscopy. The smallest structures achieved had a width of about
40 nm. Different control experiments support our claim that the protonation is the reason for the swelling and therefore
the formation of the structures. Kelvin probe force microscopy measurements suggest the presence of counter ions which
compensate the positively charged pyridinium ions. We investigated the influence of the water meniscus on the structure
formation by varying the relative humidity in the range from 5% to 60% for different dwell times. The diffusion of
protons and counter ions is humidity-dependent and requires a water meniscus.
Positive and negative charges are stored locally in thin films of silicon oxide on silicon by applying a voltage between an
AFM cantilever tip and the silicon substrate. The stored charges are displayed by Kelvin probe force microscopy
(KPFM). The process of charge storing is investigated with respect to different dwell times and different voltages. The
amount of stored charges increases both with applied voltage and dwell time. A decay mechanism of the charges with
two different time regimes is discussed. A fast decay is attributed to a migration parallel to the surface, while the second
one is dominated by a transport perpendicular to the substrate surface.