Structural and Morphological Characterization of an Organic Multilayer Photodiode with X-ray Scattering Techniques, SEM and AFM
Alfred Neuhold
16:00 - 17:00 Tuesday 19 October 2010 KFU

Organic opto-electronic devices such as light emitting devices as well as organic photodiodes (OPDs) are generally constructed by sandwiching organic thin films between two metal electrodes. The growth of the different layers on top of each other occurs in a specific manner. In our case the OPDs consist of several stacked layers of a thin semitransparent gold layer, a copper phthalocyanine layer (CuPc) (hole transport layer), a perylene tetracarboxylic bisbenzimidazole (PTCBI) layer, an aluminium-tris(8-hydroxychinolin) (Alq3) layer (both electron transport layers) and a silver top electrode. All these layers were vacuum deposited at room temperature, except for the gold electrode, which was deposited by sputtering. The used substrate was on the one hand thermally oxidized silicon (SiOx) and on the other hand a flexible foil (Mylar).

Several techniques were used to extract information about the thickness of the individual layers, the surface morphology, and especially the evolution of the roughness after the individual layer deposition. For this purpose different samples were investigated where the deposition was stopped after each layer in order to be able to get access to the layer surface. These morphological studies were then combined with the crystallographic structure of the layers. Different microscopy techniques like scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning force microscopy (AFM) were used and combined with X-ray scattering techniques, like X-ray reflectivity (XRR) yielding layer thickness values and grazing incidence X-ray diffraction (GIXD).