<title>Electrical and structural properties of LB multilayers of (methylacylamino) azobenzenes</title>

Abstract

The present publication is devoted to the studies of the structure of the Langmuir-Blodget films of (methylacylamino)azobenzene derivatives and their electrical properties. Structural studies of monolayers have been carried out by Atom Force Microscopy. The molecules are closely packed in an hexagonal crystalline array. UV irradiation causes a rearrangement of the molecules and a significant structural modification in the monolayer are observed in the frontier region between two crystalline domains of different orientations. The anisotropy of dc conductivity is observed in multilayer assemblies. A low dc conductivity in the bulk ofsample ofthe order of1lO'°1O'3 S/cm is obtained. In the case of in-plane conductivity the value of conductivity is of the order of lO8lOb0 S/cm. The several sets of hole trapping states are situated at energy depth of E=0.55±0.03eV and E =0.48±0.03eV with the value of the total density of given set of traps of the order of 1012 cm3. The frequency dependence of capacitance and conductance is nonlinear, with capacitance values decreasing exponentially with higher frequencies while the conductance increases gradually. The behavior is one typical for low mobility materials and the conduction mechanism can be explained in terms of hopping conduction between localized states. The linear dependence of dc in-plane conductivity on relative humidity was observed.