Effect of a plasma polymerised linalyl acetate dielectric on the optical and morphological properties of an n-type organic semiconductor

Abstract

Thin films of the n-type, organic semiconductor PDI-8CN2 were thermally evaporated on two different dielectric surfaces and their optical and morphological properties investigated using Variable Angle Spectroscopic Ellipsometry (VASE) and Atomic Force Microscopy (AFM), respectively. The two dielectric surfaces used were SiO2 and a plasma polymer derived from the non-synthetic monomer linalyl acetate. The characterisations were performed in order to assess the viability of plasma polymerised linalyl acetate (PLA) thin films as dielectric layers in future Organic Field-Effect Transistor (OFET) devices. These studies resulted in determination of the optical profiles (refractive index and extinction coefficient) in the UV-Vis band of PDI-8CN2 grown on SiO2 and an observation of uniaxial anisotropy in the organic semiconductor. This information is useful for the design of opto-electronic devices using PDI-8CN2 layers. Variations in morphological properties and small variations optical properties were found when the PDI-8CN2 films were grown on PLA layers, and attributed to the change in surface chemistry between dielectrics.