Organic monocrystal-based FETs: electronical and structural studies

Molecule-based single crystals are promising materials for FETs applications, but usually special crystal growth conditions on the device surface are needed to obtain good samples. We prepared several single crystals starting from a commercial molecule, para-hydroxy-cyanophenol (HOPhCN), by a wet growing technique, and we investigated the correlations between the molecular packing and the anisotropy of the charge transport on the surface of organic crystals through measurements conducted between properly oriented contacts placed on the crystal. An anisotropic gate effect depending from the crystallographic orientation was found in single crystals of para-hydroxy-cyanophenol, grown from organic solution. Although with very low currents, this effect is well visible, and could be potentially exploited for fabricating bi-functional OFETs. In addition, also a response to white light illumination of the electrcical characteristics of the crystals was found, suggesting the that inside the crystals light-induced detrapping occurs. More work is presently being carried on in order to further investigate these phenomena, with particular reference to the gate anisotropic behaviour. Moreover, other organic molecules are being investigated in this sense