Poster titles

Abstract

Alkyl phosphonic acids (CnPA) are becoming a material of choice for passivation of high-k oxides in organic thin-film transistors with ultra-thin gate dielectrics. A monolayer of phosphonic acid inserted between the inorganic oxide and the organic semiconductor provides two main benefits: (i) the density of the charge carrier traps associated with the surface –OH groups of the oxide is reduced because these groups act as binding sites for the organic molecules; and (ii) the low surface energy of the organic monolayer may reduce the density of defects in the subsequently deposited conjugated polymer. To date such monolayers have been assembled from solutions only. We have recently developed a vapour-phase self-assembly of n-octylphosphonic acid (C8PA) monolayer in vacuum that leads to a well chemisorbed monolayer of C8PA. When such a monolayer is attached to ~ 9-nm thick aluminium oxide to form an ultra-thin dielectric implemented in low-voltage organic thin-film transistors based on pentacene, the transistor performance exhibits measurable changes upon alteration of the structure of the C8PA monolayer.