Nanostructural depth-profile and field-effect properties of poly(alkoxyphenylene-thienylene) Langmuir–Schäfer thin-films

The correlations between morphological features and field-effect properties of poly(alkoxyphenylene-thiophene) thin Langmuir–Schäfer filmdeposited on differently terminated gate dielectric surfaces, namely bare and methyl functionalized thermal silicon dioxide (t-SiO2), have beensystematically studied. The film morphology has been investigated at different film thickness by Scanning Force Microscopy. Films thicker than afew layers show comparable morphology on both dielectric surfaces while differences are seen for the ultra-thin polymer deposit in closeproximity to the substrate. Such deposit is notably more heterogeneous on bare t-SiO2, while a more compact and uniform nanogranular structureis observed on the silylated t-SiO2. As to the field-effect properties, the methyl-terminated gate dielectric surface leads to a two order of magnitudemobility enhancement along with a field-effect thickness independent conductance.