Impact of scaling of dielectric thickness on mobility in top-contact pentacene organic thin film transistors

The effect of scaling of poly(methylmethacrylate) (PMMA) and cross-linkable poly(4-vinylphenol) (PVP) polymer dielectric thickness on field effect mobility in top contact pentance organic thin film transistors was investigated. Mobility at a constant gate voltage improved significantly with reduction in thickness of both dielectrics. Analysis at a constant gate electric field or identical induced accumulation charge revealed that only a part of the improvement occurs due to simple scaling of dielectric thickness, and the remaining is due to improvement in interface quality. Atomic force microscopic analysis of the dielectric surface revealed that dielectric roughness reduced with reduction in dielectric thickness. A comparison of the two dielectrics also indicates that band mobility is significantly higher in pentacene/PMMA as compared to pentacene/PVP dielectric. (C) 2012 American Institute of Physics. [doi:10.1063/1.3681809]