Intrinsic Charge Trapping Observed as Surface Potential Variations in diF-TES-ADT Films

Spatial variations in surface potential are measured with Kelvin probe force microscopy for thin films of 2,8-difluoro-5,11-bis­(triethyl­silyl­ethynyl)­anthra­dithio­phenes (diF-TES-ADT) grown on SiO₂ and silane-treated SiO₂ substrates by organic molecular beam deposition. The variations are observed both between and within grains of the polycrystalline organic film and are quantitatively different than electrostatic variations on the substrate surfaces. The skewness of surface potential distributions is larger on SiO₂ than on HMDS-treated substrates. This observation is attributed to the impact of substrate functionalization on minimizing intrinsic crystallographic defects in the organic film that can trap charge.