Grazing Incidence Small-Angle X-ray Scattering Analysis of Initial Growth of Planar Organic Molecules Affected by Substrate Surface Energy

Disc-type nano grains of copper(II) phthalocyanine (CuPc) were observed in an ultrathin CuPc layer (5 nm) evaporated on a hydrophilic Si surface showing the structure factor in grazing incidence small-angle X-ray scattering measurement. The disk type grains consisted of a crystalline part and a noncrystalline part. The disk type grains were smaller in the case of evaporation on an octadecyltrichlorosilane (ODTS) treated hydrophobic Si surface, which showed lower crystallinity with random distribution. Despite regularly distributed CuPc grains, the mobility was lower in a FET device fabricated on a hydrophilic surface than on an ODTS Si surface due to the lower average density of the molecules relating to porous molecular packing between nanograins on a hydrophilic surface.