Graphene shows great
promise not only as a highly conductive flexible
and transparent electrode for fabricating novel device architectures
but also as an ideal synthesis platform for studying fundamental growth
mechanisms of various materials. In particular, directly depositing
metal phthalocyanines (MPc’s) on graphene is viewed as a compelling
approach to improve the performance of organic photovoltaics and light-emitting
diodes. In this work, we systematically investigate the ZnPc physical
vapor deposition (PVD) on graphene either as-grown on Cu or as-transferred
on various substrates including Si(100), C-plane sapphire, SiO2/Si, and h-BN. To better understand the effect of the substrate
on the ZnPc structure and morphology, we also compare the ZnPc growth
on highly crystalline single- and multilayer graphene. The experiments
show that, for identical deposition conditions, ZnPc exhibits various
morphologies such as high-aspect-ratio nanowires or a continuous film
when changing the substrate supporting graphene. ZnPc morphology is
also found to transition from a thin film to a nanowire structure
when increasing the number of graphene layers. Our observations suggest
that substrate-induced changes in graphene affect the adsorption,
surface diffusion, and arrangement of ZnPc molecules. This study provides
clear guidelines to control MPc crystallinity, morphology, and molecular
orientations which drastically influence the (opto)electronic properties.