Theoretical study of electronic and transport properties of PPy-Pt(111) and PPy-C(111):H interfaces.

We present a first-principles study of promising hybrid organic-inorganic interface systems consisting of a polypyrrole (PPy) chain sandwiched between metallic Pt(111) or hydrogen-terminated diamond C(111):H electrodes. We combine ab initio density-functional-theory total energy calculations, Green's function approach and the complex band-structure method in order to determine electronic and transport properties of those organic-semiconductor/metal (semiconductor) interfaces. We analyze one- and multi-bond nanocontact formation including structural modification (H desorption) as well as PPy length dependence. For selected ground state configurations of the considered interface systems we study their energetics and structural properties. Through the analysis of the local density of states, in particular isosurfaces of the charge density, the mechanism of the charge transfer and the charge neutrality levels are determined. The voltage dependence of the electrical conductance and the I-V characteristics are compared to the transport properties based on the complex band-structure method. The obtained results support recent experiments, where PPy nanowires are formed via electrochemical synthesis and placed between platinum or diamond microelectrodes.