STM and DFT Investigations of Isolated Porphyrin on a Silicon‐Based Semiconductor at Room Temperature

Abstract

Metalloporphyrins represent a class of flexible molecules with a nearly square planar core conformation and a two dimensional conjugated p-electron delocalization. Due to their interesting physicochemical properties, metalloporphyrins adsorbed on a surface can be used in many technological applications such as molecular electronics, light-harvesting arrays for solar energy generation, catalysts, sensors, etc. The fine determination of the conformation and arrangement of adsorbed molecules on a surface are key points, since they are strongly related to the physical and chemical properties of the final organic–inorganic interfaces. They are changed by the subtle balance of internal deformation and substrate–molecule interactions, leading to a conformational adaptation of the molecule on the substrate lattice. These features are even more relevant in semiconductors than in metals because the moleculesemiconductor interactions are usually greater than molecule– metal interactions. Although scanning tunneling microscopy (STM) is a remarkable tool to investigate individual adsorbed molecules on semiconductors, experimental STM images of metalloporphyrins were achieved only on metals and only an unique very recent article investigates theoretically the adsorption of a metalloporphyrin on a Si(111)-H surface. Herein, we report the first experimental investigation at room temperature of the adsorption of Cu-5,10,15,20-tetrakis(3,5-di-tert-butylphenyl) porphyrin (Cu-TBPP) as a model of metalloporphyrin on a passivated silicon based surface (Si(111)-B) using STM and by theoretical calculations in order to fully understand the conformational adaptation of the Cu-TBPP on a Si(111)-B surface.