Self-organized C70/C60 heterojunction nanowire arrays on Si(110) for Si- based molecular negative differential resistance nanodevices

Periodic organic heterojunction nanowires on Si(1 1 0) were successfully constructed through the self-organization of C-70 molecules on the nanotemplate of parallel C-60-triplet nanowire array on Si(1 1 0) at room tem-perature. Scanning tunneling microscopy images show that the preferential adsorption of three C-70 molecules (i.e., C-70 triplet) at the bridge site of two C-60 triplets makes C-70-triplet nanowires grow epitaxially along original C-60-triplet nanowires, leading to the formation of parallel-aligned C-70-triplet/C-60-triplet heterojunction nanowires over a large area on Si(1 1 0). Scanning tunneling spectroscopy results show that these C-70/C-60 hetero-junction nanowires on Si(1 1 0) exhibit obvious negative differential resistance (NDR) at room temperature. Using first-principles calculations based on density functional theory and non-equilibrium Green's function formalism, we suggest that the origin of observed NDR of C-70/C-60 heterojunction nanowires on Si(1 1 0) is mainly attributed to the relatively weak interaction between C-70 molecules and Si(1 1 0) via the spacers of C-60 molecules. This controlled organization of mesoscopically-ordered organic heterojunction nanowire array on Si(1 1 0) provides a feasible way for molecular engineering of one-dimensional functional Si-based molecular hierarchical nanoarchitectures by deposition of tailored molecules on parallel C-60 molecular nanowire arrays on Si(1 1 0), realizing the large-scale integration of desired molecular functionalities into Si-based organic nanodevices for applications in nanoelectronics, photovoltaics, and spintronics.