Tunneling spectroscopy of fullerene/Ge multilayer systems

Inelastic Electron Tunneling Spectroscopy

“…Nolen and Ruggiero 32 have measured the vibrational IETS of C 60 and C 70 using a multilayer barrier of C n interleaved with Ge. These barriers are much thicker than any previously measured by IETS and therefore have surprisingly low barrier heights.…”

“…Thus, all but 9 of the 46 fundamental bands could be assigned through a combination of all four data sets. Recently, Nolen and Ruggiero 32 have used an interesting composite barrier design to make tunnel junctions that provided IETS wherein 26 of the silent modes of C 60 were identified. Thus, all but 6 of the 46 fundamentals have been directly observed through the concerted use of IR, Raman, INS, and IETS.…”

“…We note first that a long standing concern about the application of IETS to large biomolecules (such as hemoglobin) is that they are so thick that tunneling is only effective at the periphery. The success with which Nolen and Ruggiero 32 were able to measure the relatively large C 70 via a laminated barrier structure suggests that there yet may be hope for IETS studies of moderately thick biomolecules.…”

Spatially Dependent Inelastic Tunneling in a Single Metallofullerene

“…Molecular components, however, differ from conventional electronic elements in the degree to which mechanical degrees of freedom affect electrical conductivity [3,4]. Understanding this behavior in molecular systems is complicated by difficulties in identifying conductanceaffecting molecular modes and by discrepancies between single molecule and ensemble measurements [5,6]. These discrepancies are not well understood, but have been speculated to arise from molecular electron-phonon coupling selection rules [7,8] and effects due to phonon dynamics, such as the orientation of phonon displacements with respect to tunneling electrodes [9].…”

“…Though the molecular phonon modes and electronic wave function extend over the whole molecule, we show that the expected coupling of the dominant cage vibrational mode to the electronic molecular wave function is spatially localized, leading to highly localized IESTS signals. This suggests that differences between molecular layer and single molecule inelastic tunneling measurements might arise from the limited sampling of molecular locations in single molecule experiments [5,6].…”