Vibronic states in single molecules: C60 and C70 on ultrathin Al2O3 films

Abstract

Vibronic states are observed in single C(60) and C(70) molecules by scanning tunneling microscopy. When single fullerene molecules are adsorbed on a thin layer of Al(2)O(3) grown on a NiAl(110) substrate, equally spaced features are observed in the differential conductance (dI/dV), which are clearly resolved in d(2)I/dV(2) spectra. These features are attributed to the vibronic states of the molecule. The vibronic progressions are sensitive to the molecular orientations and can have different spacings in different electronic bands of the same molecule. For C(60,) these vibronic states are associated with the intramolecular A(g) and H(g) vibrational modes. Vibronic states are not resolved in molecules adsorbed on the metal surface. However, inelastic electron tunneling spectroscopy exhibits a vibrational mode at 64 meV for C(60) and 61 meV for C(70) adsorbed on NiAl(110).

Numerically exact, time-dependent treatment of vibrationally coupled electron transport in single-molecule junctions

“…The signature of nuclear motion has been observed in conduction measurements of a variety of molecular junctions, 11,14,16,18,19,[25][26][27][35][36][37][38][39][40][41][42][43][44][45][46] e.g., H 2 between platinum electrodes, 14 C 60 molecules between gold electrodes, 11 and copper phthalocyanine 19 on aluminum oxide film. Vibrational signatures of molecular bridges have also been observed in inelastic electron tunneling spectroscopy.…”

“…[1][2][3][4][5][6][7][8][9][10] Employing different experimental techniques, including electromigration or mechanically controllable break junctions or scanning tunneling microscopy, 1,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] the conductance properties of nanoscale molecular junctions have been investigated. The observed current-voltage characteristics typically exhibit a nonlinear behavior with resonance structures at larger bias voltages associated with the discrete energy levels of the molecular bridge.…”

Green Function Techniques in the Treatment of Quantum Transport at the Molecular Scale

“…With their help, a plethora of interesting phenomena like rectification [18], negative differential conductance [9,35], Coulomb blockade [23,10,11,15,16,21], Kondo effect [11,12], vibrational effects [10,25,13,14,16,31,32,33,35,36,21], and nanoscale memory effects [34,39,40,42,44], among others, have been demonstrated.…”

Numerically exact, time-dependent study of correlated electron transport in model molecular junctions

“…[1][2][3][4][5][6][7][8][9][10] Single molecule junctions, consisting of single molecules that are chemically bound to metal electrodes, are well-suited systems to study nonequilibrium transport phenomena at the nanoscale and are also of interest for potential applications in the field of molecular electronics. Recent developments in experimental techniques, such as electromigration, mechanically controllable break junctions, or scanning tunneling microscopy, 1, [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] have made it possible to study transport properties of molecular junctions. The rich experimental observations, e.g., Coulomb blockade, 13 Kondo effect, 29 negative differential resistance, 26,30,31 switching and hysteresis, [32][33][34] have stimulated many theoretical developments for understanding quantum transport at the molecular scale.…”