Inelastic electron tunneling junctions

Figure 1. Schematic representation of an inelastic electron tunnel junction.

Another technique that has proved useful in establishing chemical bonding of coupling agents at interfaces is inelastic electron tunneling spectroscopy (ITES). For example. Van Velzen [16] examined 3-(trimethoxysilyl)propanethiol by this technique. Approximately monolayer quantities of this silane were adsorbed on the barrier oxide of an aluminum-aluminum oxide-metal tunneling junction two metals were investigated, lead and silver. It was concluded that the silane is... 

Section 5 is on one particular molecule, p-benzene dithiol. This is one of the most commonly studied molecules in molecular electronic transport junctions [7] (although it is also one of the most problematic). Section 6 discusses a separate measurement, inelastic electron tunneling spectroscopy [8, 9] (IETS). This can be quite accurate because it can be done on single molecules at low temperatures. It occurs because of small perturbations on the coherent transport, but it can be very indicative of such issues as the geometrical arrangement in the molecular transport junction, and pathways for electron transport through the molecular structure. 

Troisi A, Ratner MA (2005) Modeling the inelastic electron tunneling spectra of molecular wire junctions. Phys Rev B 72(3) 033408... 

Galperin M, Ratner MA, Nitzan A (2004) Inelastic electron tunneling spectroscopy in molecular junctions peaks and dips. J Chem Phys 121 (23) 11965—11979... 

Troisi A, Ratner MA (2006) Molecular transport junctions propensity rules for inelastic electron tunneling spectra. Nano Lett 6(8) 1784-1788... 

Apart from the more conventional transport measurements of molecular junctions at constant bias voltage, alkane(di)thiols-based molecular junctions were also characterized by transition voltage spectroscopy [258, 259], AC voltage modulation [260], and inelastic electron tunneling spectroscopies [261],... 

Arroyo CR, Frederiksen T, Rubio-Bollinger G, Velez M, Amau A, Sanchez-Portal D, Agrai t N (2010) Characterization of single-molecule pentanedithiol junctions by inelastic electron tunneling spectroscopy and first-principles calculations. Phys Rev B 81 075405/1-075405/5... 

Ando Y, Murai J, Miyazaki T (1999) Analysis of the interface in ferromagnet/insulator junctions by inelastic-electron-tunneling-spectroscopy. J Magn Magn Mater 198-199 161-163... 

Yu L, Zangmeister CD, Kushmerick JG (2007) Origin of discrepancies in inelastic electron tunneling spectra of molecular junctions. Phys Rev Lett 98 206803-206804... 

Inelastic electron tunneling spectroscopy (lETS) takes advantage of the general applicability of vibrational spectroscopy by measuring the vibrational spectrum of molecules adsorbed on the insulation of a metal-insulator-metal junction (Figure 1). 

Wang W, Richter CA (2006) Spin-polarized inelastic electron tunneling spectroscopy of a molecular magnetic tunnel junction. Appl Phys Lett 89 153105... 

Near one metal electrode the potential for a dipole oriented normal to the interface tends to add with that of its image in the metal electrode. The potentials of the dipole and its image tend to cancel for a dipole oriented parallel to the interface. The addition or cancellation of the dipole potential with its image makes it more probable for an inelastic transition to occur for a dipole oriented normal to the interface. Near the center of a tunneling junction, however, the reverse is true for two reasons. 1) The cancellation of potentials for the dipole oriented parallel is least important at the center. 2) The inelastic transition matrix element involves an integration over the barrier volume of the interaction potential times some nearly spatially homogeneous electronic wavefunction terms. If the dipole is oriented normal to the interfaces and located in the center of the barrier, the potential is an odd function in z ( if z defines the normal to the interfaces ), and integrates to... 

Thus far the discussion has centered on elastic tunneling, but consideration of inelastic processes may offer additional analytical opportunities. An energy scale of the relevant phenomena is presented in Table 2. Inelastic tunneling was first observed in metal-oxide-metal junctions. It was immediately developed as a technique for photon-free vibrational spectroscopy (lETS) where the tunneling electrons dissipate energy by coupling to vibra-... 

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