Role of interfaces on the direct tunneling and the inelastic tunneling behaviors through metal/alkylsilane/silicon junctions

Abstract

We studied the influence of the end group of the alkylsilane molecule used in Self Assembled Monolayer (SAM) in Silicon/SAM/Metal junctions. By Inelastic Electron Tunneling spectroscopy (IETS), we showed the formation of a covalent bond between the molecules and the gold electrode in the case of a thiol terminated alkylsilane. By electrical characterizations, we demonstrated that the thiol group at the interface avoids diffusion of gold into the molecule even for a 3 carbons chain. For this short molecule, we observed pure tunnel conduction with barrier height at the monolayer/Si and monolayer/Au interfaces found to be respectively 2.14 and 2.56 eV. These values were obtained using Simmons equation with an effective mass parameter m* = 0.16m e (m e = mass of the electron).This extends the demonstration of the excellent tunnel dielectric behavior of these organic monolayers down to 3 carbon atoms with a thiol/Au bond at the interface.

Molecule-induced interface states dominate charge transport in Si–alkyl–metal junctions

“…All alkanethiol vibrational features observed previously in Aualkanethiol-Au junctions [5] also appear in the IET spectra of the SMM junctions. The observed peaks are also in agreement with those reported by Vuillaume and co-workers for metalalkanethiol-siliconoxide/silicon junctions [23,24]. The relative intensity of the different alkyl vibrational peaks are however quite different from our earlier Au-alkanethiol-Au results (e.g.…”

Fabrication of Reproducible, Integration‐Compatible Hybrid Molecular/Si Electronics

“…The deposited top contact can also interact with, and chemically alter the monolayer, in addition to the above‐considered diffusion through the molecular layer. Such interaction was actually exploited to prevent diffusion in certain cases . However, for molecule‐Si hybrids the molecular dipole plays a key role, and, therefore, we wish to preserve the molecules as intact as possible.…”

“…There are some reports of reliable direct metal evaporation, but their success depends critically on specific terminal groups, such as thiol for Au, or carboxylic acid for Al . In a different approach, Hacker and coworkers observed that evaporated Au over an alkyl monolayer on Si leads to short junctions while evaporated Ag preserves the molecular tunneling barrier.…”

Molecular electronics based on self-assembled monolayers

“…Finally, these tunnel junctions are also good prototypal devices to study more detailed phenomena such as: electron -molecular vibration coupling using inelastic electron tunnel spectroscopy (IETS) (Kushmerick et al, 2004, Wang et al, 2004, Petit et al, 2005, Aswal et al, 2006, Beebe et al, 2007, Long et al, 2006, current-induced local heating in a molecular junction (Huang et al, 2006), dynamical charge fluctuations using noise measurements (Clement et al, 2007) and spin-polarized transport (Petta et al, 2004, Wang andRichter, 2006). Beyond the first results, more of such experiments are now required to achieve a good agreement between a variety of different results, as well as with theoretical predictions.…”