Importance of Oxides in Carbon/Molecule/Metal Molecular Junctions with Titanium and Copper Top Contacts
نویسندگان
چکیده
Carbon/molecule/metal molecular junctions were fabricated by metal deposition of titanium or copper on monolayers of nitroazobenzene ~NAB!, biphenyl, and nitrobiphenyl ~NBP!, and multilayers of NAB and NBP covalently bonded to an sp2 carbon substrate. The electronic behavior of Ti junctions was extremely dependent on residual gas pressure during E-beam deposition, due to the formation of a disordered Ti oxyhydroxide deposit. The junction resistance decreased with decreasing residual gas pressure, and the hysteresis and rectification observed previously for relatively high deposition pressure was absent for pressures below 5 3 10−7 Torr. Deletion of the molecular layer resulted in low-resistance junctions for both high and low deposition pressures. Replacement of the Ti with Al with otherwise identical deposition conditions resulted in insulating junctions with much higher resistance and no rectification. Ti junctions made at low residual gas pressure had resistances and current/voltage characteristics similar to those of junctions with Cu top contacts, with the latter exhibiting high yield and good reproducibility. The current/ voltage characteristics of both the Ti and Cu junctions fabricated with low residual gas pressure were nonlinear and showed a strong dependence on the molecular layer thickness. The hysteresis and rectification previously observed for junctions fabricated at relatively high residual gas pressure depend on the combination of the NAB layer and the semiconducting TiOx film, with the TiOx layer conductivity depending strongly on formation conditions. Rectification and hysteresis in NAB/TiOx junctions may result from either redox reactions of the NAB and TiOx layers, or from electron injection into the conduction band of Ti oxide. © 2005 The Electrochemical Society. @DOI: 10.1149/1.1888369# All rights reserved.
منابع مشابه
Electron transport and redox reactions in carbon-based molecular electronic junctions.
A unique molecular junction design is described, consisting of a molecular mono- or multilayer oriented between a conducting carbon substrate and a metallic top contact. The sp2 hybridized graphitic carbon substrate (pyrolyzed photoresist film, PPF) is flat on the scale of the molecular dimensions, and the molecular layer is bonded to the substrate via diazonium ion reduction to yield a strong,...
متن کاملMolecular electronics using diazonium-derived adlayers on carbon with Cu top contacts: critical analysis of metal oxides and filaments.
Evaporation of Cu metal onto thin (less than 5 nm) molecular layers bonded to conductive carbon substrates results in electronic junctions with an ensemble of molecules sandwiched between two conductors. The resulting devices have previously been characterized through analysis of current density-voltage (j-V) curves for several different molecular layers and as a function of layer thickness. Th...
متن کاملAll-carbon molecular tunnel junctions.
This Article explores the idea of using nonmetallic contacts for molecular electronics. Metal-free, all-carbon molecular electronic junctions were fabricated by orienting a layer of organic molecules between two carbon conductors with high yield (>90%) and good reproducibility (rsd of current density at 0.5 V <30%). These all-carbon devices exhibit current density-voltage (J-V) behavior simila...
متن کاملElectron-beam evaporated silicon as a top contact for molecular electronic device fabrication.
This paper discusses the electronic properties of molecular devices made using covalently bonded molecular layers on carbon surfaces with evaporated silicon top contacts. The Cu "top contact" of previously reported carbon/molecule/Cu devices was replaced with e-beam deposited Si in order to avoid Cu oxidation or electromigration, and provide further insight into electron transport mechanisms. T...
متن کاملEffects of electronic coupling and electrostatic potential on charge transport in carbon-based molecular electronic junctions
Molecular junctions consisting of 2-20 nm thick layers of organic oligomers oriented between a conducting carbon substrate and a carbon/gold top contact have proven to be reproducible and reliable, and will soon enter commercial production in audio processing circuits. The covalent, conjugated bond between one or both sp(2)-hybridized carbon contacts and an aromatic molecular layer is distinct ...
متن کامل