Metal-free molecular junctions on ITO via amino-silane binding-towards optoelectronic molecular junctions

• Published in: Nanotechnology Vol. 24; no. 45; p. 455204
• Main Authors: Sergani, S, Furmansky, Y, Visoly-Fisher, I
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 15.11.2013; Institute of Physics
• Subjects: Applied sciences; Binding; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronics; Exact sciences and technology; Materials science; Methods of nanofabrication; Molecular electronics, nanoelectronics; Physics; Self-assembly; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Surface and interface electron states; Self-assembled layer; Optoelectronics; Thiol; Transport properties; Optoelectronic properties; Molecular structure; Photoinduced effect; Polymer; Indium oxide; Nanoelectronics; Quenching; Molecular electronics; Plasmon; Tin oxide; Molecular junction; Spatial resolution; Silane; Excited state
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/24/45/455204

Light control over currents in molecular junctions is desirable as a non-contact input with high spectral and spatial resolution provided by the photonic input and the molecular electronics element, respectively. Expanding the study of molecular junctions to non-metallic transparent substrates, such as indium tin oxide (ITO), is vital for the observation of molecular optoelectronic effects. Non-metallic electrodes are expected to decrease the probability of quenching of molecular photo-excited states, light-induced plasmonic effects, or significant electrode expansion under visible light. We have developed micron-sized, metal free, optically addressable ITO molecular junctions with a conductive polymer serving as the counter-electrode. The electrical transport was shown to be dominated by the nature of the self-assembled monolayer (SAM). The use of amino-silane (APTMS) as the chemical binding scheme to ITO was found to be significant in determining the transport properties of the junctions. APTMS allows high junction yields and the formation of dense molecular layers preventing electrical short. However, polar amino-silane binding to the ITO significantly decreased the conductance compared to thiol-bound SAMs, and caused tilted geometry and disorder in the molecular layer. As the effect of the molecular structure on transport properties is clearly observed in our junctions, such metal-free junctions are suitable for characterizing the optoelectronic properties of molecular junctions.