Long range charge transport in Molecular Electronic devices

点击翻译按钮获取中文摘要

The field of molecular electronics (ME) seeks to enhance electronic functions of conventional microelectronic devices by incorporating molecules into electronic circuits to improve performance, lower costs, reduce power demands and provide novel electronic functions. Our group was the first to develop a reliable, reproducible molecular junction with sufficient lifetime (~ years) and temperature tolerance (-260 to +300 °C) for practical applications. This junction enabled an audio processing function not possible with silicon, and a prototype developed in 2014 is currently being evaluated for commercialization in an audio accessory market exceeding $2B/year worldwide. Of particular importance in such devices are the electron transport mechanisms over distances in the 1-25 nm range, which differ fundamentally from the transport in either conventional semiconductors or in the thicker films (>50 nm) in widely studied "organic" electronics. We plan to explore novel transport mechanisms that exploit molecular orbitals for charge transport, with the ultimate objective of rationally designing novel electronic behaviours using variations in molecular structure. We have reported initial results on an ionization mechanism strongly dependent on molecular structure and operative over 5-20 nm, distances too great for quantum mechanical tunneling. A transport distance range of 1-25 nm not only avoids the pitfalls of "organic electronics" but also enables "ballistic" transport, which can enable very high frequency operation (>1000 GHz). We will use the robust molecular junction structure developed over the past decade to pursue three related fundamental subprojects on how molecular structure affects electronic behaviour:***Project 1: Structural Control of Transport. Thiophene derivatives with similar structures but varying energy levels will be investigated in the distance range beyond tunneling (i.e., 5-20 nm), where we have observed strong effects of orbital energies. We will investigate the effects of variations in orbital energies to resonant transport, field ionization, and ballistic transport mechanisms.***Project 2: Bi-layer and Tri-layer Junctions. Differences in orbital energies of adjacent molecular layers are expected to cause rectification and possibly resonance between the contacts and molecular orbitals. We will study the effects of orbital energies on transport to help formulate the "design rules" of molecular electronic behaviour.***Project 3: Optical Monitoring of Working Molecular Devices. In addition to verifying device structures via spectroscopy, we will investigate device photocurrents and light emission as probes of internal energy levels and ballistic transport.***These projects have the potential to lead to an entire new class of microelectronics based on molecular junctions with valuable functions and behaviours distinct from those of silicon.**