Understanding and Controlling Electronic Transport via Proteins: Nanoscale Electrode Architecture-enabled Energy Level Alignment

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In this project we want to answer the question "(how) can gating control the efficiency and the mech-anism of electron transport across proteins?". Much knowledge and understanding has accumulated on charge transfer processes in several proteins. There is also growing interest in charge transport through proteins in solid state-type junctions. Still, there are very central open questions concerning what appears to be remarkably efficient charge transport and its temperature-(in)dependence, ques-tions that impact directly the issue of what is/are the underlying transport mechanism(s). As known from other areas of electronics, use of a 3rd electrode in a solid-state architecture can allow con-trolled electrostatic 'gating' of charge transport (as in field-effect transistors). Finding ways to repro-ducibly add gating will be a huge step towards answering these open questions and unraveling elec-tron transport across proteins. With a gate the protein molecular electronic energy level distribution may be shifted w.r.t the leads Fermi levels, for correlation with the corresponding transport process-es. We intend to achieve the abovestated goal to allow tackling the fundamental issue of transport mechanisms technically by realizing different architectures of highly doped silicon contacts which are separated by a few up to ~ 10 nm, only (nanogap electrodes), and which feature a gate electrode in close proximity. We will use selected, suitable protein systems and after characterizing these thoroughly on planar surfaces such as those of same material as the electrodes, the nanogaps shall be specifically functionalized with these proteins. Subsequently, electrical transport measurements will be carried out on these nanogap devices as function of gate voltage, at varying temperatures and where applicable, as function of illumination. Additional, advanced characterization methods such as inelastic electron tunneling spectroscopy will complement the fundamental charge transport stud-ies. We will analyze and model our electrical data within the framework of existing and, as they be-come available, possibly new, theoretical models of charge transport through proteins contacted by solid-state electrodes. We expect that our work will provide muchneeded data, required to under-stand the complex charge transport scenarios in proteins, and eventually will become relevant for future applications in the field of bioelectronics including sensing, energy conversion and information storage.