| AVS 65th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology Division | Thursday Sessions |
| Session NS+2D+AS+MN+PC-ThA |
| Session: | SPM – Probing Electronic and Transport Properties |
| Presenter: | Sidney Cohen, Weizmann Institute of Science, Israel |
| Authors: | S.R. Cohen, Weizmann Institute of Science, Israel B. Kayser, Weizmann Institute of Science, Israel C. Gua, Weizmann Institute of Science, Israel M. Sheves, Weizmann Institute of Science, Israel I. Pecht, Weizmann Institute of Science, Israel D. Cahen, Weizmann Institute of Science, Israel |
| Correspondent: | Click to Email |
Electron transport studies provide an excellent platform to deduce electronic structure in molecular electronics studies, enabling control and understanding of the pathways and mechanisms involved. Due to their complexity, proteins are used only infrequently in this context, despite convenient properties such as selective binding, self-assembly, light sensitivity, and the possibility to (bio) chemically tailor properties . Here, we study electron transport in monolayer films of Azurin, using a 3-electrode configuration with a novel side-gate. The source and drain are gold substrate and conductive atomic force microscope (C-AFM) probe, respectively. The measuring devices were prepared in a two-step electron beam lithography process, whereby interdigitated drain and gate electrodes with separation of 80 nanometers are patterned from macroscopic electrodes, the latter formed optically on a silicon oxide substrate. The gold electrodes are patterned with the gate elevated by 20 nm for improved coupling with the drain. After deposition of the Azurin monolayer on this structure, the carrier chip was wire-bonded for insertion into the AFM. Azurin was incorporated in the device both as copper-containing holo-Azurin, and as apo-Azurin with the Cu ion removed. Stability of source-drain vs. Vsource-drain curves, as well as gate-drain leakage were monitored for validity. Isource- drain vs. Vsource-drain curves were acquired at different gate voltages, and Isource- drain at 0 Vsource-drain was measured while sweeping Vgate in both polarities. Asymmetry of current onset for opposing gate biases points to a low-lying LUMO transport level for holo-Azurin. For apo-Azurin this level is shifted to higher values and hence inaccessible. Semi-quantitative location of the tail of this LUMO, as well as value of gate coupling were estimated by changing the work function of the drain electrode, i.e. C-AFM probe, from Pt (φ=-5.3 eV) to Au (φ= -4.9 eV). The observations can be rationalized by considering previous electrochemical and theoretical studies.