Electrostatic Fermi level tuning in large-scale self-assembled monolayers of oligo(phenylene-ethynylene) derivatives.

Autor: Wang X; Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.; School of Information Science and Technology, Dalian Maritime University, Dalian, China., Ismael A; Physics Department, Lancaster University, Lancaster, LA1 4YB, UK. c.lambert@lancaster.ac.uk.; Department of Physics, College of Education for Pure Science, Tikrit University, Tikrit, Iraq., Ning S; Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK., Althobaiti H; Physics Department, Lancaster University, Lancaster, LA1 4YB, UK. c.lambert@lancaster.ac.uk.; Department of Physics, College of Science, Taif-University, Taif, Saudi Arabia., Al-Jobory A; Physics Department, Lancaster University, Lancaster, LA1 4YB, UK. c.lambert@lancaster.ac.uk.; Department of Physics, College of Science, University of Anbar, Anbar, Iraq., Girovsky J; Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK., Astier HPAG; Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK., O'Driscoll LJ; Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, DH1 3LE, UK., Bryce MR; Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, DH1 3LE, UK., Lambert CJ; Physics Department, Lancaster University, Lancaster, LA1 4YB, UK. c.lambert@lancaster.ac.uk., Ford CJB; Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
Jazyk: angličtina
Zdroj: Nanoscale horizons [Nanoscale Horiz] 2022 Sep 26; Vol. 7 (10), pp. 1201-1209. Date of Electronic Publication: 2022 Sep 26.
DOI: 10.1039/d2nh00241h
Abstrakt: Understanding and controlling the orbital alignment of molecules placed between electrodes is essential in the design of practically-applicable molecular and nanoscale electronic devices. The orbital alignment is highly determined by the molecule-electrode interface. Dependence of orbital alignment on the molecular anchor group for single molecular junctions has been intensively studied; however, when scaling-up single molecules to large parallel molecular arrays (like self-assembled monolayers (SAMs)), two challenges need to be addressed: 1. Most desired anchor groups do not form high quality SAMs. 2. It is much harder to tune the frontier molecular orbitals via a gate voltage in SAM junctions than in single molecular junctions. In this work, we studied the effect of the molecule-electrode interface in SAMs with a micro-pore device, using a recently developed tetrapodal anchor to overcome challenge 1, and the combination of a single layered graphene top electrode with an ionic liquid gate to solve challenge 2. The zero-bias orbital alignment of different molecules was signalled by a shift in conductance minimum vs. gate voltage for molecules with different anchoring groups. Molecules with the same backbone, but a different molecule-electrode interface, were shown experimentally to have conductances that differ by a factor of 5 near zero bias. Theoretical calculations using density functional theory support the trends observed in the experimental data. This work sheds light on how to control electron transport within the HOMO-LUMO energy gap in molecular junctions and will be applicable in scaling up molecular electronic systems for future device applications.
Databáze: MEDLINE