Tuning surface d bands with bimetallic electrodes to facilitate electron transport across molecular junctions
In many years, the Ministry of Science and Technology has been encouraging the scientific research. This research plan is under the long-term support of the Ministry of Science and Technology, Prof. Chun-hsien Chen and Prof. I-Wen Peter Chen have been created to turn surface d bands with bimetallic electrodes to facilitate electron transport across molecular junctions. This outstanding fundamental research result was published in the top journal ⟪ Nature Materials ⟫ in 2021.
Understanding chemical bonding and conductivity at the electrode–molecule interface is key for the operation of single-molecule junctions. Here we apply the d-band theory that describes interfacial interactions between adsorbates and transition metal surfaces to study electron transport across these devices. We realized bimetallic Au electrodes modified with a monoatomic Ag adlayer to connect α,ω-alkanoic acids (HO2C(CH2)nCO2H). The force required to break the molecule–electrode binding and the contact conductance Gn=0 are 1.1 nN and 0.29 G0 (the conductance quantum, 1 G0 = 2e2/h ≈ 77.5 μS), which makes these junctions, respectively, 1.3–1.8 times stronger and 40–60-fold more conductive than junctions with bare Au or Ag electrodes. A similar performance was found for Au electrodes modified by Cu monolayers. By integrating the Newns–Anderson model with the Hammer–Nørskov d-band model, we explain how the surface d bands strengthen the adsorption and promote interfacial electron transport, which provides an alternative avenue for the optimization of molecular electronic devices.
Establishing a solid base of fundamental research is crucial for the future advance of the high-tech industry in Taiwan. The success of this research project also represents a milestone for in the research of fundamental science in Taiwan and meets the objectives of the program.
Dr. Chun-hsien Chen, Professor, Department of Chemistry, National Taiwan University
Tel: (02) 02-3366-4191