Halide Anchors for Single-Cluster Electronics

Due to their unique electronic structure,well-defined metal clusters at the atomic level are promising materials for single-cluster electronics.However,coupling between the electrode and the cluster remains challenging mainly due to the coverage of bulky ligands on the noble clusters.Using the scanning tunneling microscopy break junction(STM-BJ)technique,we have developed a“direct contact”approach to fabrication and investigation of the charge transport through single-cluster junctions of AgCu bimetallic metal clusterswith different halide anchors.Wefound that the electrodes could make contact directly with the surface halides of the single-cluster junctions and experience different contact resistance from different halogen atoms.Experiments and calculations reveal that the halide anchors provided efficient coupling between the cluster and the electrode,and the enhanced coupling with various halide anchors promoted electron transport and improved transmission probability.Our work offers a“direct contact”strategy for interface design between clusters of noble metals and electrodes,an essential step in progress toward single-cluster electronics.

Sub-nanometer supramolecular rectifier based on the symmetric building block with destructive σ-interference

Molecular rectifier, as a basic function of molecular electronic devices, has attracted extensive attention for the opportunity in constructing sub-nanometer electronic devices. However, tunneling leakage current has a significant contribution as electronic devices shrink in size, which leads to a challenge in fabricating molecular rectifiers at the sub-nanometer scale. Here, we experimentally demonstrate a sub-nanometer molecular rectifier based on the supramolecular junction assembled between water and 1,4-diazabicyclo[2.2.2]octane (DABCO) molecule. The charge transport through DABCO and corresponding supramolecular junctions exhibits destructive σ-interference, ensuring a sharp conductance variation for transmission modulation. The supramolecular interaction between DABCO and water readily introduces the asymmetric electrode-molecule interaction, which combines with the destructive σ-interference to support the sub-nanometer rectification.

Highly insulating alkane rings with destructive σ-interference

Destructive quantum interference(DQI)provides a unique approach to controlling the leakage current in the OFF state of molecular devices.However,the DQI in π-conjugated molecular building blocks cannot exhibit ultralow conductance due to the existence of covalently bonded σ-transport channels.Thus,suppressing the σ-contribution via σ-DQI is essential for the fabrication of molecular junctions with high insulation and effective modulation of conductance in single-molecule junctions.Here,we demonstrate the existence of σ-DQI even in a simple series of C_(m)C_(n) ring molecules,with parallel chains of m and n alkyl units(where m,n=6,8 or 10),by measuring their electrical conductance and Seebeck coefficients.Counterintuitively,the conductance of the symmetric C_(n)C_(n) rings is lower than that of the corresponding single chains(C_(n)),which is in contrast to the conductance superposition law in multi-channeled systems.Combined theoretical calculations reveal that the gauche conformation in a shorter chain fixed by another chain leads to the decreased conductance in alkyl rings,which originates from the phase-coherent tunneling and DQI in σ-conjugated systems.Our finding suggests that through appropriate conformation locking by cyclization,the covalent alkane system can exhibit DQI,which offers strategies for future designs of molecular electronic devices and materials.