We demonstrate large rectification ratios (> 100) in single-moleculejunctions based on a metal-oxide cluster (polyoxometalate), using a scanningtunneling microscope (STM) both at ambient conditions and at low temperature.These rectification ratios are the largest ever observed in a single-moleculejunction, and in addition these junctions sustain current densities larger than10^5 A/cm^2. By following the variation of the I-V characteristics withtip-molecule separation we demonstrate unambiguously that rectification is dueto asymmetric coupling to the electrodes of a molecule with an asymmetric levelstructure. This mechanism can be implemented in other type of molecularjunctions using both organic and inorganic molecules and provides a simplestrategy for the rational design of molecular diodes.
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机译：我们使用扫描隧道显微镜（STM）在环境条件和低温下都证明了基于金属氧化物簇（多金属氧酸盐）的单分子结中的大整流比（> 100），这是有史以来最大的整流比。单分子结，此外，这些结的电流密度大于10 ^ 5 A / cm ^ 2。通过遵循随着尖端分子分离的I-V特性的变化，我们明确地证明了整流是由于与具有不对称能级结构的分子的电极的不对称偶联而引起的。该机制可以在使用有机和无机分子的其他类型的分子结中实现，并为分子二极管的合理设计提供了简单的策略。
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