Conventional silicon-based devices are approaching the scaling limits toward super miniaturization, where the quantum size effect naturally emerges with increasing importance. Exploring the quantum size effect may provide additional functionality and alternative architectures for information processing and computation. Scanning tunneling microscopy/spectroscopy is an ideal tool to explore such an opportunity as it can construct the devices in an atom-by-atom fashion and investigate their morphologies and properties down to the atomic level. Utilizing nanocorrals as examples, the quantum size effect is demonstrated to possess the great capability in guiding the adatom diffusion and the self-assembly, controlling the statistical fluctuation, tuning the Kondo temperature, etc. Besides these fundamentals, it also shows strong potential in logic operations as the basic logic gates are constructed.
We present an unexpectedly strong influence of the proximity effect between the bulk Ru(0001) superconductor and atomically thin layers of Co on the crystal structure of the latter. The Co monolayer grows in two different modifications, such as hcp stacking and a reconstructed ε-like phase. While hcp islands show a weak proximity effect on Co and a little suppression of superconductivity in the substrate next to it, the more complex ε-like stacking becomes almost fully superconducting. We explain the weak proximity effect between Ru and hcp Co and the rather abrupt jump of the superconducting order parameter by a low transparency of the interface. In contrast, the strong proximity effect without a jump of the order parameter in the ε-like phase indicates a highly transparent interface. This work highlights that the proximity effect between a superconductor and a normal metal strongly depends on the crystal structure of the interface, which allows to engineer the proximity effect in hybrid structures.
Low dimensional nanostructures have attracted attention due to their rich physical properties and potential applications. The essential factor for their functionality is their electronic properties, which can be modified by quantum confinement. Here the electronic states of Gd atom trapped in open Fe corrals on Ag(111) were studied via scanning tunneling spectroscopy. A single spectroscopic peak above the Fermi level is observed after Gd adatoms are trapped inside Fe corrals, while two peaks appear in empty corrals. The single peak position is close to the higher energy peak of the empty corrals. These findings, attributed to quantum confinement of the corrals and Gd structures trapped inside, are supported by tight-binding calculations. This demonstrates and provides insights into atom trapping in open corrals of various diameters, giving an alternative approach to modify the properties of nano-objects.
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