Using energy-filtered transmission electron microscopy we measured surface-plasmon resonances of gold nanoplatelets with different shapes and edge lengths at high spatial resolution. We find equidistant maxima of the energy-loss probability along the platelet edges. The plasmon dispersion of the different geometries is very similar, i.e., hardly dependent on specimen shape. The experimental results are verified by means of finite-difference time-domain calculations which reveal the presence of wedge-plasmon polaritons propagating along the platelet edges. At platelet corners, apart from radiative losses, wedge-plasmon polaritons are partially reflected or transmitted to neighboring edges. The interference of all these contributions leads to the observed plasmon resonance modes. This is an essential step towards a thorough understanding of plasmon eigenmodes in prismatic nanoplatelets.
Grain boundaries (GBs) in polycrystalline Cu(In,Ga)Se2 thin films exhibit only slightly enhanced recombination, as compared with the grain interiors, allowing for very high power‐conversion efficiencies of more than 20% in the corresponding solar‐cell devices. This work highlights the specific compositional and electrical properties of Cu(In,Ga)Se2 GBs by application of appropriate subnanometer characterisation techniques: inline electron holography, electron energy‐loss spectroscopy, and atom‐probe tomography. It is found that changes of composition at the GBs are confined to regions of only about 1 nm in width. Therefore, these compositional changes are not due to secondary phases but atomic or ionic redistribution within the atomic planes close to the GBs. For different GBs in the Cu(In,Ga)Se2 thin film investigated, different atomic or ionic redistributions are also found. This chemical flexibility makes polycrystalline Cu(In,Ga)Se2 thin films particularly suitable for photovoltaic applications.
We report on the development of the dark-field inline electron holography technique and its application to map strain in technologically relevant structures, using as an example the strain-engineered gate channel in a 45 nm metal-oxide semiconductor field-effect transistor structure. We show that this technique combines a large field of view of several micrometers with high precision ͑better than 0.01%͒, high spatial resolution ͑better than 1 nm͒, and very loose experimental requirements not possible with any other technique currently available.
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