Nanoscale mapping of the electron density at Al grain boundaries and correlation with grain-boundary energy

Abstract

Grain-boundary (GB) structures and energies are often calculated and have revealed correlations between the GB energy and change in electron density at the GB. In this work, the plasmon peak in valence electron energy-loss spectroscopy (VEELS) was used to determine the variation in electron density across four well-characterized GBs in Al, spanning a range of known GB energies. The results show that the plasmon energy is lower at the GB than in the adjacent grains due to a decrease in electron density, and the GB energy increases proportional to the density decrease. The decrease in electron density also extends further into adjacent grains with increasing GB energy, extending beyond the geometric changes, or physical width, revealed by electron microscopy. Plasmon damping also increases with increasing GB energy, indicative of increasing disruption of the electron density with increasing GB energy. These results demonstrate that VEELS can be a valuable tool for detecting small electron density changes at GBs, and this change clearly influences, and is correlated to, the GB energy.