Correlating The Structural, Chemical, And Optical Properties At Nanometer Resolution

Valence electron spectroscopic imaging (VESI) techniques, taking advantages of the energy-losses suffered by inelastic scattering of the fast electrons in the transmission electron microscope, offer an inherently high spatial resolution to characterize the electronic structure of materials close to the Fermi level. Here we demonstrate that the combination of an electron monochromator and a highly dispersive imaging energy filter, which has become available only recently, allows reliable measurements of local bandgaps on the nanometer scale. In addition, the correlations of structural, chemical, and optical properties can be revealed via VESI using monochromated electrons with a high spatial resolution.