Bandgap measurement of high refractive index materials by off-axis EELS
Journal article, Peer reviewed
Accepted version
Permanent lenke
http://hdl.handle.net/11250/2463211Utgivelsesdato
2017Metadata
Vis full innførselSamlinger
- Institutt for fysikk [2708]
- Publikasjoner fra CRIStin - NTNU [38672]
Sammendrag
In the present work Cs aberration corrected and monochromated scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) has been used to explore experimental set-ups that allow bandgaps of high refractive index materials to be determined. Semi-convergence and –collection angles in the µrad range were combined with off-axis or dark field EELS to avoid relativistic losses and guided light modes in the low loss range to contribute to the acquired EEL spectra. Off-axis EELS further supressed the zero loss peak and the tail of the zero loss peak. The bandgap of several GaAs-based materials were successfully determined by simple regression analyses of the background subtracted EEL spectra. The presented set-up does not require that the acceleration voltage is set to below the Čerenkov limit and can be applied over the entire acceleration voltage range of modern TEMs and for a wide range of specimen thicknesses.