Aluminum Nanoparticles as Fiducials for Nanoscale Temperature Measurements
In plasmon energy expansion thermometry (PEET), electron energy-loss spectroscopy (EELS) is used to determine the plasmon energy in a suitable thermometric material [1]. Since the plasmon energy scales with the material’s density, temperature changes can be determined using knowledge of the material’s thermal expansion coefficient. Many in situ transmission electron microscopy experiments could benefit from having thermometric fiducials, i.e. localized thermometers within the field of view. Nanoparticles of aluminum, with their narrow bulk plasmon resonance and large thermal expansion coefficient [2, 3], are particularly well suited to act as such fiducial thermometers.
Über die Abhängigkeit der charakteristischen Energieverluste von Temperatur und Streuwinkel
ZusammenfassungEs werden Experimente beschrieben, in denen mit Hilfe der Gegenfeldmethode die Abhängigkeit des mittleren Energieverlustes von der Objekttemperatur an Al und Ge gemessen wurde. Die Ergebnisse stimmen mit der Aussage überein, die sich aus der Plasmatheorie bei Berücksichtigung der thermischen Ausdehnung des Kristalls ergibt. Weiterhin wurden Form, Lage und Intensität der Energieverteilung der unelastisch gestreuten Elektronen in Abhängigkeit vom Streuwinkel untersucht. Auch hier konnten an Al die Aussagen der Theorie hinsichtlich der Größe des Verlustes und des maximalen Streuwinkels bestätigt werden.
Melting and supercooling studies in submicron Al particles using valence electron energy-loss spectroscopy in a transmission electron microscope
The crystallization behavior of Al and its alloys has been extensively investigated due to the importance of these structural materials. In this study, valence electron energy-loss spectroscopy in a transmission electron microscope was used to study changes that occur in the volume plasmon energy, and hence, the valence electron density, during heating and cooling through the melting temperature in submicron Al particles. The results show that a phonon anharmonicity causes a nonlinear change in the volume plasmon energy that is not present in the liquid phase after melting. The plasmon energy/valence electron density during supercooling is not a direct extrapolation from the liquid state and tends to stabilize, possibly due to local ordering in the liquid. The study also shows that damping of the plasmon excitations in liquid Al is faster compared to solid Al due to electron-phonon interactions and/or Anderson localization of electrons.