Controlling localized surface plasmon resonances in GeTe nanoparticles using an amorphous-to-crystalline phase transition.

Infrared absorption measurements of amorphous and crystalline nanoparticles of GeTe reveal a localized surface plasmon resonance (LSPR) mode in the crystalline phase that is absent in the amorphous phase. The LSPR mode emerges upon crystallization of amorphous nanoparticles. The contrasting plasmonic properties are elucidated with scanning tunneling spectroscopy measurements indicating a Burstein-Moss shift of the band gap in the crystalline phase and a finite density of electronic states throughout the band gap in the amorphous phase that limits the effective free carrier density.