  We experimentally demonstrate that the interaction between plasma and
nanometer-sized semiconductor quantum dots (QDs) is directly connected to a
change in their photoluminescence (PL) spectrum. This is done by taking
in-situ, high resolution, and temporally-resolved spectra of the light emitted
by laser-excited QDs on an electrically floating sample exposed to a low
pressure argon plasma. Our results show a fast redshift of the PL emission peak
indicating the quantum-confined Stark effect due to direct plasma-charging of
these nanostructures and the substrate surface, while other plasma-induced
(thermal and ion) effects on longer time scales could clearly be distinguished
from these charging effects. The presented results and method open up novel
pathways to direct visualization and understanding of fundamental
plasma-particle interactions on nanometer length scales.
