  We investigated the possibility of using a layer of quantum dots (QDs)
deposited on the microparticle surface for the measurement of the charge the
microparticle acquires when immersed into a plasma. To that end, we performed
the calculations of the Stark shift of the photoluminescence spectrum of QDs
caused by the fluctuating local electric field. In our calculations, we assumed
the plasma-delivered surplus electrons to be distributed on the surface of a
microparticle. According to our calculations, the Stark shift will acquire
measurable values when the lifetime of the quasi-stationary configuration of
the surplus electrons will be determined by their diffusion along the surface.
Experiments with flat QD-covered floating plasma-facing surfaces suggest that
measurable Stark shift of the photoluminescence spectrum can be achieved. Based
on our model, modern microscopic plasma-surface interaction theories and
analysis of the experiments, we suggest the possible design of the charge
microsensor, which will allow to measure the charge accumulated on its surface
by means of visible-light optics.
