On the optical measurement of microparticle charge using quantum dots

TL;DR

This paper explores a novel optical method using quantum dots to measure microparticle charge in plasma environments by detecting Stark shifts in photoluminescence spectra, proposing a new charge microsensor design.

Contribution

It introduces a quantum dot-based optical approach for microparticle charge measurement, combining theoretical calculations and experimental insights.

Findings

Measurable Stark shifts are achievable with surface diffusion of surplus electrons.

Quantum dots can serve as sensitive probes for local electric fields in plasma.

A potential design for a quantum-dot-based charge microsensor is proposed.

Abstract

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.