Diagnostics of low and atmospheric pressure plasmas by means of mass spectrometry

TL;DR

This paper demonstrates the use of mass spectrometry as a sensitive and direct method to analyze reactive species in low and atmospheric pressure plasmas, providing absolute densities and insights into plasma chemistry.

Contribution

It introduces a calibrated mass spectrometry technique for measuring neutral and ion species in atmospheric pressure plasmas, including metastable states.

Findings

Mass spectrometry effectively measures plasma composition at the surface.

The technique provides absolute densities of reactive species.

It can detect internally excited metastable species.

Abstract

The knowledge of absolute fluxes of reactive species such as radicals or energetic ions to the surface is crucial for understanding the growth or etching of thin films. These species have due to their high reactivity very low densities and their detection is therefore a challenging task. Mass spectrometry is a very sensitive technique and it will be demonstrated that it is a good choice for the study of plasma chemistry. Mass spectrometry measures the plasma composition directly at the surface and is not limited by existence of accessible optical transitions. When properly designed and carefully calibrated mass spectrometry provides absolute densities of the measured species. It can even measure internally excited metastable species. Here, measurement of neutral species and positive ions generated in an atmospheric pressure plasmas jet operated with He, hexamethyldisiloxane and O2 will be presented.