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Glow Discharges

Glow Discharges

Introduction

This Glow Discharge Laboratory of optical emission spectroscopy is part of The Spectroscopy Net, a free and open resource originally designed by Dr Richard Payling of Surface Analytical, for Spectroscopists everywhere and everyone interested in Spectroscopy and its application. This is a non-commercial website, based on private initiative to promote knowledge about Glow Discharges as an analytical tool.


Glow Discharge Spectroscopy (GDS) provides rapid, direct bulk analysis and depth profiling analysis of solids: metals, powders, polymers, glasses and ceramics. Glow Discharge Optical Emission Spectrometry (GD-OES) employs a glow discharge source and one or more optical spectrometers.

The principle of operation is fairly easy to understand. In a glow discharge, cathodic sputtering is used to remove material layer by layer from the sample surface. The atoms, removed from the sample surface, migrate into the plasma where they are excited through collisions with electrons or metastable carrier gas atoms. The characteristic spectrum emitted by this excited atoms is measured by the spectrometer.

Find out more about spectroscopy on our web pages.

A Glow Discharge Optical Emission Spectrometer (GD-OES) comprises a glow discharge source and one or more optical spectrometers. A schematic layout is given in the image abouve. The spectrometer displayed here uses a concalve grating in the Rowland circle or Paschen-Runge configuration and photomultiplier tubes for the light detection.

The use of solid state detetectors, CCD's and photo diode array's have become a common alternative for PM tubes. These detectors allow the acquisition of the entire spectrum, or at least a large portion of it, but are usually slower then PM tubes and therefore not suitable for very short acquisition times used in thin film analysis.

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