After calibration, glow discharge optical emission spectoscopy can provide a quantitative depth profile (QDP) or compositional depth profile (CDP) of materials. A typical example, an eight years old computer hard disc is shown at the left. Both results are displayed with courtesy of Max Aeberhard, EMPA Thun, CH.
The upper graphic shows the outer layers of the computer hard disk: a carbon film, followed by Cobalt and Chromium layers. At a depth of 75 nm the Nickel-Phosphate layer starts.
The lower graphics shows the same analysis on the µ-meter scale. Here we can distinguish the 5µm thick NiP treatment on the aluminium-magnisium alloy.
The expampel demonstrates the ability of GDOES to analysis in a single run both nano-meter thin layers, µm thick layers and the bulk-material.
The field of application of glow discharge optical emssion spectrometry is fairly wide :
- Steel (low and high alloyed, leaded, re-sulphurised)
- Iron (as-cast, chilled-cast, grey, ductile)
- Aluminium (high Si, composites)
- Copper, Brass, Bronze (leaded),
- Low Melting Point Alloys, Solders (Sn, Pb)
- Powdered Metals
- Elements not in solid solution
- Galvanizing (EG, Hot Dip, Galvalume, Galvanneal, Galfan, Zinc Nickel)
- Clad (Aluminium)
- Oxide layers, corrosion studies
- Plating (Sn, Cr, Cd, Ni, Cu)
- Organic coatings
- Thermochemical treatments (Carburising, Nitriding, Carbonitriding)
- Electrochemical treatments
- Hard coatings made by PVD/CVD
It has been shown to be a successful analytical tool, whenever the elemental composition of the first few nanometers up to 100 µm of solid material must be investigated. Conductive material can be analysed using a direct current glow discharge, non-conducting materials require radio-frequency excitation of the plasma.
GD-OES has various acronyms: GD-AES, GDOS, SDL, GDA, GDS. The GD source (or GD lamp) used in most commercially available GDOES insturments are based on the original design of the Grimm source.
Topics of interest include: density, coating mass,Sputtering, Emission Yield, self-absorption, Calibration, spectral interferences, and RF (radio frequency) versus DC (direct current).