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INSPECTION
Surface analyses to improve
PV thin films
Photovoltaic manufacturing is looking at every aspect to improve efficiencies
and yield as the industry seeks its place in the energy markets. Air Liquide
Electronic’s solar business group, now known as Balazs discuss applications
and problem solving cases where Glow Discharge Optical Emission
Spectroscopy (GD-OES) and Laser Ablation Inductively Coupled Plasma Mass
Spectrometry (LA ICP-MS) provide solutions for current industry challenges.
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Characterization of photovoltaic thin films for depth per minute and optical emission signals that are
profiling, elemental composition and metallic recorded at millisecond speeds it is possible to
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contamination is a growing requirement to perform both surface and bulk analyses for all
.solar
understand film characteristics, improve product types of photovoltaic thin films and materials.
quality and ultimately enhance photovoltaic
-pv-management.com
conversion efficiency in thin film products. As the name would imply with LA ICP-MS; the
Analytical methods used historically in the source for material sampling is the laser. Shown in
semiconductor industry such as SIMS, ESCA and Figure 2, a front-end laser is used as a sampling
Auger have some application, but for many thin device to any surface material. Gas phase species
films and applications, (GD-OES) and (LA ICP-MS), are generated and then introduced into an ICP-MS
provide more utility in solving problems and for ultimate ionization, separation and detection.
providing answers to the engineer. Similar to GD-OES, elements are detected in a
Issue V 2009
near simultaneous fashion with GD-OES able to
Shown in Figure 1a) GD-OES utilizes a small detect H, N, O, and C while LA ICP-MS is suitable
plasma between an anode and sample material simply for metal and near-metal elements.
that acts as the cathode to generate a “glow,”
excited atoms, and subsequent element specific With each technique briefly described, choosing
emission. The dynamics of the glow discharge GD-OES or LA ICP-MS for a specific PV thin film
source allows numerous applications not available application depends generally upon the thickness
with traditional surface analysis techniques of the film, the elements of interest and the
including analysis of sample materials that can be sensitivity required. Both techniques can be used Table 1: Comparison of
either conductive or non-conductive as well as to analyze any type of solid material and have near GD-OES and LA ICP-
simultaneous elemental detection across the simultaneous elemental detection. Relative MS advantages for PV
periodic table. With a sputtering rate of 1 – 10 µm advantages for each technique are shown (Table 1.) Thin Film analysis
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