Sample carrier

For trace analyses of granular residues, a carrier is required that serves as sample support and as a totally reflecting mirror. They should be highly reflective and optically flat.

The roughness should be less than 5 nm within an area of 1 mm², corresponding to about one hundredth of the mean wavelength of the visible light.

The waviness should less than 0.001° within an area of about 1 cm², corresponding to a radius of curvature of about 600 m.

Furthermore, carriers should be free of impurities so that no blank values appear for the elements of interest. The carrier material itself must not produce fluorescence peaks in the spectral region to be considered. In addition the carriers have to be chemically inert in relation to strong acids and organic solvents. The carrier should be easy to clean and preferable inexpensive.

Several materials have been used, being fused quartz the most commonly used. The list of other possible materials includes Plexiglas (polymethyl methacrylate), Glassy carbon, boron nitride and synthetic Sapphire, as well as single element materials like Si and Ge.