X-ray near total external fluorescence method: Experiment and analysis

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Abstract
The synchrotron x-ray near total external fluorescence technique is used to measure the concentration profiles of elements near a sample surface along its surface normal. This novel nondestructive technique is capable of providing information about the concentration profiles on a length scale of tens to hundreds of angstroms from the sample surface. It does not require vacuum and can be applied at ambient pressures. Concentration profiles of virtually all the elements in the periodic table can be investigated using this technique. The lower limit of detection is approximately equivalent to (1)/(10) of a monolayer coverage. The technique is particularly useful in applications where the fluorescence signal originating from a thin surface layer can be normalized against that originating from the same element in the bulk of the sample. The experimental procedure and the data analysis are demonstrated using experimental results of metal-ion segregation from a liquid solution to a liquid/air interface.