X-ray Fluorescence (XRF) analysis offers the simultaneous, multi-elemental characterization of a broad range of solid and liquid materials in a non-invasive manner. Its principle of operation relies on the property of each element in the periodic table to emit the so-called characteristic X-rays upon the ionization of its inner shell bound electrons. The elements characteristic X-rays exhibit unique energies, thus, using an appropriate energy dispersive spectrometer, the corresponding element can be firmly identified (qualitative analysis). The typical laboratory-based XRF instrumentation utilizes X-ray tubes to induce inner-shell ionization of the sample’s constituent elements, whereas silicon-based detectors provide energy dispersion and sufficient resolution to distinguish adjacent elements in the periodic table. In air environment, the XRF analysis usually detects elements with Z>13 with optimum analytical sensitivity for most of the transition metals in bulk sample or thin films (down to few μg/g or nm-scale thickness layers).

The efficient focus of exciting X-ray beams at the micrometre scale (20-100 μm) is usually achieved by means of specialized optical elements called polycapillary X-ray lenses. By varying (increasing) the lens focal distance, the beam spot size can be also tuned compromising the spatial resolution versus the speediness of the measurement, especially when relatively large areas (~cm²) are probed.

The generation of elemental maps is aided by scanning the spectrometer head in 2D directions across the examined material surface and it is further optimized using on-the fly measurement protocols and almost real-time acquisition systems.