Photoemission properties of LaB6 thin films for the use in PIDs

For the improvement of a commercially available photo ionization detector (PID) with respect to its gas selectivity and sensitivity, a thin emitter film (≈ 20nm) of lanthanum hexaboride (LaB₆) was integrated performing the gas detection by photo emitted electrons. To confirm the chosen emitter material´s suitability as a photocathode, analyses were performed by X-ray diffraction (XRD) and ultraviolet photoelectron spectroscopy (UPS). Hereby, thin LaB₆ films sputtered with higher argon flow rate and sputtering power produced a (100)-oriented film texture yielding work functions in the range of 3.42 to 4.05 eV, accordingly. Photoemission measurements were also realized, whereby quantum efficiency (QE) of thin LaB₆ films is still too low compared to laser driven photocathodes when excited by 4.5 eV photons.