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.