Field emission studies of pulsed laser deposited films on W and Re

Lanthanum hexaboride films were grown on tungsten and rhenium tips and foils by pulsed laser deposition. The X-ray diffraction spectra of the PLD LaB 6 films on both the substrates show crystalline nature with average grain size ∼ 125 nm . The field emission studies of pointed and foil specimens were performed in conventional and planar diode configurations, respectively, under ultra-high vacuum condition. An estimated current density of ∼ 1.2 × 10 4 A / cm 2 was drawn at the electric field of 3 × 10 3 and 6 × 10 3 V / μ m from the LaB 6 coated tips of tungsten and rhenium, respectively. The Fowler–Nordheim plots were found to be linear showing metallic behavior of the emitters. The field enhancement factors were calculated from the slopes of the Fowler–Nordheim plots, indicating that the field emission is from LaB 6 nanoscale protrusions present on emitter surfaces. The emitters were operated for long time current stability (3 h) studies. The post-field emission surface morphology of the emitters showed no significant erosion of LaB 6 films during 3 h continuous operation. The observed behavior indicates that it is linked with the growth of LaB 6 films on W and Re. These results reveal that the LaB 6 films exhibit high resistance to ion bombardment and excellent structural stability and are more promising emitters for practical applications in field emission based devices.