Synthesis of LaB6 micro/nano structures using picosecond (Nd:YAG) laser and its field emission investigations

Micro/nano structures have been obtained by laser surface treatment on sintered LaB₆ pellets employing a picosecond pulsed Nd:YAG laser at a pressure of ∼1×10⁻³ mbar. The X-ray diffraction pattern of the laser treated pellet shows a set of well defined diffraction peaks, indexed to the cubic phase of LaB₆ only. The scanning electron microscope studies reveal formation of micro and nano structures upon laser treatment and the resultant surface morphology is found to be strongly influenced by the laser fluence. Field electron emission studies made on the LaB₆ pellet, treated with optimized laser fluence, have been performed in a planar diode configuration under ultra high vacuum conditions. The threshold field required to draw an emission current density of ∼10 μA/cm² has been found to be ∼2.3 V/μm and a current density of ∼530 μA/cm² has been drawn at an applied field of 5.2 V/μm. The Fowler-Nordheim plot is found to be linear in accordance with the quantum mechanical tunneling phenomenon, confirming the metallic nature of the emitter. The emission current at the pre-set value ∼10 μA shows very good stability over a period of more than 3 hours. The present results emphasize the effectiveness of a picosecond laser treatment towards fabrication of a nano metric LaB₆ emitter for high current density applications.