Morphology tuning and electron emission properties of a carbonaceous LaB6 system obtained using a thermal plasma route

Abstract

In the present study, we report the morphological tuning of carbonaceous nanocrystalline lanthanum hexaboride (LaB₆) using an arc plasma route. It was possible to obtain different morphologies, namely: pebbles, rods and sheets, on a nano-scale by means of plasma assisted vapour phase growth and by varying the plasma current. At elevated plasma currents, as a consequence of graphite electrodes being used in the arc geometry, the synthesized product was obtained in the form of carbonaceous LaB₆ having a high degree of crystallinity. Detailed morphological analysis using electron microscopy has revealed that nanorods and nanosheets of carbonaceous LaB₆ can be grown by elevating the plasma currents. The field emission (FE) current was found to be enhanced from 200 μA cm⁻² to 660 μA cm⁻² for the hierarchical structure of nanosheets as compared to that of nanopebbles at a much reduced turn-on potential. A stable FE current is an important feature exhibited by all these LaB₆ nanostructures.