Manipulating the anisotropy and field emission of lanthanum hexaboride nanorods

Abstract

The present study describes the controlled synthesis of lanthanum hexaboride nanostructures with efficient field emission properties. The synthesis is mediated by a nanostructured lanthanum hydroxide precursor, which is controlled by varying the capping agent and pH using a hydrothermal route. The effect of charge on the capping agent (surfactant) strongly affects the shape and size of the precursor (neutral surfactants lead to the formation of nanorods while a cationic surfactant results in the formation of particles). This precursor mediated route leads to lanthanum hexaboride nanostructures at much lower temperatures (∼500 °C lower than the conventional solid state route) and allows for variation of morphology of nanostructured films. Vertically aligned nanorods (30 nm × 200–400 nm), nanoparticles (25 nm) and sub-micron particles (0.2–0.25 microns) could be precisely obtained. Field emission studies of these vertically aligned nanorods show a very high field enhancement factor (4191), which is required for an efficient field emitter.