Vertically aligned cerium hexaboride nanorods with enhanced field emission properties

Cerium hexaboride is a well-known material for the filaments of electron microscopes due to its field emission properties (high brightness electron source) and its long service life. The synthesis of cerium hexaboride (and most other borides) normally requires very high temperatures (1500 °C–1700 °C) and high pressures. Thus, the low temperature synthesis of cerium hexaboride at ambient pressure is a challenge. The present study highlights the synthesis of vertically aligned cerium hexaboride nanorods which offer better field emission properties with the highest field enhancement factor reported so far. The optimization of the process for obtaining vertically aligned cerium hexaboride nanorods involves three different stages. First, the low temperature synthesis of polycrystalline cerium hexaboride; second, the fabrication of cerium hexaboride films having vertically oriented nanorods (by spin coating and slow evaporation) and third, the enhancement of the field emission properties. The synthesis of cerium hexaboride nanorods has been carried out by a low temperature borothermal reduction process using a cerium precursor (synthesized via a reverse micellar route and a hydrothermal route) and boron as the starting materials. The borothermal reduction of the cerium precursors has been carried out at low temperature (∼1300 °C) and ambient pressure in an inert atmosphere. The field emission studies of the vertically aligned nanorods of diameter 30 nm and 200 nm show a field enhancement factor of 3863 and 3658, respectively, which is nearly seven-fold higher than the maximum field enhancement factor known so far