Optimized Field Emission from Graphene Sheets with Rare Earth Oxides.

This paper demonstrates a simple method to improve the field emission of graphene sheets (GSs) by coating them with thin films of rare earth oxides. The rare earth oxide films are coated on GS using drop coating, without changing the surface morphology, resulting in a remarkable improvement in the field emission properties of GSs. The field emission property of GSs is tunable and can be optimized by applying various rare earth oxide films at the appropriate level. It is found that the turn-on field of GSs is reduced from 4.2 V/mm to 1.7 V/mm by Gd₂O₃ and to 2.2 V/mm by La₂O₃. The threshold field of GS is also reduced from 7.8 V/mm to 3.4 V/mm and 4.8 V/mm, respectively. Field emission results indicate that the improvement is due to the low work function surface and more effective emission sites generated around the GS surface after coating. The field emission test and the emission pattern suggest that the field emission performance of GS can be significantly enhanced through the application of La₂O₃ and Gd₂O₃ coating, as well as by optimizing the concentration of rare earth oxides in the coating. Hence, the rare earth-coated GS can serve as a potential field emitter. [ABSTRACT FROM AUTHOR]