Femtosecond laser induced formation of graphene nanostructures in water and their field emission properties

Abstract

Nanostructured surfaces that possess specific structures, such as flower-like patterns, can offer great opportunities for field emission and sensor applications. However, the current research methods for texturizing graphene require high costs and harsh processing conditions regarding temperature, pressure, and catalysts. Here, we present a novel method that is easy, fast, and low-cost to create graphene microflowers with special nanostructured edges. In our experiment, we irradiate 800 nm femtosecond laser onto graphite foil submerged in distilled water. High-density, periodic nanofingers remained on the top of the upright flower petal structures perpendicular to the laser polarization. Scanning electron microscopy (SEM) imaging showed that the nanofingers have a uniform width of approximately 50 nm. Raman spectroscopy corroborated that the nanostructured surface shows sharper graphene characteristic peaks than those of the unirradiated original graphite foil. Lorenz fitting curve analysis showed that the micro/nano-structured graphene has average five layers. Their field emission properties were measured in a 10−5 Pa vacuum chamber, and the current density reached 1 mA cm−2 under a 5.5 V μm−1 electric field without inducing any thermal damage.