High temperature focused ion beam response of graphite resulting in spontaneous nanosheet formation

Abstract

This work presents an experimental study of a novel combination of a focused ion beam (FIB) with a heating stage to produce real-time microstructural imaging at elevated substrate temperatures from FIB exposed highly ordered pyrolytic graphite (HOPG). The surface modifications achieved by different angles of ion beam incidence and various substrate temperatures were investigated in situ by field emission scanning electron microscopy and afterwards by atomic force microscopy. The authors studied the formation and self-organization of ripples, porous structures, and graphite nanosheets (GNS), which appear spontaneously during FIB irradiation of HOPG. Here the evolution of pseudoperiodical ripples from small amplitudes to nanospikes with increasing ion fluences and the transformation into disorganized porous structures at higher temperatures was observed and further investigated. Moreover, the authors were able to induce the spontaneous formation of sheet like carbon nanostructures at substrate temperatures above T = 500 °C by controlling the scan speed and the ion fluence. These high aspect ratio crystalline GNS, several micrometers high and thinner than 60 nm, can be formed at predefined sites on the HOPG surface.