Raman and electron field emission studies of the order–disorder transition in Ar ion implanted graphite

Abstract

Raman spectroscopy is used here to study the order–disorder transition in argon (Ar) ion implanted graphite where the sp2 hybridization is retained with presence of defect sites as electron field emitter. Oscillator strengths of the first-order and second-order Raman scattering are used to characterize the phase transition from graphite to amorphous carbon. Graphite transforms into amorphous carbon above a threshold fluence of Ar ions. Analysis of Gibb’s free energy can permit a rough identification of the threshold fluence for the formation of amorphous carbon. Raman spectra also reveal similar threshold fluence when transformation from graphite to amorphous carbon takes place. Raman spectroscopy can be efficiently used to calculate excess free energy which can lead to instability of graphite. Modifications of the surface of graphite are also investigated here by electron emission studies. Ar ions modify the electron emission properties of the ion irradiated graphite. The enhanced electron emission has been observed due to introduction of the ion irradiation induced defect sites in amorphous carbon.