Influence of electron-beam parameters on the radiation-induced formation of graphitic onions

It is shown that to form spherical graphitic onions by intense electron bombardment of graphitized carbon inside the electron microscope, irradiation must be performed at energies above the threshold of elastic atomic displacement, and at beam current densities higher than about 150 A cm(-2). Under these strong non-equilibrium conditions, it is possible to obtain the dynamic stability of the spherical shells, which appear fundamentally unstable in absence of irradiation.