Time- and temperature-resolved in situ investigation of the metal-induced crystallization of amorphous carbon thin films

The graphitization of amorphous carbon in thin film stacks with Ni was investigated in situ as a function of the initial stacking order, temperature and time by Rutherford backscattering spectrometry and Raman spectroscopy. Four different bilayer and triple layer stacks were exposed to heating ramps up to 700 °C. The graphitization occurred simultaneously with a layer exchange (LE) and was completed during the applied heating ramp. The temperature-resolved measurements allowed the determination of the onset temperatures and transition rates for the respective stacking order. Finally, the activation energies for the graphitization of the amorphous carbon were estimated for both LE directions. In combination with thermodynamic calculations,
this in situ study allowed to identify metal-induced crystallization with LE via wetting and diffusion along grain boundaries as mechanism responsible for the graphitization of amorphous carbon thin films in contact with Ni, instead of bulk dissolution/precipitation. The proposed model can potentially be used to estimate the catalytic transformation of group 14 elements in contact with transition metals.