“Explosive” crystallisation of amorphous germanium in Ge/Al layer systems; comparison with Si/Al layer systems

The crystallisation of amorphous germanium in contact with aluminium was studied in Ge/Al layer systems by employing in situ and ex situ X-ray diffraction methods. Comparing Ge/Al and Si/Al systems, totally different crystallisation behaviours were observed. Amorphous Ge in contact with Al shows an “explosive” crystallisation at temperatures as low as 150 °C, whereas amorphous Si exhibits a gradual crystallisation accompanied by a simultaneous layer exchange between Si and Al layers. The observations have been interpreted on a thermodynamic basis.