Controllable Si oxidation mediated by annealing temperature and atmosphere

Abstract The morphology evolution by thermal annealing induced dewetting of gold (Au) thin films on silicon (Si) substrates with a native oxide layer and its dependences on annealing temperature and atmosphere are investigated. Both dewetting degree of thin film and Au/Si interdiffusion extent are enhanced with the annealing temperature. Au/Si interdiffusion can be observed beyond 800 °C and Au–Si droplets form in both argon and oxygen (Ar + O 2 ) and argon and hydrogen (Ar + H 2 ) environments. In Ar + O 2 case, the passive oxidation (Si + O 2 → SiO 2 ) of diffused Si happens and thick silicon oxide (SiO x ) covering layers are formed. A high temperature of 1050 °C can even activate the outward growth of free-standing SiO x nanowires from droplets. Similarly, annealing at 800 °C under Ar + H 2 situation also enables the slight Si passive oxidation, resulting in the formation of stripe-like SiO x areas. However, higher temperatures of 950–1050 °C in Ar + H 2 environment initiate both the SiO x decomposition and the Si active oxidation (2Si + O 2 → 2SiO (g) ), and the formation of solid SiO x is absent, leading to the only formation of isolated Au–Si droplets at elevated temperatures and droplets evolve to particles presenting two contrasts due to the Au/Si phase separation upon cooling.