Fig. 9: Gold in silicon allows recrystallisation at reduced temperatures.
From: Semiconductor core fibres: materials science in a bottle

a Phase diagram for Au–Si, showing the reduction possible. b End point of a gold-removal sweep, where sudden power reduction allowed excess gold to crack the cladding, leaving visible eutectic structure in a thin layer and small metal droplets on the outside of the glass. Features: I: gold droplets, II: eutectic film inside glass crack, III: purified silicon and IV: untreated gold-silicon alloy. Scale bar 0.1 mm.