Eutectic and amorphous phase formation at Au/Cr/Si thin film interface by nanoindentation and annealing

Nanoindentation tests are performed on as-deposited Au/Cr/Si thin films to depths of 300 nm and 1000 nm, respectively. The indentations in as-deposited and annealed specimens are examined using transmission electron microscopy (TEM). The unloading curve of the specimen indented to 300 nm has a smooth profile, while that of the specimen indented to 1000 nm has a pop-out feature at a critical load of 100 mN. The hardness and Young's modulus of the Au/Cr/Si thin films are determined to be 1.7 GPa and 88 GPa, respectively. A strong correlation is found between the indentation depth, the annealing temperature and the microstructural changes induced in the thin films. A chain-like island structure is observed in the as-deposited specimen indented to 1000 nm and a pile-up of the thin-film material is observed around the indentation site. However, no microstructural change is evident in the as-deposited specimen indented to 300 nm. The greater deformation associated with an indentation depth of 1000 nm followed by annealing at 523 K or 623 K results in the formation of amorphous phase within the indentation zone. At the highest annealing temperature of 723 K, a mixed microstructure comprising amorphous and rod-like eutectic phase is observed.