Crystallization of Ternary Amorphous Ni-Y-AI Films Observed by Scanning Tunneling Microscopy

Ternary thin Ni_90-xY_xAl₁₀ films have been prepared by using cocondensation method under ultrahigh vacuum condition. Films with a wide concentration range between Ni₈₀Y₁₀Al₁₀ and Ni₂₀Y₇₀AI₁₀ were found to be amorphous. With an addition of 10at.% AI the thermal stability of binary amorphous NiY has been enhanced. This is caused by a more closely packed structure and the bondings between AI and Ni, Y may also play an important role. The surface investigation by scanning tunneling microscopy suggests that the atom redistribution and the crystallization have been limited in the clusters with a size of about 10.5nm. The nanosized amorphous clusters of Ni₈₀Y₁₀Al₁₀ film have changed to nanosized crystalline with the same size of about 12.3nm when crystallization occurred.