Crystallization of ternary amorphous Ni-Y-Al films observed by scanning tunneling microscopy

Ternary thin Ni90-xYxAl10 films have been prepared by using cocondensation method under ultrahigh vacuum condition. Films with a wide concentration ra nge between Ni80Y10Al10 and Ni20Y70Al10 were found to be amorphous. With an addition of 10 at.% Al the thermal stability of binary amorphous NiY has b een enhanced. This is caused by a more closely packed structure and the bon dings between Al and Ni, Y may also play an important role. The surface inv estigation by scanning tunneling microscopy suggests that the atom redistri bution and the crystallization have been limited in the clusters with a siz e of about 10.5 nm. The nanosized amorphous clusters of Ni80Y10Al10 film ha ve changed to nanosized crystalline with the same size of about 12.3 nm whe n crystallization occurred.