Interfacial reactions between thin rare-earth-metal oxide films and Si substrates

Rare-earth-metal oxide films (Ln(2)O(3); Ln=Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, and Yb) between 20 and 30 nm thick were grown on Si substrates by using a pyrolysis method. We found that a silicate (LnSiO) layer and a s ilicon oxide layer were formed at the interface between oxides and substrat e after postannealing. The infrared absorption of the Si-O-Ln bonds increas ed as the postannealing temperature rose. The Si-O-Ln bond formation strong ly depended on the ion radii of the rare-earth elements. We conclude that a n interfacial silicate layer can easily be formed by a reaction with Si ato ms diffusing from the substrate for oxides with larger ion radii. This is b ecause such oxides may have a larger space between atoms. The quantity of S i-O-Si bonds also increased after postannealing. The increase in the Si-O-S i bonds for Ln(2)O(3) was independent of the elements, and almost the same as the increases for Ta2O5 and ZrO2. (C) 2001 American Institute of Physics .