A total of 3000 Angstrom Tb followed by 200 Angstrom Si (to reduce oxidation of Tb during annealing) was deposited onto SiO2. The samples were annealed at 500 degrees C from 7 to 97 min in HV. Rutherford backscattering (RBS) studies were performed on the annealed Tb on SiO2 samples. A real-time RES technique was also used to study the effect of annealing. The sample was quickly heated to 320 degrees C and, thereafter, ramped at 1 degrees C/min up to 600 degrees C. A similar experiment was repeated with Dy but without a capping Si layer. The real-time RES technique for SiO2/Dy was done by heating the sample quickly to 520 degrees C and keeping it constant at this temperature. The SiO2/Tb sample was transformed to SiO2(substrate)/silicide/oxide (the reaction of the cap layer ignored) after 7 min at 500 degrees C. After prolonged annealing at high temperatures, both the SiO2/Tb and SiO2/Dy samples were transformed to SiO2 (substrate)/metal oxide/metal silicide (with oxygen)/metal oxide.