Multilayer formation during annealing of thin Tb layers on SiO2 substrates

Abstract

A 2000 Å layer of Tb followed by a 200 Å layer of Si was deposited onto an SiO2 substrate. The samples were annealed from 480°C for 4 min to 800°C for 120 min in a high vacuum (p⩽2×10−7 Torr). It was inferred from Auger depth profiles and peak shapes that the reaction between Tb and SiO2 starts by the dissociation of SiO2 at the Tb/SiO2 interface. The released oxygen diffuses into the deposited Tb, forming a Tb–O solid solution. Terbium silicide initially forms at the Tb/SiO2 interface. After annealing for 25 min at 480°C, terbium oxide started to grow next to the SiO2 substrate. After annealing for 80 min at 480°C, the oxide/silicide (with oxygen)/oxide layers were well separated on the SiO2 substrate. Annealing at 600°C for 16 min and at 800°C for 120 min resulted in an additional layer that formed next to the SiO2, which consists of Tb, Si and oxygen. We assume that this layer is the beginning of the formation of another silicide layer with embedded oxygen in the layer. The sample eventually consists of SiO2(substrate)/silicide (with oxygen)/metal oxide/silicide (with oxygen)/metal oxide. The metal oxides contain an Si concentration of <4 at.%. The depth profile of the sample annealed at 800°C for 120 min does not differ significantly from the depth profile of the sample annealed at 600°C for 16 min, except that the profiles show that the silicide layer of the 800°C annealed sample is more oxidized. © 1998 John Wiley & Sons, Ltd.