Thermally activated crystallization of Nb2O5 grown on Pt electrode

The influence of the local crystallographic orientation of the polycrystalline bottom platinum electrode on the crystallization of niobium pentoxide thin films during their rapid thermal annealing was investigated by X-ray diffraction, X-ray reflectivity and transmission electron microscopy. The Nb2O5 thin films under study were reactively sputtered in a mixed O2/Ar atmosphere and subsequently subjected to the annealing in argon atmosphere at temperatures ranging from 500 C to 700 C. The X-ray diffraction confirmed a transition from the amorphous niobium oxide to the crystalline orthorhombic Nb2O5 for temperatures between 500 C and 600 C. The X-ray reflectivity measurements showed that the crystallization process was accompanied by a continuous increase of the electron density in Nb2O5 and by a rapid increase of the surface roughness at 700 C. It was further observed by transmission electron microscopy that Nb2O5 crystallizes selectively and that the crystalline domains of Nb2O5 possess a strong orientation relationship to the platinum from the bottom electrode. The orientation relationship (anti 111)Pt parallel (anti 1 anti 60)Nb2O5 was identified as the most beneficial one for crystallization of Nb2O5. (orig.)