Formation of orthorhombic (Zr,Ta)O2 in thin Zr-Ta-O films

The formation of orthorhombic (Zr,Ta)O-2 was found in annealed thin Zr-Ta-O films with various tantalum concentrations deposited by co-sputtering a ZrO2 target and a mixed ZrO2/Ta2O5 target. In the as-deposited state, all films were amorphous. After annealing, tetragonal (Zr,Ta) O-2 for [Ta]/([Ta] + [Zr]) <= 0.19 and orthorhombic (Zr, Ta) O-2 for [Ta]/([Ta] + [Zr]) > 0.19 were formed. Thin films with excess of tantalum ([Ta]/([Ta] + [Zr]) >= 0.5) decomposed into two orthorhombic phases upon crystallization: (Zr,Ta)O-2 and tantalum-rich (Ta,Zr)(2)O-5. The Rietveld analysis of X-ray diffraction patterns revealed that the crystal structure of (Zr,Ta)O-2 can be described with the non-centrosymmetric space group Pbc2(1). The broad range of tantalum concentrations, in which orthorhombic (Zr,Ta)O-2 is formed as a single crystalline phase, is promising for the use of this compound in ferroelectric field effect transistors. Published by AIP Publishing.