薄膜厚度对纯水基溶胶-凝胶法制备Hf0.5Zr0.5O2纳米薄膜相转变的影响

Nano-Hf0.5Zr0.5O2 thin films were prepared on Si substrates by sol-gel processes to reveal their surface, structural and chemical properties. The exotherm peak at 496 C related to crystallization was observed in the DSC data of the Hf0.5Zr0.5O2 precursor. AFM images revealed the film surfaces were smooth and flat, no pores and micro-cracks were discernable. By fitting the XRR curves, the film thickness, density and surface roughness data were obtained. The film thickness was proportional to the number of spin coating cycles, with a deposition rate of 16.6 nm per cycle. The density increased significantly from 5.4 to 8.0 g/cm3 after annealing at 700 C. The effect of thickness on the crystal structure of Hf0.5Zr0.5O2 films was examined. Addition of ZrO2 helped to partially stabilize the tetragonal structure of HfO2. While stabilization of the tetragonal phase in Hf0.5Zr0.5O2 films could be maintained only when the thickness was below 12.9 nm. A further increase in the thickness led to the films consisting of a mixture of tetragonal and monoclinic phases, which should be attributed to a reduction of the surface energy contribution.