Lower crystallization temperature of sol-gel PbTiO_3 on Ti/Pt-coated substrates

摘要

PbTiO_3 (PT) thin films have been deposited by sol-gel on Pt/Si, SiO_2/Si, Pt/Ti/SiO_2/Si, and Ti/Pt/Ti/SiO_2/Si and annealed for 45 min in the 400-670 deg. C range. Analysis by x-ray diffraction (XRD) and spectroscopic ellipsometry shows that the Ti overlayer promotes early crystallization in the tetragonal perovskite phase, reducing the presence of a second phase, tentatively identified as pyrochlore, starting by 450 deg. C. The refractive index and extinction coefficient (n, k) of the PT film increase rapidly with the sintering temperature in the range of 450-570 deg. C and saturate by 570 deg. C to values of n varying from 2.4 to 2.9, and k from 0.03 to 0.3, over the l.65-2.95 eV range. Most of the increase of n is related to thin film densification.