Thickness dependence of the electrical and electromechanical properties of Pb(Zr,Ti)O3 thin films

The electrical and electromechanical properties of Pb(Zr,Ti)O-3 (PZT) thin films are extensively investigated. The PZT thin films were prepared on Pt/MgO substrates by chemical solution deposition. For thick film deposition, the solutions with a relatively high metal concentration of 15-25 wt% are used. Film thickness is controlled up to 2.0 mum by repeating the spin coating, and all the 0.4, 1.0 and 2.0-mum-thick films exhibited well-saturated polarization hysteresis loops, with their differences being trivial. With an increase of film thickness from 0.4 mum to 1.0 mum, electric-field-induced strain increased significantly. The reason for the electromechanical properties' dependence on film thickness is examined by means of phenomenological calculation and by analyzing the temperature dependence of dielectic and ferroelectric properties of the films down to 20 K. The temperature-dependent polarization hysteresis loops and DC bias-dielectric constant curves indicate that thinner films possess potentially higher Curie temperature. The temperature-dependent strain loops from PZT films were measured using scanning probe microscopy; their temperature dependence was relatively small in the temperature range from 120 K to 320 K.