Orientation controlling of PZT thin films derived from sol-gel techniques

Abstract

The factors that influence the crystal orientation of lead zirconate titanate (PZT) thin films fabricated by using sol-gel techniques on (111) preferred oriented Pt/Ti/SiO2./Si(100) substrates were systematically investigated. The crystallization treatment of PZT thin films was done at 650 ◦C for 30 min by using rapid thermal annealing (RTA). X-ray diffraction (XRD) analysis was used to identify the orientation of PZT thin films. The morphology was examined by using scanning electron microscopy (SEM). The different ratio of zirconium to titanium, the lead contents in precursor solutions, the modification of the PZT precursor and the thickness of PZT thin films have obviously effects on the formation of (111) or (100) preferred-oriented and random-oriented PZT thin films. It is concluded that controlling the orientation of PZT thin films can be realized by using the sophisticated sol-gel processing and normal (111) Pt/Ti/SiO2./Si(100) substrates. Electrical properties of ferroelectric thin films are strongly dependent on their crystallographic orientation, which determines the magnitude of switchable polarization of a thin film. Among the applications for which highly oriented PZT thin films will be of interest are pyroelectric detectors, optical disk storage system, optical waveguide devices, and spatial light modulators. A further benefit of orientation may be enhancing process integration of ferroelectric thin film and semiconductor technologies. Many studies for the control of a preferred orientation in PZT films are usually based on the substrate used. Most of them use various single crystals as substrates to fabricate the crystal alignment of the PZT thin films. For example, PZT films with (100), (110), and (111) textures can be obtained by using single-crystal SrTiO3 or MgO wafers of the same orientation [1]. But single-crystal substrates have economical problem for applications of the ferroelectric thin films. It is necessary to develop a method for the control of the PZT orientation using relatively cheaper substrates. RF magnetron sputtering [2], metal organic chemical vapor deposition (MOCVD) [3], and pulsed laser deposition (PLD) [4] methods have been widely utilized to produce highly oriented or epitaxial ferroelectric thin films. Chemical process has the advantages of feasible