Electrical and pyroelectric properties of in-plane polarized lead lanthanum titanate thin film

Abstract

Pb 0.9 La 0.1 Ti 0.975 O 3 ͑PLT10͒ thin films were deposited on SiO 2 /Si(100) substrates coated with a ZrO 2 buffer layer. Studies by x-ray diffraction and scanning electron microscopy reveal that the ZrO 2 film consists of both tetragonal and monoclinic phases, with the tetragonal phase being the dominant one. The PLT10 film has a perovskite structure and the grains in the film have a rather uniform size of about 50 nm. By using interdigital transducer ͑IDT͒ electrodes the in-plane electrical properties, hysteresis loop, and pyroelectric coefficient of the PLT10 film were measured. The dielectric constant and loss factor vary only slightly with frequency in the range 10 3 -10 6 Hz, with the loss factor being less than 0.01 over the entire range. The leakage current density is lower than 2ϫ10 Ϫ8 A/cm 2 at a bias field of 5 kV/cm. The remnant polarization and coercive field are 12.6 C/cm 2 and 9.93 kV/cm, respectively. The film exhibits a reasonably high pyroelectric coefficient (95 C/m 2 K) after it has been poled by applying 120 V ac at 0. [1][2][3][4] These films have potential applications in a variety of devices including nonvolatile memories, optical switches, and infrared detectors. 5,6 Lead zirconate titanate ͑PZT͒ films were successfully deposited on ZrO 2 -passivated silicon substrates and were poled parallel to the film surface to give in-plane polarization. 7 Micromachined ultrasound arrays based on inplane polarized PZT films showed a 30 dB improvement in sensitivity. 8 In this work, PLT10 thin films were deposited on silicon substrates coated with ZrO 2 buffer layers. We investigated the in-plane electrical and pyroelectric properties of the PLT10 thin films by using interdigital transducer ͑IDT͒ electrodes. The films were found to exhibit good dielectric, ferroelectric, and pyroelectric properties in this in-plane configuration.The ZrO 2 buffer layer and PLT10 thin film were prepared by the metal-organic decomposition ͑MOD͒ method. A precise control of the solution concentration was important to produce high-quality, smooth, and crack-free films. To prepare the ZrO 2 solution, zirconium n-propoxide was added to distilled 2-methoxyethanol; the mixture was stirred at 120°C for 1 hr until the associated water was removed. After cooling to room temperature, the solution was filtered and a suitable amount of 2-methoxyethanol was added so as to give a concentration of 0.3 M. The raw materials for preparing PLT10 thin films were lead acetate trihydrate, lanthanum nitrate, and titanium isopropoxide. 2-methoxyethanol was used as the solvent. The preparation procedure of the metalalkoxide precursor solution has been described in detail elsewhere. 9,10 The substrate was a ͑100͒-oriented n-type silicon wafer coated with a 5.46-m-thick SiO 2 layer. ZrO 2 layers were deposited on the substrate by spin coating at 2500 rpm for 25 s. Each layer was pyrolyzed in O 2 at 600°C for 10 min. After depositing 20 layers of ZrO 2 , the resulting film was annealed in O 2 at 600°C for 1 hr. Another 20 layers of PLT10 were t...

Converse mode piezoelectric coefficient for lead zirconate titanate thin film with interdigitated electrode

“…Equation (30), can be applied in Stoney's formula shown in equation (15) to get the in-plane stress developed: …”

BST and Other Ferroelectric Thin Films by CCVD and Their Properties and Applications

“…PZT and La doped PZT (Pb 1-x/100 La x/100 (Zr y/100 Ti z/100 )O 3 , PLZT x/y/z) have been extensively investigated for applications, such as DRAM H. H. Kim et al, 1998), FRAM (Ramash et al, 2001; W. S. Kim et al, 1999), sensors and actuators for microelectromechanical systems (MEMS)(B. M. Xu, 1999;Polla and Francis, 1998), infrared detectors (Song et al, 2001;Kobune et al, 2001), due to their excellent dielectric, ferroelectric, piezoelectric, and pyroelectric properties. PLZT is transparent in the visible and near infrared region of the electromagnetic waves and has excellent electro-optical properties.…”

Impact of in-plane anisotropic strains on the dielectric and pyroelectric properties of Ba0.7Sr0.3TiO3 thin films

“…One major advantage is that they can operate at room temperature, thereby eliminating the need for expensive cooling systems. [7][8][9][10] Moreover, the integration of hybrid arrays of ferroelectric thin films detectors with silicon readout integrated circuits can offer high-performance infrared imaging. BST thin films are also considered as the candidate materials for pyroelectric sensors because of their relatively large nonlinear pyroelectric response at room temperature, good reliability, good sensitivity, and low cost.…”