Effect of CaRuO3 interlayer on the dielectric properties of Ba(Zr,Ti)O3 thin films prepared by pulsed laser deposition

Abstract

Ba͑Zr 0.2 Ti 0.8 ͒O 3 ͑BZT͒ thin films on Pt͑111͒ / Ti/ SiO 2 /Si͑100͒ substrates without and with CaRuO 3 ͑CRO͒ buffer layer were fabricated at 650°C in situ by pulsed laser deposition. The BZT thin films showed a dense morphology, many clusters are found on the surface images of BZT/Pt films, which are composed by nanosized grains of 25-35 nm; the average grain size of BZT/CRO films is about 80 nm, which lager than that of BZT/Pt thin film. The dielectric constants and dissipation factors of BZT/Pt and BZT/CRO thin films were 392 and 0.019 and 479 and 0.021 at 1 MHz, respectively. The dielectric constant of BZT/Pt and BZT/CRO thin films changes significantly with applied dc bias field and has high tunabilities and figures of merit of ϳ70% and 37 and 75% and 36, respectively, under an applied field of 400 kV/ cm. The possible microstructural background responsible for the high dielectric constant and tunability was discussed. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2360177͔ Barium strontium titanate ͑Ba, Sr͒TiO 3 ͑BST͒ thin films have currently become very attractive for applications in decoupling capacitors, storage capacitors, dynamic randomaccess memory, and tunable microwave devices. 1,2 The large electric field-depended dielectric constant can be used for devices such as tunable oscillators, filters, and phase shifters. In such devices, it is desirable to have a high dielectric tunability in a certain electric field range and low dielectric loss. Ba͑Zr y Ti 1−y ͒O 3 ͑BZT͒ is a possible choice as an alternative to BST in the fabrication of ceramic capacitors 3,4 because Zr 4+ is chemically more stable than Ti 4+ . The ferroelectric phase transition at the Curie temperature ͑T C ͒ in BZT bulk ceramics is known to change significantly with Zr content. BZT ceramics exhibit a diffuse phase transition and have high tunability in compositions with y ജ 0.20. [3][4][5][6] The fabrication of BZT thin films by rf-magnetron sputtering, 7 sol-gel method, 8 and pulsed laser disposition ͑PLD͒, 9 and their dielectric properties have been reported recently. Many efforts have been made to improve the dielectric properties of the BST thin film capacitors, including using conductive oxide electrodes such as ͑Ba, Sr͒RuO 3 , 10 ͑La 0.7 Sr 0.3 ͒MnO 3 , 11 LaNiO 3 , 12 and yttrium barrium copper oxide ͑YBCO͒. 13 The effects of CaRuO 3 buffer layer on the dielectric properties and tunability of BZT films have not yet been reported. In this work, Ba͑Zr 0.2 Ti 0.8 ͒O 3 thin films growth on Pt/ Ti/ SiO 2 / Si substrate without and with CaRuO 3 buffer layer were prepared by pulsed laser disposition. The orientation characteristics of grains, dielectric properties, tunability, and figure of merit of the columnar-grained Ba͑Zr 0.2 Ti 0.8 ͒O 3 thin films on Pt/ Ti/ SiO 2 / Si substrate without and with CaRuO 3 buffer layer are also reported.CaRuO 3 ͑CRO͒ bottom electrode layer was grown on Pt/ Ti/ SiO 2 / Si substrates at 750°C by rf-magnetron sputtering and using a CRO target. Ba͑Zr 0.2 Ti 0.8 ͒O 3 ͑BZT͒ thin films were gr...

Effects of buffer layers on the orientation and dielectric properties of Ba(Zr0.20Ti0.80)O3 thin films prepared by sol–gel method

“…It has been proposed that the reduction in e r in ferroelectric thin films can be explained by the existence of an interfacial 'dead layer' at one or both metal electrodes with poor dielectric properties [2]. Use of the conductive oxide electrodes, such as (La, Ca) MnO 3 , CaRuO 3 and LNO, can decrease the thickness of the dead layer and enhance the dielectric constant [5,19,20]. A series of values of 100, 150 and 250 at 1 MHz have been reported for BZT ( 20 80 ) films on Pt-coated Si substrates with various deposition temperatures prepared by RF magnetron sputtering [21].…”

Electrical and piezoelectric properties of BiFeO3 thin films grown on SrxCa1−xRuO3-buffered SrTiO3 substrates

“…1, [12][13][14]16,17 The lattice constants of pseudo-cubic SCRO are 3.92 Å , 3.89 Å , 3.87 Å , and 3.84 Å , for x ¼ 1, 0.67, 0.33, and 0, respectively (as shown below). The lattice constant of bulk BFO is 3.96 Å , which is clearly larger than that of SCRO.…”

Microstructure and Electrical Conductivity of CaRuO<SUB>3</SUB> Thin Films Prepared by Laser Ablation

“…2,3) Since CRO and SRO have a slightly distorted GdFeO 3 -type orthorhombic structure (Pnma), they can be considered as having a pseudocubic perovskite structure. SRO thin film has been widely studied as an electrode for typically ferroelectric perovskite oxide because of its good lattice matching; however, the magnetic phase transition of SRO (T C ¼ 160 K) restricts its application to magnetic devices operating at low temperatures.…”