Microstructure and dielectric properties of (Ba,Sr)TiO 3 thin film produced by the polymeric precursor method
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E.B. Araujo Department of Physics, Federal University of Sa˜o Carlos-UFSCar, 13560-905 Sa˜o Carlos, SP, Brazil
E.R. Leite Department of Chemistry, Federal University of Sa˜o Carlos-UFSCar, 13560-905 Sa˜o Carlos, SP, Brazil
J.A. Eiras Department of Physics, Federal University of Sa˜o Carlos-UFSCar, 13560-905 Sa˜o Carlos, SP, Brazil
E. Longo Department of Chemistry, Federal University of Sa˜o Carlos-UFSCar, 13560-905 Sa˜o Carlos, SP, Brazil
J.A. Varela Institute of Chemistry, Paulista State University, 14801-970 Araraquara, SP, Brazil
M.A. Pereira-da-Silva Sa˜o Carlos Institute of Physics, Sa˜o Paulo State University, 13560-970 Sa˜o Carlos, SP, Brazil (Received 19 July 1999; accepted 7 February 2000)
BaxSr1−xTiO3 (x ⳱ 0.6) (BST) thin films were successfully prepared on a Pt(111)/TiO2/SiO2/Si(100) substrate by spin coating, using the polymeric precursor method. BST films with a perovskite single phase were obtained after heat treatment at 700 °C. The multilayer BST thin films had a granular structure with a grain size of approximately 60 nm. A 480-nm-thick film was obtained by carrying out five cycles of the spin-coating/heating process. Scanning electron microscopy and atomic force microscopy analyses showed that the thin films had a smooth, dense, crack-free surface with low surface roughness (3.6 nm). At room temperature and at a frequency of 100 kHz, the dielectric constant and the dissipation factor were, respectively, 748 and 0.042. The high dielectric constant value was due to the high microstructural quality and chemical homogeneity of the thin films obtained by the polymeric precursor method. I. INTRODUCTION
Many perovskite thin films have been extensively investigated due to their interesting dielectric properties.1–5 Perovskite compounds such as PLT,6 PZT,7 BaTiO3,8 SrTiO3,9 and (Sr,Ba)TiO3 (BST)10–12 have been studied for the dielectrics of dynamic random-access memory (DRAM) capacitors. It has been reported that nonswitching cubic paraelectric materials (nonferroelectric) should offer significant advantages over their spontaneously polar (ferroelectric) counterparts for unipolar nonswitching devices, that is, capacitive charging and discharging operations. Among these paraelectric materials, PLT, SrTiO3, and BST have been intensively investigated owing to their high relative dielectric constant coupled with good thermal stability. Currently, BST is regarded as the most promising material for high-density DRAM applications.13,14 1176
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J. Mater. Res., Vol. 15, No. 5, May 2000 Downloaded: 15 Mar 2015
Several deposition methods for BST films have been investigated, including radio frequency (rf)-sputtering,15 laser-ablation,16 activated reactive evaporation,17 ionbeam sputtering,18 metalorganic chemical vapor deposition (MOCVD), 19 sol-gel, 20,21 and metalorganic decomposition (MOD)22 techniques. Horikawa et al.23 prepared BST thin films by a rf-sputtering method with a dielectric constant ranging from 190 to 700 at room temperature. Sigov and Vorotilov24 reported a dielec
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