Structural phase evolution of strontium-doped lead titanate thin films prepared by the soft chemical technique
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eal Laborato´rio Interdisciplinar de Eletroquı´mica e Ceraˆmica (LIEC), Centro Multidisciplinar Para Desenvolvimento de Materiais Ceraˆmicos (CMDMC), Departamento de Química, Universidade Federal de Sa˜o Carlos (UFSCar), Via Washington, Km 235, CP-676, CEP-13565-905, São Carlos, S. P., Brazil, and Centro de Cieˆncias da Natureza (CCN), Departamento de Química, Universidade Federal do Piauı´ (UFPI), Teresina, PI, Brazil
P.S. Pizani Departamento de Física, Universidade Federal de Sa˜o Carlos (UFSCar), Via Washington, Km 235, CEP-13565-905, São Carlos, S. P., Brazil
M.R.M.C. Santos Centro de Cieˆncias da Natureza (CCN), Departamento de Química, Universidade Federal do Piauı´ (UFPI), Teresina, PI, Brazil
E.R. Leitea) and E. Longob) Laborato´rio Interdisciplinar de Eletroquı´mica e Ceraˆmica (LIEC), Centro Multidisciplinar Para Desenvolvimento de Materiais Ceraˆmicos (CMDMC), Departamento de Química, Universidade Federal de Sa˜o Carlos (UFSCar), Via Washington, Km 235, CP-676, CEP-13565-905, São Carlos, S. P., Brazil
F. Lanciotti, Jr. and T.M. Boschi Departamento de Física, Universidade Federal de Sa˜o Carlos (UFSCar), Via Washington, Km 235, CEP-13565-905, São Carlos, S. P., Brazil
J.A. Varela Instituto de Química, Universidade Estadual Paulista (UNESP), Araraquara, S. P., Brazil (Received 27 July 2002; accepted 13 December 2002)
Strontium-modified lead titanate thin films with composition Pb1−xSrxTiO3 were grown on Pt/Ti/SiO2/Si substrates using the polymeric precursor method. The structural phase evolution as a function of the Sr contents was studied using micro-Raman scattering, specular reflectance infrared Fourier transform spectroscopy, and x-ray diffraction. The results showed a gradual change from tetragonal to cubic structure, the transition occurring at about x ⳱ 0.58. The infrared reflectance spectra showed that the frequency of several peaks decreases as the strontium concentration increases. These features are correlated with a decrease in the tetragonal distortion of the TiO6 octahedra as the strontium concentration increases.
I. INTRODUCTION
Intensive research has been focused on ferroelectrics thin films in the last decade with particular emphasis on new processing and characterization techniques.1,2 A considerable amount of research has been developed for a) b)
e-mail: [email protected] Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 18, No. 3, Mar 2003
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thin films because of their potential applications in the field of microelectronic and optoelectronic devices.3,4 Among the ferroelectric thin films, PbTiO3 has received special attention in recent years due to its applications such as pyroelectric infrared detectors, piezoelectric sensors, optical switches, and dynamic random-access memory (DRAM) and nonvolatile ferroelectric randomaccess memory (NVFRAM) devices.5–7 On the other hand, pure PbTiO3 has a large tetragonal distortion at room temperature, approximately 1.064, which introduces © 20
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