Structural and Optical Properties of PbTiO3 Grown on SrTiO3 Substrates by Peroxide MBE
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0966-T07-04
Structural and Optical Properties of PbTiO3 Grown on SrTiO3 Substrates by Peroxide MBE Natalia Izyumskaya1, Vitaliy Avrutin1, Xing Gu1, Umit Ozgur1, Tae Dong Kang2, Hosun Lee2, David John Smith3, and Hadis Morkoc1 1 Department of Electrical and Computer Engineering, Virginia Commonwealth University, 601 West Main St., Richmond, VA, 23284 2 Deptartment of Physics, Kyung Hee University, Yong-In 446-701, Kyung Hee, Korea, Republic of 3 Deptartment of Physics, Arizona State University, A213 Mail code: 1704, Tempe, AZ, 85287 ABSTRACT Single-crystal PbTiO3 layers were grown on (001) SrTiO3 substrates by molecular beam epitaxy using hydrogen peroxide as an oxidant. Phase composition and structural properties of the films were examined as a function of growth parameters. It was found that single-phase PbTiO3 films grew epitaxially at substrate temperatures of 600°C and higher, whereas layers grown at lower temperature contained PbO inclusions. The epitaxial relationship between the films and the substrates was (001)PbTiO3//(001)SrTiO3 and PbTiO3[100]//SrTiO3[100]. No evidence of a-domains was found. Full widths at half maximum of (001) PbTiO3 rocking curves were as low as 6-8 arcmin for 50-60 nm thick films, indicating high crystal quality of the films. From ellipsometric measurements, refractive index and band gap of PbTiO3 were found to be 2.66 at 633 nm and 3.8 eV, respectively. INTRODUCTION Lead titanate (PbTiO3), a ferroelectric material with perovskite structure, has received a great deal of attention owing to a unique combination of its piezoelectric, pyroelectric, dielectric, electo- and acousto-optic properties [1]. PbTiO3 is a very attractive material for use in a wide variety of fields, including ultrasonic sensors, infrared detectors, electro-optic modulators, and ferroelectric random access memories. To harness the intrinsic properties of PbTiO3 for device applications, however, highquality epitaxial films are required. PbTiO3 thin films have been prepared by various methods such as metal organic chemical vapor deposition (MOCVD) [2], rf magnetron sputtering [3], pulsed laser deposition [4], hydrothermal method [5], and sol-gel technique [6]. Surprisingly, molecular beam epitaxy (MBE), a modern growth technique providing high crystal perfection and precise control over material composition, has not been widely applied, except of a few reports involving ozone as an oxidizing agent [7,8]. In this contribution, we report the growth of high-quality single-crystal PbTiO3 layers on (001) SrTiO3 substrates by MBE utilizing hydrogen peroxide as an oxidant, initially developed for ZnO [9]. EXPERIMENTAL DETAILS PbTiO3 layers were grown on (001) SrTiO3 substrates in a Riber 3200 MBE system. The chamber was evacuated by a 1200 l/s turbo pump to a base pressure of 10-8 Torr. Lead (6N purity) and titanium (6N purity) were supplied from double-zone and
high-temperature effusion cells, respectively. A 50% aqueous solution of hydrogen peroxide was used as a source of reactive oxygen [9]. A jet of H2O2/H2O vapor w
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