Influence of Crystal Phase and Orientation on Electrooptic Effect of PLZT Epitaxial Films
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0902-T04-08.1
Influence of Crystal Phase and Orientation on Electrooptic Effect of PLZT Epitaxial Films 1,2, 3 1,2,3, Keisuke Sato , Masatoshi Ishii Masao Kondo1 and Kazuaki Kurihara1 1 Fujitsu Laboratories Limited, 10-1 Morinosato-Wakamiya, Atsugi 243-0197, Japan 2 Fujitsu Ltd. 4-1-1 Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa 211-8588 Japan 3 OITDA. 1-20-10 Sekiguchi, Bunkyo-ku, Tokyo 112-0014 Japan ABSTRACT Lanthanum-modified lead zirconate titanate and lead zirconate titanate epitaxial films with (100) and (111) orientations are grown respectively on (100) and (111) niobium, lending conductivity to strontium titanate through chemical solution deposition. This study investigates changes in the ordinary and extraordinary refractive index no and ne induced in these films by an electric field using the prism-coupling method. Anisotropic electrooptic effects arise from the Pockels effect and switching among polar clusters. Isotropic electrooptic effect is realized on PLZT 8/65/35 and PZT 70/30 of (100) epitaxial films. INTRODUCTION Lanthanum-modified lead zirconate titanate ((Pb1-xLax) (ZryTi1-y) O3 [hereafter referred to as PLZT (X/Y/100-Y), where X=100x, Y=100y)], is of great interest in electrooptic applications because of its large electrooptic coefficient [1, 2]. Numerous applications, such as optical shutters [3], modulators [4], and switches [5] have been proposed using this material. The range of the most extensively studied composition is PLZT X/65/35 (X=4-14). Bulk ceramics with these compositions exhibit properties of ferroelectric relaxors, such as dielectric responses that have frequency dependence, a lack of macrosymmetry changes near the dielectric peak, and a narrow polarization loop versus an electric field. Temperature dependence of the refractive index has also been reported [6]. A sharp reduction in the refractive index is apparent below the Burns temperature, Td, of 627 K in X=65=35 (X = 4-14). This refractive index anomaly is attributed to the formation of local polar clusters below Td. Viehland et al. [7] have investigated transmission electron microscopy, and polar clusters have been observed in PLZT X/65/35 (X ≥ 8). Transparent PLZT bulk ceramics are investigated in this study to clarify the origin of the large electrooptic effect. A large electrooptic coefficient (rc =500 pm/V) is reported in bulk PLZT ceramics [1]. Regarding the measurement of clamped and unclamped bulk PLZT ceramics, the electrooptic coefficient of the clamped PLZT ceramic is smaller than that of the unclamped one [8].
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Electrooptic constants are defined by the following equations. ∆n33= – (n33)3 r33 E /2 ∆n13= – (n13)3 r13 E /2 rc = r33 – (n13/n33)3 r13 In those equations, E is the electric field; and n33 and n13 respectively denote the extraordinary (ne) and ordinary (no) refractive indices. Previous studies of the electrooptic effect of PLZT thin film have undertaken measurements using ellipsometric techniques. These techniques measure changes in the material birefringence [9, 10]. Potter et al. indiv
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