Study on preparing PLT(28) thin film and its electro-optic effect
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Study on preparing PLT(28) thin film and its electro-optic effect Ai-Li Ding, Wei-Gen Luo, P. S. Qiu, J. W. Feng, and R. T. Zhang Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China (Received 26 July 1996; accepted 30 June 1997)
PLT(28) thin films deposited on glass substrates were studied by two sputtering processes. One is an in situ magnetron sputtering and the other is a low-temperature magnetron sputtering. The sintered PLT ceramic powders are used as a sputtering target for both processes. The influences of sputtering and annealing conditions on structure and crystallinity of the films were investigated. The electro-optic (E-O) properties of PLT(28) thin films prepared by the two processes were determined by a technique according to Faraday effect. The researches showed the E-O properties were strongly affected by the sputtering process. The film with larger grains exhibits stronger E-O effect. The quadratic E-O coefficient of PLT(28) thin film varies in the range of 0.1 3 10216 to 1.0 3 10216 (myv)2 .
I. INTRODUCTION
PZT doped with different La contents exhibits many interesting properties, such as ferroelectricity, piezoelectricity, pyroelectricity, and electro-optic (E-O) effects that have been widely used in many devices.1,2 Recently, most of the applications occupied by PZT-type ceramics in bulk are now being replaced by thin film due to the unique features: fast response speed, low drive power, and an accessible large area. The film has especially great potential applications in integrated electronic and electro devices. (28/0/100)PLZT [abbreviated as PLT(28)] thin film is one of the most interesting candidate materials for many electro-optic devices due to their large E-O effect, such as in optical shutter, spatial light modulator, integrated optical waveguides, and so on. There are several methods that can be used to fabricate PLT(28) thin film.3–5 In this paper, two kinds of sputtering process were described which have been successfully used to prepare the perovskite PLT(28) thin films on glass substrates. One is the in situ sputtering process named as method A. In method B, the amorphous films were sputtered at lower substrate temperature and then sequentially annealed to realize the phase conver-
sion from amorphous to perovskite phase state. The transparent PLT(28) films with a perovskite structure can be obtained using both A and B. The influences of sputtering and annealing parameters on the morphology and microstructure of PLT(28) films were investigated. The relationship between annealing process and the formation of the perovskite phase was also reported in this work. The birefringence shift of the films under an applied electric field was determined. Results show
TABLE I. Sputtering conditions. Process Target Target-substrate distance Substrate RF power density Sputtering gas Sputtering pressure Substrate temperature
A
B
PLT(28) Powder, F75 mm 22 – 25 mm
PLT(28) Powder, F150 mm 40 mm
Glass (95% silica) 1.3
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