| Summary: | 碩士 === 東海大學 === 應用物理學系 === 103 === In this present work, BiFeO3 (BFO)thin films with 200 nm in thickness were deposited on both glass and SiO2/Si(100) substrates by rf magnetron sputtering. Structure and ferroelectric properties of BFO films with different underlayers have been investigated. The experimental results show that the pervoskite sturcture BFO phase with preferred (110) orientation is found for BFO on CoPt underlayer at growth temperature (Tg) = 450-550 oC. With the increment of the growth temperature, the grain size is also increased significantly, from 51 nm at Tg = 450 oC to 119 nm at Tg = 550 oC. Ferroelectric behavior is found for BFO at Tg = 450-550 oC, where better ferroelectric properties of 2Pr = 155 μC/cm2 and EC = 362 kV/cm is obtained for BFO films at Tg = 525 oC on glass substrates; and 2Pr = 158 μC/cm2 and EC = 465 kV/cm is obtained for BFO films at Tg = 525 oC on SiO2/Si(100) substrates, respectively. Besides, on CoPt/Ta bilayer undrelayer, the pervoskite sturcture BFO phase with preferred (111) orientation is found for BFO films at Tg = 450-550 oC, but isotropic orientation is preferred at higher Tg = 550 oC. With the increment of the growth temperature, the grain size increased significantly. Ferroelectric behavior is found for BFO at Tg = 450-550 oC, where better ferroelectric properties of 2Pr = 180 μC/cm2 and EC = 343 kV/cm is obtained for BFO films at Tg = 500 oC on glass substrates; 2Pr = 154 μC/cm2 and EC = 341 kV/cm is obtained for BFO films at Tg = 500 oC on SiO2/Si(100) substrates.
Furthermore on CoPt/Pt/Ta trilayer undrelayer, pervoskite sturcture BFO phase higly preferntial (111) orientation with LOF(111) of near 1 is attained for BFO films at Tg = 400-525 oC. With the increment of the growth temperature, the grain size also increased significantly. Ferroelectric behavior is found for BFO at Tg = 400-550 oC, where the optional ferroelectric properties of 2Pr = 221 μC/cm2 and EC = 392 kV/cm is obtained for BFO films at Tg = 550 oC on glass substrates; 2Pr = 204 μC/cm2 and EC = 392 kV/cm is obtained for BFO films at Tg = 550 oC on SiO2/Si(100) substrates. In this study, BFO films on refined CoPt butten electrodes exhibit comparable those ferroelectric properties to those on single crystal oxide substrates.The experiment results suggest that the modification of CoPt underlayer strongly affect the texture of the BFO films, and thus ferroelectric properties.
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