摘要:
六方YMnO3是一种特殊的多铁性材料,因其具有介电常数低、单一极化轴、无挥发性元素等特点,在磁电领域具有独特的优势,但目前关于YMnO3薄膜的铁电性特别是畴结构的研究相对较少.本文采用溶胶-凝胶法在Si(100)基片上制备了多铁性YMnO3薄膜,利用掠入射X-射线衍射、原子力显微镜对薄膜的结构及表面形貌进行了分析,用压力显微镜(PFM)技术研究了纳米尺度畴结构及微区电滞行为,并通过I-V , P-E曲线进一步研究了薄膜的漏电流和宏观电滞行为.结果表明,该薄膜为六方钙钛矿结构, YMnO3晶粒大小均匀并且结晶性较好,薄膜表面粗糙度为7.209 nm. PFM图显示出清晰的电畴结构,结合典型的微区振幅蝴蝶曲线和相位电滞回线,证实该YMnO3薄膜具有较好的铁电性.由于受内建电场的作用,振幅曲线和相位曲线都向正向偏移,表现出非对称特征.该薄膜的漏电流密度低于10-6 A·cm-2,因而其电滞回线基本能够达到饱和.
Abstract:
Hexagonal YMnO3 is a special kind of multiferroics which shows unique advantages in magneto-electric field due to its low permittivity and only c-axis polarization. However, its ferroelectric properties, especially domain structures, have not been intensively investigated. In this study, YMnO3 film about 270 nm in thickness is prepared on Si(100) substrate by sol-gel spin coating. Structure and morphology of the film are characterized by grazing incidence X-ray diffraction and atomic force microscopy. Domain structure and its reversal behavior on a nanoscale are examined by piezoresponse force microscopy (PFM). The leakage current and ferroelectric property are also investigated. The results show that the film displays a hexagonal perovskite structure with good crystallinity and has smooth surface with a root-mean-square roughness of 7.209 nm. PFM images and typical local piezoresponse loops reveal the good piezoelectric and ferroelectric properties of the YMnO3 film at room temperature. Meanwhile, the offsets of amplitude loop and phase loop are observed due to the internal electric field. Leakage current density of YMnO3 film is lower than 10-6 A·cm-2, so saturated hysteresis loop can be obtained.
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