Thickness-dependent crystal structure and electric properties of epitaxial ferroelectric Y2O3-HfO2 films
Thickness-dependent crystal structure and electric properties of epitaxial ferroelectric Y2O3-HfO2 films
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DOI：
10.1063/1.5040018
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发表时间：
2018-09
影响因子：
4
通讯作者：
T. Mimura;Takao Shimizu;H. Uchida;O. Sakata;H. Funakubo
中科院分区：
文献类型：
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作者：
T. Mimura;Takao Shimizu;H. Uchida;O. Sakata;H. Funakubo
研究了(111)取向外延0.07YO1.5-0.93HfO2(YHO7)铁电薄膜在10-115 nm厚度范围内的晶体结构和电学性质与厚度的关系。采用脉冲激光沉积或溅射的方法在室温下制备了YHO7薄膜，并对其进行了热处理。作为外延生长YHO7薄膜的衬底，使用了(111)取向的10wt.%锡掺杂的In_2O_3(ITO)//(111)Y_2O_3稳定的氧化锆。X-射线衍射仪证实，对于厚达115 nm的薄膜，其主晶相为铁电正交晶相。薄膜的剩余极化(Pr)和饱和极化(Ps)随膜厚变化较小。矫顽场(EC)的厚度依赖性也很小，这一行为与传统的铁电薄膜如Pb(Zr，Ti)O_3不同。此外，无取向多晶YHO7薄膜具有与外延YHO7薄膜相似的厚度依赖关系和几乎相同的EC值。我们认为，无论是对于外延薄膜还是多晶薄膜，铁电区域都非常小。即使在较厚的薄膜中，这种小的磁区仍然存在，从而产生与厚度无关的EC。
The thickness dependences of the crystal structure and electric properties of (111)-oriented epitaxial 0.07YO1.5-0.93HfO2 (YHO7) ferroelectric films were investigated for the film thickness range of 10–115 nm. The YHO7 films were grown by pulsed laser deposition or sputtering at room temperature and subsequent heat treatment. As a substrate for the epitaxial growth of the YHO7 film, (111)-oriented 10 wt. % Sn-doped In2O3(ITO)//(111) yttria-stabilized zirconia was used. X-ray diffraction measurements confirmed that the main crystal phase of these YHO7 films was ferroelectric orthorhombic for up to 115-nm-thick films. Small film-thickness dependences of remanent polarization (Pr) and saturation polarization (Ps) were observed. Thickness dependence of the coercive field (Ec) is also small, and this behavior does not resemble that of conventional ferroelectric films such as Pb(Zr,Ti)O3. Additionally, non-oriented polycrystalline YHO7 films are reported to have similar thickness dependence of Ec and almost the same Ec value to epitaxial YHO7 films. We suggest that the ferroelectric domain is significantly small for both epitaxial and polycrystalline films. Such small domains remain even in thicker films, giving rise to thickness-independent Ec.