Kim Bogyu, Jeon Young-Uk, Lee Chulwoo, Kim In Soo, Lee Byeong-Hyeon, Kim Young-Hwan, Kim Young Duck, Han Il Ki, Lee Kwanil, Kim Jongbum, Kang JoonHyun
Nanophotonics Research Center, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea.
KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul, 02447, Republic of Korea.
Sci Rep. 2022 Mar 30;12(1):5363. doi: 10.1038/s41598-022-09182-0.
In this study, we experimentally demonstrate fabrication of ultra-smooth and crystalline barium titanate (BTO) films on magnesium oxide (MgO) substrates by engineering lattice strain and crystal structure via thermal treatment. We observe that oxygen-depleted deposition allows growth of highly strained BTO films on MgO substrates with crack-free surface. In addition, post-thermal treatment relaxes strain, resulting in an enhancement of ferroelectricity. Surface roughening of the BTO films caused by recrystallization during post-thermal treatment is controlled by chemical-mechanical polishing (CMP) to retain their initial ultra-smooth surfaces. From Raman spectroscopy, reciprocal space map (RSM), and capacitance-voltage (C-V) curve measurements, we confirm that the ferroelectricity of BTO films strongly depend on the relaxation of lattice strain and the phase transition from a-axis to c-axis oriented crystal structure.
在本研究中，我们通过热处理工程晶格应变和晶体结构，实验证明了在氧化镁（MgO）衬底上制备超光滑且结晶的钛酸钡（BTO）薄膜。我们观察到，贫氧沉积允许在MgO衬底上生长具有无裂纹表面的高应变BTO薄膜。此外，后热处理可松弛应变，从而增强铁电性。通过化学机械抛光（CMP）控制后热处理过程中再结晶引起的BTO薄膜表面粗糙度，以保持其初始超光滑表面。通过拉曼光谱、倒易空间映射（RSM）和电容-电压（C-V）曲线测量，我们证实BTO薄膜的铁电性强烈依赖于晶格应变的松弛以及从a轴到c轴取向晶体结构的相变。
