Abdeldayem Mohamed, Liu Chang-Ming, Shah Izaz-Ali, Fiedler Andreas, Klimm Detlef, Albrecht Martin, Schwarzkopf Jutta
Leibniz-Institut für Kristallzüchtung, Max-Born-Straße 2, Berlin 12489, Germany.
Cryst Growth Des. 2025 May 23;25(11):3654-3664. doi: 10.1021/acs.cgd.4c01412. eCollection 2025 Jun 4.
Calcium titanate thin films with high structural quality were grown heteroepitaxially on perovskite oxide substrates using the liquid-delivery spin metal-organic vapor phase epitaxy (MOVPE) technique. To determine the growth window, suitable metal-organic precursors were selected, and their evaporation conditions were established. Initially, the thermal decomposition behavior of the precursors was studied using thermogravimetric analysis, which showed that full pyrolysis at 460 °C is possible for both the Ca and Ti precursors. This enabled the growth of fully strained, stoichiometric CaTiO films on SrTiO and NdGaO substrates, and potentially on other perovskite oxide substrates, within the diffusion-limited regime. The influence of vaporization temperatures, substrate temperature, oxygen-to-argon ratio, and Ca-to-Ti ratio on the structural properties of the CaTiO thin films was investigated using high-resolution X-ray diffraction, atomic force microscopy, and transmission electron microscopy. Structural analysis was ultimately correlated with electrical properties measured via IV curves. Intrinsic resistive switching was observed for stoichiometric and slightly off-stoichiometric CaTiO films grown on SrTiO substrates with ≈2.2% tensile strain. Relative to our previous work on resistive switching in SrTiO (Baki., Sci. Rep., 2021, 11 (1), 1-11), the underlying mechanism is discussed in the context of CaTiO. This highlights the potential of CaTiO for technological applications such as resistive random-access memory (ReRAM) and neuromorphic computing.
采用液体输送旋转金属有机气相外延（MOVPE）技术，在钙钛矿氧化物衬底上异质外延生长了具有高结构质量的钛酸钙薄膜。为了确定生长窗口，选择了合适的金属有机前驱体，并确定了它们的蒸发条件。最初，使用热重分析研究了前驱体的热分解行为，结果表明，钙和钛前驱体在460℃时都有可能完全热解。这使得在扩散限制区域内，能够在SrTiO₃和NdGaO₃衬底上，以及潜在地在其他钙钛矿氧化物衬底上生长完全应变的化学计量比CaTiO₃薄膜。使用高分辨率X射线衍射、原子力显微镜和透射电子显微镜研究了蒸发温度、衬底温度、氧氩比和钙钛比对CaTiO₃薄膜结构性能的影响。最终将结构分析与通过IV曲线测量的电学性能相关联。在具有约2.2%拉伸应变的SrTiO₃衬底上生长的化学计量比和略微偏离化学计量比的CaTiO₃薄膜中观察到了本征电阻开关现象。相对于我们之前关于SrTiO₃中电阻开关的工作（Baki., Sci. Rep., 2021, 11 (1), 1 - 11），在CaTiO₃的背景下讨论了其潜在机制。这突出了CaTiO₃在电阻随机存取存储器（ReRAM）和神经形态计算等技术应用中的潜力。
