通过铁电氧化物对CuInP$_2$S$_6$的铁电性和四阱态进行界面调控
Interface-tuning of ferroelectricity and quadruple-well state in CuInP$_2$S$_6$ via ferroelectric oxide
AI总结：
本文提出利用铁电氧化物PbZr$_{0.2}$Ti$_{0.8}$O$_3$界面调控CuInP$_2$S$_6$，克服其低居里温度和畴控制难题，显著增强超薄极限下的铁电性、压电性和极性排列，为柔性纳米器件应用提供有效策略。
摘要：
铁电范德华材料CuInP$_2$S$_6$具有引人入胜的四阱态和负压电性。其技术应用因相对较低的居里温度（块体$T_C$约42 °C）及缺乏精确的畴控制而受阻。本文表明，CuInP$_2$S$_6$可免受尺寸效应影响，且在与铁电氧化物PbZr$_{0.2}$Ti$_{0.8}$O$_3$薄膜界面接触时，在超薄极限下表现出增强的铁电性、压电性和极性排列。压电响应力显微镜研究表明，薄层CuInP$_2$S$_6$的极性畴完全顺应底层PbZr$_{0.2}$Ti$_{0.8}$O$_3$的极性畴，其中压电系数随厚度减小而变号并急剧增大。高温原位畴成像显示，在PbZr$_{0.2}$Ti$_{0.8}$O$_3$上13 nm厚的CuInP$_2$S$_6$的$T_C$显著增强，超过200 °C。密度泛函理论建模和蒙特卡洛模拟表明，增强的极性排列和$T_C$可归因于CuInP$_2$S$_6$中界面介导的结构畸变。本研究为调控CuInP$_2$S$_6$的极性特性提供了一种有效的材料策略，适用于柔性纳米电子学、光电子学和力学应用。
英文摘要：
Ferroelectric van der Waals CuInP$_2$S$_6$ possesses intriguing quadruple-well states and negative piezoelectricity. Its technological implementation has been impeded by the relatively low Curie temperature (bulk $T_C$ ~42 °C) and the lack of precise domain control. Here we show that CuInP$_2$S$_6$ can be immune to the finite size effect and exhibits enhanced ferroelectricity, piezoelectricity, and polar alignment in the ultrathin limit when interfaced with ferroelectric oxide PbZr$_{0.2}$Ti$_{0.8}$O$_3$ films. Piezoresponse force microscopy studies reveal that the polar domains in thin CuInP$_2$S$_6$ fully conform to those of underlying PbZr$_{0.2}$Ti$_{0.8}$O$_3$, where the piezoelectric coefficient changes sign and increases sharply with reducing thickness. High temperature $in$ $situ$ domain imaging points to a significantly enhanced $T_C$ exceeding 200 °C for 13 nm CuInP$_2$S$_6$ on PbZr$_{0.2}$Ti$_{0.8}$O$_3$. Density functional theory modeling and Monte Carlo simulations show that the enhanced polar alignment and $T_C$ can be attributed to interface-mediated structure distortion in CuInP$_2$S$_6$. Our study provides an effective material strategy to engineer the polar properties of CuInP$_2$S$_6$ for flexible nanoelectronic, optoelectronic, and mechanical applications.
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