Zhu Weiguang, Zhang Yanming, Shen Junhua, Shi Yunfeng, Li Mingxin, Lian Jie
Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States.
Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States.
ACS Nano. 2022 Jul 5. doi: 10.1021/acsnano.1c07662.
Manipulating materials at the atomic scale and assembling them into macroscopic structures with controlled dimensionalities and single-crystal quality are grand scientific challenges. Here, we report a general solvent evaporation method to synthesize large-area uniaxial-oriented growth of free-standing thin films at the liquid-air interface. Crystals nucleate at the solution surface and rotate into the same orientation under electrostatic interaction and then merge as large crystals and grow laterally into a large-area uniform thin film with millimeter-sized grains. The lateral dimension is confined only by the size of containers. The film thickness can be tuned by adjusting solvent evaporation rate () and solute diffusivity (), and a characteristic length, , was derived to estimate the film thickness. Molecular dynamic (MD) simulations reveal a concentration spike at the liquid-air interface during fast solvent evaporation, leading to the lateral growth of thin films. The large-area uniaxial oriented films are demonstrated on both inorganic metal halides and hybrid metal halide perovskites. The solvent evaporation approach and the determination of key parameters enabling film thickness prediction are beneficial to the high throughput and scalable production of single crystal-quality thin film materials under controlled evaporation conditions.
在原子尺度上操控材料并将它们组装成具有可控维度和单晶质量的宏观结构是重大的科学挑战。在此，我们报道了一种通用的溶剂蒸发方法，用于在液 - 气界面合成大面积单轴取向生长的独立薄膜。晶体在溶液表面成核，并在静电相互作用下旋转至相同取向，然后合并成大晶体，并横向生长成具有毫米级晶粒的大面积均匀薄膜。横向尺寸仅受容器大小限制。薄膜厚度可通过调节溶剂蒸发速率（）和溶质扩散率（）来调整，并且推导出一个特征长度（）来估计薄膜厚度。分子动力学（MD）模拟揭示了在快速溶剂蒸发过程中液 - 气界面处的浓度峰值，这导致了薄膜的横向生长。在无机金属卤化物和混合金属卤化物钙钛矿上都展示了大面积单轴取向薄膜。这种溶剂蒸发方法以及能够预测薄膜厚度的关键参数的确定，有利于在可控蒸发条件下高通量且可扩展地生产单晶质量的薄膜材料。
