As for nonlayered 2D polymorphic materials, especially for Cr‐based chalcogenides, large‐area thin film growth with phase control is considered the most important synthesis challenge for magnetic, electronic, and optoelectronic devices. However, the synthesis methods of large continuous thin films for nonlayered 2D materials are still limited and rarely reported, also for the phase control growth, which is inhibited by isotropic 3D growth and similar Gibbs free energy for different phases. Herein, enhanced mass transport chemical vapor deposition is established to achieve the control synthesis of trigonal Cr2S3 thin films, in which the stable boundary layer supplies the continuous reaction species and tunes the reaction kinetics. The trigonal phase formation is confirmed by atomic structure characterization, optical absorption and piezoelectric measurements, demonstrating unique physical properties different from rhombohedral phase. The trigonal Cr2S3 thin films show obvious layer independent and dissimilar angle‐resolved harmonic generation, indicating the surface broken symmetry that can be understood by the combination of negligible piezoelectric response for bulk. The work presents the large‐area synthesized strategy by the modification of mass transport for nonlayered 2D materials with new phase formation and establishes the surface symmetry breaking dominated SHG mechanism for future nonlinear optical materials.

中文翻译：

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通过超低气流控制动态输运相控合成大面积三角二维 Cr2S3 薄膜

对于非层状二维多晶型材料，特别是铬基硫属化物，相控的大面积薄膜生长被认为是磁性、电子和光电器件最重要的合成挑战。然而，非层状 2D 材料的大连续薄膜的合成方法仍然有限且很少报道，对于相控生长也是如此，相控生长受到各向同性 3D 生长和不同相的类似吉布斯自由能的抑制。本文建立了增强传质化学气相沉积来实现三方Cr的控制合成2S3薄膜，其中稳定的边界层提供连续的反应物种并调节反应动力学。通过原子结构表征、光吸收和压电测量证实了三角相的形成，表现出不同于菱面体相的独特物理性质。三角Cr2S3薄膜表现出明显的层无关和不同的角度分辨谐波产生，表明表面对称性破缺，可以通过可忽略的体压电响应的组合来理解。该工作提出了通过修改具有新相形成的非层状二维材料的传质的大面积合成策略，并为未来的非线性光学材料建立了以表面对称性破缺为主的倍频机制。