Atomically thin two-dimensional (2D) materials face significant energy barriers for synthesis and processing into functional metastable phases such as Janus structures. Here, the controllable implantation of hyperthermal species from pulsed laser deposition (PLD) plasmas is introduced as a top-down method to compositionally engineer 2D monolayers. The kinetic energies of Se clusters impinging on suspended monolayer WS2 crystals were controlled in the <10 eV/atom range with in situ plasma diagnostics to determine the thresholds for selective top layer replacement of sulfur by selenium for the formation of high quality WSSe Janus monolayers at low (300 °C) temperatures and bottom layer replacement for complete conversion to WSe2. Atomic-resolution electron microscopy and spectroscopy in tilted geometry confirm the WSSe Janus monolayer. Molecular dynamics simulations reveal that Se clusters implant to form disordered metastable alloy regions, which then recrystallize to form highly ordered structures, demonstrating low-energy implantation by PLD for the synthesis of 2D Janus layers and alloys of variable composition.

中文翻译：

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低能量注入过渡金属双硫属化物单层以形成Janus结构。

原子薄的二维（2D）材料在合成和加工成功能亚稳相（如Janus结构）时面临着巨大的能量障​​碍。在这里，从自上而下的方法引入了从脉冲激光沉积（PLD）等离子体中可控注入的高温物种，从而对2D单层进行成分工程设计。用原位等离子体诊断法将撞击在悬浮单层WS2晶体上的Se团簇的动能控制在<10 eV /原子范围内，以确定在硒形成的高品质WSSe Janus单层膜上硒选择性置换硫的阈值。低温（300°C）和底层更换，可完全转换为WSe2。倾斜几何形状的原子分辨率电子显微镜和光谱证实了WSSe Janus单层。