The conversion of chalcogen atoms to other types in transition metal dichalcogenides has significant advantages for tuning bandgaps and constructing in-plane heterojunctions; however, difficulty arises from the conversion of sulfur or selenium to tellurium atoms owing to the low decomposition temperature of tellurides. Here, we propose the use of sodium for converting monolayer molybdenum disulfide (MoS2) to molybdenum ditelluride (MoTe2) under Te-rich vapors. Sodium easily anchors tellurium and reduces the exchange barrier energy by scooting the tellurium to replace sulfur. The conversion was initiated at the edges and grain boundaries of MoS2, followed by complete conversion in the entire region. By controlling sodium concentration and reaction temperature of monolayer MoS2, we tailored various phases such as semiconducting 2H-MoTe2, metallic 1T′-MoTe2, and 2H-MoS2?x Te x alloys. This concept was further extended to WS2. A high valley polarization of ~37% in circularly polarized photoluminescence was obtained in the monolayer WS2?x Te x alloy at room temperature.
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机译：硫属元素原子在过渡金属二卤化硅中的转化为其他类型，对于调节带隙和构建面内异质结具有明显的优势。但是，由于碲化物的分解温度低，因此难以将硫或硒转化为碲原子。在这里，我们建议使用钠在富含Te的蒸气下将单层二硫化钼（MoS2）转化为二碲化钼（MoTe2）。钠很容易锚固碲，并通过踩踏碲代替硫来降低交换势垒能量。在MoS2的边缘和晶界处开始转换，然后在整个区域中完成转换。通过控制钠浓度和单层MoS2的反应温度，我们定制了各种相，例如半导体2H-MoTe2，金属1T'-MoTe2和2H-MoS2？x Te x合金。这个概念进一步扩展到了WS2。在室温下，单层WS2ΔxTe x合金在圆偏振光致发光中获得约37％的高谷底偏振。
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