Two-dimensional molybdenum disulfide (MoS₂) has recently drawn major attention due to its promising applications in electronics and optoelectronics. Chemical vapor deposition (CVD) is a scalable method to produce large-area MoS₂ monolayers, yet it is challenging to achieve shape-uniform, high-quality monolayered MoS₂ grains as random, diverse crystallographic orientations and various shapes are produced in the same CVD process. Here, we report the growth of high-quality MoS₂ monolayers with uniform triangular shapes dominating (up to 89%) over other shapes on both SiO₂/Si and sapphire substrates. The new confined-space CVD process prevents contamination and helps regulate the Mo/S ratio during the deposition. The as-grown triangular MoS₂ monolayers exhibit grain sizes up to 150 μm and possess better crystalline properties and lighter n-type doping concentration than those of the monolayers grown by common CVD methods. The corresponding field effect transistor devices show high electron mobilities of 50–60 cm² V^–1 s^–1 and positive threshold voltages of 21–35 V. This mild n-type behavior makes it possible to regulate the formation of excitons by back-gate voltage due to the interaction of excitons with free charge carriers in the MoS₂ channel. As a result, gate-tunable photoluminescence (PL) effect, which is rarely achievable for MoS₂ samples prepared by common CVD or mechanical exfoliation, is demonstrated. This study provides a simple versatile approach to fabricating monolayered crystals of MoS₂ and other high-quality transition metal dichalcogenides and could lead to new optoelectronic devices based on gate-tunable PL effect.

中文翻译：

---

形状均匀，高质量的单层MoS ₂晶体，可用于门可调的光致发光

由于二维二硫化钼（MoS ₂）在电子和光电子领域的应用前景广阔，因此最近受到了广泛的关注。化学气相沉积（CVD）是生产大面积MoS ₂单层的可扩展方法，但是要获得形状均匀，高质量的单层MoS ₂晶粒却具有挑战性，因为随机，多样的晶体取向和相同形状都可以产生CVD工艺。在这里，我们报告了在两个SiO ₂上均具有高品质的MoS ₂单层的增长，这些三角形具有均匀的三角形形状（最多达89％），超过其他形状/ Si和蓝宝石衬底。新的密闭空间CVD工艺可防止污染，并有助于在沉积过程中调节Mo / S比。所生长的三角形MoS ₂单层与通过常规CVD方法生长的单层相比，具有最大150μm的晶粒尺寸，并具有更好的结晶特性和更轻的n型掺杂浓度。相应的场效应晶体管器件显示出50–60 cm ² V ^–1 s ^–1的高电子迁移率和21–35 V的正阈值电压。这种温和的n型行为使得可以通过反激来调节激子的形成。 MoS ₂中激子与自由电荷载流子相互作用产生的栅极电压渠道。结果，证明了通过普通CVD或机械剥离法制备的MoS ₂样品极难实现的栅极可调光致发光（PL）效果。这项研究提供了一种简单的通用方法来制造MoS ₂和其他高质量过渡金属二卤化硅的单层晶体，并可能导致基于栅极可调PL效应的新型光电器件。