Recently, two-dimensional monolayer molybdenum disulfide (MoS2), a transition metal dichalcogenide, has received considerable attention due to its direct bandgap, which does not exist in its bulk form, enabling applications in optoelectronics and also thanks to its enhanced catalytic activity which allows it to be used for energy harvesting. However, growth of controllable and high-quality monolayers is still a matter of research and the parameters determining growth mechanism are not completely clear. In this work, chemical vapor deposition is utilized to grow monolayer MoS2 flakes while deposition duration and temperature effect have been systematically varied to develop a better understanding of the MoS2 film formation and the influence of these parameters on the quality of the monolayer flakes. Different from previous studies, SEM results show that single-layer MoS2 flakes do not necessarily grow flat on the surface, but rather they can stay erect and inclined at different angles on the surface, indicating possible gas-phase reactions allowing for monolayer film formation. We have also revealed that process duration influences the amount of MoO3/MoO2 within the film network. The homogeneity and the number of layers depend on the change in the desorption-adsorption of radicals together with sulfurization rates, and, inasmuch, a careful optimization of parameters is crucial. Therefore, distinct from the general trend of MoS2 monolayer formation, our films are rough and heterogeneous with monolayer MoS2 nanowalls. Despite this roughness and the heterogeneity, we observe a strong photoluminescence located around 675 nm.

中文翻译：

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通过化学气相沉积法生长的单壁 MoS2 单层薄片的研究。

最近，二维单层二硫化钼（MoS2）是一种过渡金属二硫属化物，由于其直接带隙而受到了相当大的关注，而直接带隙在其块体形式中并不存在，使其能够在光电子学中得到应用，而且由于其增强的催化活性，使得它用于能量收集。然而，可控和高质量单层细胞的生长仍然是一个研究问题，决定生长机制的参数尚不完全清楚。在这项工作中，利用化学气相沉积来生长单层 MoS2 薄片，同时系统地改变沉积时间和温度效应，以更好地了解 MoS2 薄膜的形成以及这些参数对单层薄片质量的影响。与之前的研究不同，SEM结果表明，单层MoS2薄片不一定在表面生长平坦，而是可以在表面上保持直立和以不同角度倾斜，这表明可能发生气相反应，从而形成单层薄膜。我们还发现，工艺持续时间会影响薄膜网络中 MoO3/MoO2 的含量。均匀性和层数取决于自由基解吸-吸附的变化以及硫化速率，因此，仔细优化参数至关重要。因此，与MoS2单层形成的总体趋势不同，我们的薄膜是粗糙且异质的，具有单层MoS2纳米墙。尽管存在这种粗糙度和不均匀性，我们仍然观察到位于 675 nm 附近的强光致发光。