Atomically thin layers of group VB transition metal dichalcogenides (TMDs) provide a unique platform for studying two-dimensional (2D) superconductivity and charge density waves. Thus far, the bottom-up synthesis of these 2D TMDs has often involved precursors that are corrosive or toxic, and their lateral sizes are typically only a few micrometers. In this paper, we report the growth of NbS₂ nanoflakes with a thickness down to bilayers and a lateral dimension up to tens of micrometers without using harsh chemical species. NbS₂ nanoflakes either standing or lying with respect to the sapphire substrate were obtained by sulfurization of niobium oxide films that were prepared via pulsed laser deposition. Standing nanoflakes are considered to grow epitaxially on the sapphire substrate according to their ordered orientation, while lying nanoflakes with random orientations were grown directly on top of the niobium oxide films. The Raman spectra of the 3R-phase exhibit strong dependence on the layer thickness, where the A₁ mode softens as the layer number decreases. In contrast to the stable bulk NbS₂, the ultra-thin nanoflakes were oxidized on their top surfaces after prolonged exposure to air, as revealed by X-ray photoelectron spectroscopy. Our work explores an important route to synthesize large-size NbS₂ nanoflakes and studies the oxidation process, which is a critical factor to consider if practical applications should be realized in the future.

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VB族过渡金属二硫化碳（TMD）的原子薄层为研究二维（2D）超导性和电荷密度波提供了独特的平台。到目前为止，这些2D TMD的自下而上的合成通常涉及腐蚀性或有毒的前体，并且其横向尺寸通常仅为几微米。在本文中，我们报告了在不使用刺激性化学物质的情况下，NbS ₂纳米薄片的生长厚度可降至双层，横向尺寸可达数十微米。NbS ₂通过硫化通过脉冲激光沉积制备的氧化铌膜，获得了相对于蓝宝石衬底直立或平躺的纳米薄片。直立的纳米薄片被认为是根据其有序取向在蓝宝石衬底上外延生长的，而随机取向的纳米薄片则直接在氧化铌膜的顶部生长。3R相的拉曼光谱表现出对层厚度的强烈依赖性，其中A ₁模式随着层数的减少而软化。X射线光电子能谱显示，与稳定的块状NbS _2相比，超薄纳米片在长时间暴露于空气后会在其顶表面上被氧化。我们的工作探索了合成大型NbS的重要途径₂纳米薄片并研究了氧化过程，这是考虑将来是否应实现实际应用的关键因素。

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