Abstract Molybdenum disulfide (MoS2) is one of the most interesting 2D materials. However, while monolayer MoS2 is well-explored, the few-layer flakes, also promising for flexible device and nano-optoelectronics application, remain less investigated. We study the variation of exciton and trion photoluminescence (PL) and structural properties of few-layer MoS2 grown on SiO2/Si by chemical vapor deposition. Scanning electron and atomic force microscopies show that most of the flakes have a triangular shape. The µ-PL spectra of the flakes show two broad bands associated to the A exciton overlapped by trion and B exciton. The light emission at room temperature redshifts when the number of layers increases, controlled by µ-Raman spectroscopy. In the temperature-dependent measurements from 80 to 290 K, the PL redshifts according to bandgap narrowing, while the intensity decreases due to the thermally activated nonradiative recombination related to the increase of the electron-phonon interaction. Exciton and trion bands are deconvoluted and their behaviors with temperature are studied by fitting the PL data with modelling equations. This allows to evaluate the spin-orbit splitting, quenching activation energy, trion effective size and other important parameters. These new findings are useful for the potential applications of few-layer MoS2 in nano-optoelectronics involving external modulation of optical properties.

中文翻译：

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少层 MoS2 中的激子和三离子：厚度和温度相关的光致发光

摘要 二硫化钼（MoS2）是最有趣的二维材料之一。然而，虽然单层 MoS2 得到了很好的探索，但对于柔性器件和纳米光电子应用也很有希望的几层薄片仍然很少被研究。我们研究了激子和三重离子光致发光 (PL) 的变化以及通过化学气相沉积在 SiO2/Si 上生长的少层 MoS2 的结构特性。扫描电子和原子力显微镜显示大部分薄片呈三角形。薄片的 μ-PL 光谱显示了与 A 激子相关的两个宽频带，并被 trion 和 B 激子重叠。当层数增加时，室温下的光发射红移，由 µ-拉曼光谱控制。在 80 到 290 K 的温度相关测量中，PL 根据带隙变窄而红移，而强度由于与电子-声子相互作用增加相关的热激活非辐射复合而降低。通过用建模方程拟合 PL 数据，对激子和三重子带进行解卷积，并研究它们随温度的行为。这允许评估自旋轨道分裂、淬灭活化能、trion 有效尺寸和其他重要参数。这些新发现对于少层二硫化钼在涉及光学特性外部调制的纳米光电子学中的潜在应用很有用。这允许评估自旋轨道分裂、淬灭活化能、trion 有效尺寸和其他重要参数。这些新发现对于少层二硫化钼在涉及光学特性外部调制的纳米光电子学中的潜在应用很有用。这允许评估自旋轨道分裂、淬灭活化能、trion 有效尺寸和其他重要参数。这些新发现对于少层二硫化钼在涉及光学特性外部调制的纳米光电子学中的潜在应用很有用。