Multi-step chemical vapor deposition (CVD) is a synthesis method which is capable of producing a uniform, large area, and high-quality thin films. In this work, we report the effect of post-annealing on the structural and optical properties of few-layers (FL) MoS₂ thin films synthesized by multi-step CVD. Based on atomic force microscopic image, the thickness of the MoS₂ thin film is ∼3 nm, which is equivalent to five layers. After annealing at 900°C for 17 min, intensity of the A_1g and ${\text{E}}_{2\text{g}}^1$full-width-at-half-maximum (FWHM) Raman modes increased by ∼3 times while the reduced from ∼10 cm⁻¹ to ∼7.5 cm⁻¹ for A_1g and from ∼13.6 cm⁻¹ to ∼7.5 cm⁻¹ for ${\text{E}}_{2\text{g}}^1$. Both of the as-grown and annealed samples showed X-ray (002) diffraction peak at 14.2° but the intensity was more prominent for the annealed sample. It was found that the annealed sample showed clear and distinct absorbance peaks at 666, 615, 448, 401, and 278 nm which correspond to the A, B, C, D, and E excitons, respectively. The results indicate that annealing significantly improved the optical and structural quality of the MoS₂ film. Field-effect transistor based on annealed MoS₂ thin film was fabricated and showed electron mobility of 0.21 cm²V⁻¹s⁻¹, on/off ratio of 1.3 × 10² and a threshold voltage of 0.72 V. Our work highlights the importance of high-temperature annealing in multi-step CVD to obtain a uniform and high-quality FL MoS₂ thin films.

多步化学气相沉积（CVD）是一种能够生产均匀，大面积和高质量薄膜的合成方法。在这项工作中，我们报告了后退火对通过多步CVD合成的几层（FL）MoS ₂薄膜的结构和光学性质的影响。根据原子力显微镜图像，MoS ₂薄膜的厚度约为3 nm，相当于五层。在900°C退火17分钟后，A _1g的强度和${\text{Ë}}_{2\text{G}}^{\mathrm{1个}}$半最大全宽（FWHM）拉曼模式增加了约3倍，而A _1g的拉曼模式则从约10 cm ^-1减小到7.5 cm ^-1，从13.6 cm ^-1减小到7.5 cm ^-1对于${\text{Ë}}_{2\text{G}}^{\mathrm{1个}}$。刚生长和退火的样品均在14.2°处显示X射线（002）衍射峰，但退火后的样品强度更高。发现退火后的样品在666、615、448、401和278 nm处分别显示出清晰，独特的吸收峰，分别对应于A，B，C，D和E激子。结果表明，退火显着改善了MoS ₂薄膜的光学和结构质量。制造了基于退火的MoS ₂薄膜的场效应晶体管，该晶体管的电子迁移率为0.21 cm ² V ^-1 s ^-1，开/关比为1.3×10 ²阈值电压为0.72V。我们的工作突出了在多步CVD中进行高温退火以获得均匀且高质量的FL MoS ₂薄膜的重要性。