Two-dimensional (2D) materials have drawn ever-increasing interest for the application of surface-enhanced Raman scattering (SERS) because of their low-cost synthesis, non-toxic characteristics, flat surface and outstanding optical properties. The unique thickness-dependent SERS of 2D materials is intriguing, however, the underlying mechanism of this phenomenon is not fully understood. In this work, the few-layer platinum telluride (PtTe₂), an emerging 2D type-II Dirac semimetal with strong interlayer interaction, is explored as a potential SERS substrate. The Raman enhancement on 2D PtTe₂ is confirmed experimentally to be originated from the predominant charge transfer mechanism. The unique thickness-dependent SERS effect reveals that four-layer (4 L) PtTe₂ exhibits the strongest Raman intensity of probe molecule Rhodamine 6 G (R6G). Combined with the theoretical investigation by density functional theory (DFT), the ultrasensitive SERS effect of 4 L PtTe₂ is found to be attributed to its high density of states (DOS) near the Fermi level and strongest built-in electric field at the interface of molecule/PtTe₂. R6G, crystal violet (CV) and rhodamine B (RhB) on 4 L PtTe₂ all reach a detection limit as low as 10⁻¹⁰ M. The uniformity, stability and photobleaching effect of PtTe₂ as SERS substrate is also studied. Our findings reveal that the charge transfer between molecule and 2D materials is a complex process that is influenced by multiple factors, which might deepen our understanding of the unique chemical mechanism (CM) of SERS in 2D materials.

二维 (2D) 材料由于其合成成本低、无毒、表面平整和出色的光学性能，在表面增强拉曼散射 (SERS) 应用中引起了越来越多的兴趣。二维材料独特的依赖于厚度的 SERS 很有趣，但是，这种现象的潜在机制尚不完全清楚。在这项工作中，研究了多层碲化铂 (PtTe ₂ )，一种新兴的具有强层间相互作用的二维 II 型狄拉克半金属，作为潜在的 SERS 衬底进行了探索。_{2D PtTe 2}上的拉曼增强通过实验证实源自主要的电荷转移机制。独特的依赖于厚度的 SERS 效应揭示了四层 (4 L) PtTe ₂表现出探针分子罗丹明 6 G (R6G) 的最强拉曼强度。结合密度泛函理论（DFT）的理论研究，发现4 L PtTe ₂的超灵敏SERS效应归因于其在费米能级附近的高态密度（DOS）和界面处最强的内建电场分子/PtTe ₂。R6G、结晶紫（CV）和罗丹明B（RhB）在4 L PtTe ₂上均达到低至10 ^-10 M的检测限。PtTe _{2的均匀性、稳定性和光漂白效果}作为 SERS 基板也进行了研究。我们的研究结果表明，分子和二维材料之间的电荷转移是一个受多种因素影响的复杂过程，这可能会加深我们对二维材料中 SERS 独特化学机制 (CM) 的理解。