Monolayer transition metal dichalcogenides (TMD) have numerous potential applications in ultrathin electronics and photonics. The exposure of TMD-based devices to light generates photo-carriers resulting in an enhanced conductivity, which can be effectively used, e.g., in photodetectors. If the photo-enhanced conductivity persists after removal of the irradiation, the effect is known as persistent photoconductivity (PPC). Here we show that ultraviolet light (λ = 365 nm) exposure induces an extremely long-living giant PPC (GPPC) in monolayer MoS₂ (ML-MoS₂) field-effect transistors (FET) with a time constant of ~30 days. Furthermore, this effect leads to a large enhancement of the conductivity up to a factor of 10⁷. In contrast to previous studies in which the origin of the PPC was attributed to extrinsic reasons such as trapped charges in the substrate or adsorbates, we show that the GPPC arises mainly from the intrinsic properties of ML-MoS₂ such as lattice defects that induce a large number of localized states in the forbidden gap. This finding is supported by a detailed experimental and theoretical study of the electric transport in TMD based FETs as well as by characterization of ML-MoS₂ with scanning tunneling spectroscopy, high-resolution transmission electron microscopy, and photoluminescence measurements. The obtained results provide a basis for the defect-based engineering of the electronic and optical properties of TMDs for device applications.

单层过渡金属二硫化碳（TMD）在超薄电子学和光子学中具有众多潜在应用。基于TMD的设备暴露在光下会产生光载流子，从而导致电导率提高，可以在例如光电探测器中有效使用。如果去除辐射后光增强的电导率仍然存在，则该效应被称为持久光导（PPC）。在这里，我们显示紫外线（λ= 365 nm）暴露在单层MoS ₂（ML-MoS ₂）场效应晶体管（FET）中诱导了一个寿命很长的巨型PPC（GPPC ），其时间常数约为30天。此外，这种作用导致电导率大大提高，最高可达10 ⁷倍。。与以前的研究（其中PPC的起源归因于外部原因，例如被捕获在基质或吸附物中的电荷）相反，我们表明GPPC主要来自ML-MoS ₂的固有特性，例如引起晶格缺陷的晶格缺陷。禁区中存在大量的本地化国家。这一发现得到了基于TMD的FET中电传输的详细实验和理论研究的支持，以及通过扫描隧道光谱，高分辨率透射电子显微镜和光致发光测量对ML-MoS _2的表征。获得的结果为基于TMD的电子和光学特性的基于缺陷的工程设计提供了基础。