It is quite necessary to understand and control the essential carrier dynamic behaviors of two-dimensional WS₂, which is regarded as a very promising material for integrated nanoelectronic and optoelectronic devices. Herein, a high-temperature driven carrier transfer process of multilayer WS₂ nanoflakes is proposed. The established model, involving the inter-valley transfer process of photocarriers from the Λ/Γ point to the K point, predicts the significant emission enhancement of the K → K direct transition at high temperatures, which is verified by both theoretical calculations and experimental observations. On the one hand, variations in the estimated population ratio of photo-carriers with increasing temperature well support the proposed model. On the other hand, temperature-dependent photoluminescence spectra clearly show that the K → K direct emission intensity is remarkably enhanced by ∼300-fold as the temperature is elevated to 760 K. Time-resolved fluorescence spectral studies confirm the occurrence of the inter-valley carrier transfer process in the multilayer WS₂. These results provide solid evidence for the proposed inter-valley carrier transfer model. Such a mechanism could not only be applied to improve the luminescence intensity of indirect-band-gap semiconductors, but also be further extended to design optoelectronic devices which have special requirements on controlling the carrier dynamic behavior.

中文翻译：

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多层WS ₂ †中的高温驱动的谷间载流子转移和显着的荧光增强

非常有必要了解和控制二维WS ₂的基本载流子动态行为，二维WS ₂被认为是用于集成纳米电子和光电器件的非常有前途的材料。在此，提出了多层WS ₂纳米薄片的高温驱动载流子转移过程。建立的模型涉及光载体从Λ / Γ点到K点的谷间转移过程，预测K → K的显着发射增强理论计算和实验观察都证实了高温下的直接转变。一方面，随着温度的升高，光载流子的估计种群比例的变化很好地支持了所提出的模型。另一方面，随温度变化的光致发光光谱清楚地表明，随着温度升高至760 K ，K → K的直接发射强度显着提高了约300倍。时间分辨荧光光谱研究证实了多层WS ₂中的波谷载流子转移过程。这些结果为提出的谷间载体转移模型提供了有力的证据。这种机制不仅可以用于提高间接带隙半导体的发光强度，而且可以进一步扩展到设计对控制载流子动态行为有特殊要求的光电器件。