Comprehensive Optical Band‐Edge Characterization for Multilayered MoTe 2 and Its Application in van der Waals‐Stacked Heterojunction Devices

作者：Yin‐Chou Huang, Dai‐Yan Yang, Luthviyah Choirotul Muhimmah, Yu‐Hung Peng, Ying Su, Ching‐Hwa Ho · 发表于：Small · 年份：2025 · DOI：10.1002/smll.202503542 · 被引用次数：7 · 研究领域：2D Materials and Applications、Perovskite Materials and Applications、MXene and MAX Phase Materials

Abstract MoTe 2 is considered a promising 2D material for solar energy and optoelectronic applications owing to its suitable bandgap value and specific excitonic behaviors. However, its band‐edge and excitonic transitions have not been fully elucidated. In this study, micro‐thermoreflectance (µTR) spectroscopy results show that multilayered 2H‐MoTe 2 exhibits multiple excitonic features, including A 1s , B 1s , A′, C, D, E, F, and G excitons, as well as one indirect‐gap related feature, observed in a 500 nm‐thick nanoflake at 300 K. Thickness‐dependent micro‐photoluminescence (µPL) measurement reveals that the PL emission is undetectable at a thickness of ≈40 nm (56 layers), but it is initially detected at 0.944 eV for a thinner thickness of ≈20 nm (28 layers), and finally, it shifts to 1.042 eV and presents the highest PL intensity when the thickness decreases to 5 nm (7 layers). Density functional theory (DFT) band structure calculations reveal that monolayer MoTe 2 is a direct semiconductor with the highest bandgap, which diminishes and finally converts to an indirect band with at ≈45 layers, nearly consistent with the thickness‐dependent µPL results. From the DFT calculations, the A 1s , B 1s , A′, C, D, E, F, and G band‐edge exciton features in the µTR spectra of multilayered MoTe 2 are verified and assigned. Additionally, a prototype p ‐SnS/ n ‐MoTe 2 stacking heterojunction device is fabricated. The built‐in potential of the heterojunction diode is ≈0.62 V, matching we...