二维InSe薄片脊的增强发光
Enhanced Light Emission from the Ridge of Two-dimensional InSe Flakes
摘要：
InSe是一种新发现的二维（2D）半导体，具有优异的电学和光学性质，作为直接带隙半导体，具有从体到原子薄层的高迁移率，与其中直接带隙仅存在于单层极限的过渡金属二硫属化物（TMDC）截然不同。然而，InSe中的吸收主要由面外偶极子贡献主导，这导致垂直入射光的有限吸收，其只能在共振时激发面内偶极子。为了应对这一挑战，我们探索了一种独特的几何脊状态的二维薄片，而不影响样品的质量。我们观察到增强的吸收脊在很宽的范围内的激发频率从光电流和光致发光（PL）测量。此外，我们已经发现了新的PL峰在低温下，由于脊上的缺陷状态，这可以是高达~ 60倍强于本征PL峰的InSe。有趣的是，缺陷的PL是高度可调的，通过外部电场，这可以归因于斯塔克效应的局部缺陷。因此，InSe脊提供了操纵光-物质相互作用和缺陷工程的新途径，这对于基于2D半导体的新型光电子器件至关重要。
英文摘要：
InSe, a newly rediscovered two-dimensional (2D) semiconductor, possesses superior electrical and optical properties as a direct bandgap semiconductor with high mobility from bulk to atomically thin layers, drastically different from transition metal dichalcogenides (TMDCs) in which the direct bandgap only exists at the single layer limit. However, absorption in InSe is mostly dominated by an out-of-plane dipole contribution which results in the limited absorption of normally incident light which can only excite the in-plane dipole at resonance. To address this challenge, we have explored a unique geometric ridge state of the 2D flake without compromising the sample quality. We observed the enhanced absorption at the ridge over a broad range of excitation frequencies from photocurrent and photoluminescence (PL) measurements. In addition, we have discovered new PL peaks at low temperature due to defect states on the ridge, which can be as much as ~ 60 times stronger than the intrinsic PL peak of InSe. Interestingly, the PL of the defects is highly tunable through an external electrical field, which can be attributed to the Stark effect of the localized defects. InSe ridges thus provide new avenues for manipulating light-matter interaction and defect-engineering which are vitally crucial for novel optoelectronic devices based on 2D semiconductors.
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