As a fundamental surface property of two-dimensional (2D) materials, surface potential is critical for their emerging electronic applications and essential for van der Waals heterostructure engineering. Here, we report the surface potential of few-layer InSe. The effect of layer count, light intensity and different deposited substrates is considered. Few-layer InSe flakes were exfoliated from bulk InSe crystals on Si/SiO2 with 300-nm-thick thermal oxide and Si/SiO2 with 300-nm-thick thermal oxide and prefabricated micro-wells with 3 μm in diameter. The samples were measured by Kelvin probe force microscopy and tuned by an integrated 405-nm (3.06 eV) laser. Based on the work function of SiO2 (5.00 eV), the work functions of supported and suspended InSe are determined. These results show that the work function of InSe decreases with the increase in the layer count of both supported InSe and suspended InSe. Besides, by introducing a tunable laser light, the influence of light intensity on surface potential of supported InSe was studied. The surface potential (SP) and surface potential shift between light and dark states (∆SP =SPlight − SPdark) of supported InSe were measured and determined. These results present that the surface potential of supported InSe decreases with the increase in the light intensity and also decreases with the increase in the layer count. This is evident that light excites electrons, resulting in decreased surface potential, and the amount of electrons excited is correlated with light intensity. Meanwhile, ∆SP between light and dark states decreases with the increase in the layer count, which suggests that the influence of light illumination decreases with the increase in the layer count of few-layer InSe flakes.

中文翻译：

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二维硒化铟 (InSe) 薄片的层依赖和光可调表面电位

作为二维 (2D) 材料的基本表面特性，表面电位对其新兴的电子应用至关重要，对范德华异质结构工程至关重要。在这里，我们报告了几层 InSe 的表面电位。考虑了层数、光强度和不同沉积基材的影响。从具有 300 nm 厚热氧化物的 Si/SiO2 和具有 300 nm 厚热氧化物和直径 3 μm 的预制微孔的 Si/SiO2 上的块状 InSe 晶体剥离少层 InSe 薄片。通过开尔文探针力显微镜测量样品并通过集成的 405 nm (3.06 eV) 激光器进行调谐。基于 SiO2 (5.00 eV) 的功函数，确定了负载和悬浮 InSe 的功函数。这些结果表明，InSe 的功函数随着支持的 InSe 和悬浮的 InSe 层数的增加而降低。此外，通过引入可调激光，研究了光强度对负载型 InSe 表面电位的影响。测量并确定了支持的 InSe 的表面电位 (SP) 和表面电位在明暗状态之间的偏移 (ΔSP = SPlight - SPdark)。这些结果表明，负载 InSe 的表面电位随着光强度的增加而降低，并且随着层数的增加而降低。很明显，光激发电子，导致表面电势降低，激发的电子数量与光强相关。同时，明暗状态之间的ΔSP随着层数的增加而减小，