We report plasmon resonant excitation of hot electrons in a photodetector based on a metal/oxide/metal (Au/Al₂O₃/graphene) heterostructure. In this device, hot electrons, excited optically in the gold layer, jump over the oxide barrier and are injected into the graphene layer, producing a photocurrent. To amplify this process, the bottom gold electrode is patterned into a plasmon resonant grating structure with a pitch of 500 nm. The photocurrent produced in this device is measured using 633-nm-wavelength light as a function of incident angle. We observe the maximum photocurrent at ±10° from normal incidence under irra-diation with light polarized parallel to the incident plane (p-polarization) and perpendicular to the lines on the grating, and a constant (angle-independent) photocurrent under irradiation with light polarized perpendicular to the incident plane (s-polarization) and parallel to the grating. These data show an amplification factor of 4.6× under resonant conditions. At the same angle (±10°), we also observe sharp dips in the photoreflectance corresponding to waveve-ctor matching between the incident light and the plasmon mode in the grating. In addition, finite-difference time-domain simulations predict sharp dips in the photoreflectance at ±10°, and the electric field intensity profiles show clear excitation of a plasmon resonant mode when illuminated with p-polarized light at this angle.

中文翻译：

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热电子驱动光电二极管的等离子体共振放大

我们报道了基于金属/氧化物/金属（Au / Al ₂ O ₃/石墨烯）异质结构。在该器件中，在金层中被光学激发的热电子跃过氧化物阻挡层，然后注入到石墨烯层中，从而产生光电流。为了放大此过程，将底部金电极图案化为间距为500 nm的等离激元谐振光栅结构。使用633 nm波长的光作为入射角的函数来测量此设备中产生的光电流。我们观察到，在垂直照射下，与入射平面平行（p偏振）且垂直于光栅上的线偏振的光，在垂直入射下与法向入射的最大光电流为±10°，并且在照射下具有恒定（与角度无关）的光电流。垂直于入射平面偏振（s偏振）并平行于光栅的光。这些数据显示放大倍数为4。在共振条件下为6倍。在相同的角度（±10°）下，我们还观察到光反射率出现急剧下降，这与入射光和光栅中的等离激元模式之间的波峰匹配有关。此外，有限差分时域仿真预测在±10°时光反射率会急剧下降，并且当以该角度用p偏振光照射时，电场强度曲线显示出清晰的等离子体激元共振模式激发。