Institute of Physical and Theoretical Chemistry and LISA+, University of Tübingen , Auf der Morgenstelle 18, 72076 Tübingen, Germany.
ACS Nano. 2015 Aug 25;9(8):8176-83. doi: 10.1021/acsnano.5b02361. Epub 2015 Jul 29.
Here we demonstrate that photon emission induced by inelastic tunneling through a nanometer single gap between a sharp Au tip and an Au substrate can be significantly enhanced by the illumination of the junction with 634 nm laser light with an electric field component oriented parallel to the tip-axis, i.e., perpendicular to the sample. Analyzing photoluminescence (PL) spectra recorded as a function of bias voltage allows us to distinguish between PL from (1) the decay of electron-hole pairs created by the laser excited sp/d interband transition with a characteristic band at 690 nm and (2) the red-shifted radiative decay of characteristic plasmon modes formed by the gap. Since the electroluminescence spectra (without laser) already show the plasmonic gap modes, we conclude that the enhanced intensity induced by laser illumination originates from the radiative decay of hot electrons closely above the Fermi level via inelastic tunneling and photon emission into the plasmon modes. Since these processes can be independently controlled by laser illumination and the amplitude of the bias voltage, it is of great interest for designing new switchable photon emission plasmonic devices.
在这里，我们证明了通过在尖锐的 Au 尖端和 Au 衬底之间的纳米级单间隙进行非弹性隧穿，通过与尖端轴平行的电场分量（即垂直于样品）的 634nm 激光照射，可以显著增强光子发射。通过分析作为偏置电压函数记录的光致发光（PL）谱，可以区分（1）由激光激发的 sp/d 带间跃迁产生的电子-空穴对衰减引起的 PL，其特征带位于 690nm 处，以及（2）由间隙形成的特征等离子体模式的红移辐射衰减。由于电致发光光谱（无激光）已经显示出等离子体间隙模式，因此我们得出结论，激光照射引起的增强强度源自通过非弹性隧穿和光子发射到等离子体模式的费米能级以上的热电子的辐射衰减。由于这些过程可以通过激光照射和偏置电压的幅度独立控制，因此对于设计新型可切换光子发射等离子体器件非常有意义。
