Carl-von-Ossietzky University, Institute of Physics, D-26111 Oldenburg, Germany.
J Phys Chem Lett. 2023 May 4;14(17):3980-3985. doi: 10.1021/acs.jpclett.3c00642. Epub 2023 Apr 21.
Global photoluminescence (PL) and spatially resolved scanning tunneling microscopy (STM) luminescence are compared for thick CuO films grown on Au(111). While the PL data reveal two peaks at 750 and 850 nm, assigned to radiative electron decays via localized gap states induced by O vacancies, a wide-band emission between 700 and 950 nm is observed in STM luminescence. The latter is compatible with cavity plasmons stimulated by inelastic electron tunneling and contains no spectral signature of the CuO defects. The STM luminescence is nonetheless controlled by O vacancies that provide inelastic excitation channels for the cavity plasmons. In fact, the emission yield sharply peaks at 2.2 V sample bias, when tip electrons are resonantly injected into O defect states and recombine with holes at the valence-band top via plasmon stimulation. The spatially confined emission centers detected in photon maps of the CuO films are therefore assigned to excitation channels mediated by single or few O vacancies in the oxide matrix.
对在 Au(111) 上生长的厚 CuO 薄膜进行了全局光致发光 (PL) 和空间分辨扫描隧道显微镜 (STM) 发光的比较。PL 数据显示在 750nm 和 850nm 处有两个峰，归因于通过 O 空位诱导的局部能隙态的辐射电子衰减，而在 STM 发光中观察到在 700nm 到 950nm 之间的宽带发射。后者与由非弹性电子隧穿激发的腔等离子体相匹配，并且不包含 CuO 缺陷的光谱特征。然而，STM 发光受到 O 空位的控制，O 空位为腔等离子体提供了非弹性激发通道。事实上，当尖端电子通过等离子体激发共振注入到 O 缺陷态并与价带顶部的空穴复合时，发射产率在 2.2V 样品偏压下急剧峰值。因此，在 CuO 薄膜的光子图谱中检测到的空间受限发射中心被分配到由氧化物基质中单或少数 O 空位介导的激发通道。
