论文标题
单层WS $ _2 $在扫描隧道显微镜中的电致发光：偏极性对发射光的光谱和角度分布的影响
Electroluminescence of monolayer WS$_2$ in a scanning tunneling microscope: the effect of bias polarity on the spectral and angular distribution of the emitted light
论文作者
论文摘要
扫描隧道显微镜（STM）中的非弹性电子隧道用于在单层钨二硫化物中生成激子（WS $ _2 $）。激发电致发光以正样品偏置和负样品偏置测量。使用光谱和傅立叶空间光学显微镜，我们表明隧道连接的极性决定了发光光的光谱和角度分布。在阳性样品偏见下，仅检测到具有平面过渡偶极矩的激素物种的发射。根据发射光的光谱分布，我们推断出主要的贡献是来自带电的激子，即Trions。在负样品偏见下，在发射光谱中证明了来自低能量激子物种的其他贡献，发射光的角度分布揭示了面内和面外过渡偶极矩的混合特征。
Inelastic electron tunneling in a scanning tunneling microscope (STM) is used to generate excitons in monolayer tungsten disulfide (WS$_2$). Excitonic electroluminescence is measured both at positive and negative sample bias. Using optical spectroscopy and Fourier-space optical microscopy, we show that the bias polarity of the tunnel junction determines the spectral and angular distribution of the emitted light. At positive sample bias, only emission from excitonic species featuring an in-plane transition dipole moment is detected. Based on the spectral distribution of the emitted light, we infer that the dominant contribution is from charged excitons, i.e., trions. At negative sample bias, additional contributions from lower-energy excitonic species are evidenced in the emission spectra and the angular distribution of the emitted light reveals a mixed character of in-plane and out-of-plane transition dipole moments.
