Vaquero Daniel, Salvador-Sánchez Juan, Clericò Vito, Diez Enrique, Quereda Jorge
Nanotechnology Group, USAL-Nanolab, Universidad de Salamanca, E-37008 Salamanca, Spain.
Nanomaterials (Basel). 2022 Jan 19;12(3):322. doi: 10.3390/nano12030322.
Two-dimensional transition metal dichalcogenides (2D-TMDs) are among the most promising materials for exploring and exploiting exciton transitions. Excitons in 2D-TMDs present remarkably long lifetimes, even at room temperature. The spectral response of exciton transitions in 2D-TMDs has been thoroughly characterized over the past decade by means of photoluminescence spectroscopy, transmittance spectroscopy, and related techniques; however, the spectral dependence of their electronic response is still not fully characterized. In this work, we investigate the electronic response of exciton transitions in monolayer MoSe via low-temperature photocurrent spectroscopy. We identify the spectral features associated with the main exciton and trion transitions, with spectral bandwidths down to 15 meV. We also investigate the effect of the Fermi level on the position and intensity of excitonic spectral features, observing a very strong modulation of the photocurrent, which even undergoes a change in sign when the Fermi level crosses the charge neutrality point. Our results demonstrate the unexploited potential of low-temperature photocurrent spectroscopy for studying excitons in low-dimensional materials, and provide new insight into excitonic transitions in 1L-MoSe.
二维过渡金属二硫属化物（2D-TMDs）是探索和利用激子跃迁最具前景的材料之一。二维过渡金属二硫属化物中的激子即使在室温下也具有显著长的寿命。在过去十年中，通过光致发光光谱、透射光谱及相关技术，二维过渡金属二硫属化物中激子跃迁的光谱响应已得到充分表征；然而，其电子响应的光谱依赖性仍未得到充分表征。在这项工作中，我们通过低温光电流光谱研究了单层MoSe中激子跃迁的电子响应。我们识别出与主要激子和三重激子跃迁相关的光谱特征，光谱带宽低至15毫电子伏特。我们还研究了费米能级对激子光谱特征位置和强度的影响，观察到光电流有非常强烈的调制，当费米能级穿过电荷中性点时，光电流甚至会发生符号变化。我们的结果证明了低温光电流光谱在研究低维材料中激子时尚未开发的潜力，并为单层MoSe中的激子跃迁提供了新的见解。
