In the present study, monochromated low-loss electron energy-loss spectroscopy in a scanning transmission electron microscope, confronted with ab-initio calculations, is used to investigate the bandgap and excitons energies of black phosphorus flakes in the near infrared region. Due to the monochromation of the electron beam and to a spectrometer with an energy resolution of 20 meV, a direct measurement of the narrow bandgap energy, E₀, of about 0.33 eV was successful, along with an intraband electronic transition E₁ at around 0.75 eV. Interestingly, additional transitions, excitonic in nature, are identified at 0.42 eV and 0.55 eV, the intensity of which increases with decreasing thickness. All these findings demonstrate the ability of monochromated low-loss electron energy loss spectroscopy to reveal unprecedented electronic and excitonic transitions in very narrow bandgap semiconductors.

在本研究中，使用透射电镜的单色低损耗电子能量损耗光谱法，从头开始计算，用于研究近红外区域中黑磷片的带隙和激子能量。由于电子束的单色化和能量分辨率为20 meV的光谱仪，成功地测量了约0.33 eV的窄带隙能量E ₀以及带内电子跃迁E ₁在0.75 eV左右。有趣的是，本质上为激子的其他跃迁被确定为0.42 eV和0.55 eV，其强度随着厚度的减小而增加。所有这些发现证明了单色低损耗电子能量损失谱仪能够揭示非常窄的带隙半导体中前所未有的电子和激子跃迁。