Ultra-thin Black Phosphorus (BP) is a 2D semiconductor characterized by a direct and tunable band gap associated to high carriers mobility (1-3). Studying suspended thin layers of pristine BP is however challenging due to its strong degradation through a thickness dependent and photo-assisted oxidation reaction by adsorbed moisture oxygen (4). Using a protective transfer procedure from glovebox to our TEM-EELS operating at 40kV, we probe the dielectric response of suspended BP down to the monolayer in the range 0.5-40 eV, that include band gaps thresholds and surface/volume plasmons energies for BP. The dispersion of the plasmons as a function of the momentum is also measured and simulated for both in-plane crystallographic directions.

(1)Liu et al, ACS Nano (2014)
(2)Qiao et al, Nature Comm. (2014)

(3) Long et al, Nano Letter (2016)
(4)Favron et al, Nature Mater. (2015)