Journal
2D MATERIALS
Volume 8, Issue 2, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/2053-1583/abd89a
Keywords
black phosphorus; time-resolved ARPES; Stark effect; surface photovoltage; bandgap renormalization
Categories
Funding
- EU Graphene Flagship
- EPSRC [EP/K01711X/1, EP/K017144/1, EP/N010345/1, EP/L016087/1]
- ERC
- Italian PRIN project 2017BZPKSZ
- EPSRC [EP/K017144/1, EP/K01711X/1] Funding Source: UKRI
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Research shows that black phosphorous exhibits bandgap renormalization and valence band flattening after photoexcitation, with surface photovoltage counterbalancing Cs-induced surface band bending, helping to distinguish between bulk and surface electronic states.
Black phosphorous (BP) is a layered semiconductor with high carrier mobility, anisotropic optical response and wide bandgap tunability. In view of its application in optoelectronic devices, understanding transient photo-induced effects is crucial. Here, we investigate by time- and angle-resolved photoemission spectroscopy BP in its pristine state and in the presence of Stark splitting, chemically induced by Cs ad-sorption. We show that photo-injected carriers trigger bandgap renormalization, and a concurrent valence band flattening caused by Pauli blocking. In biased samples, photo-excitation leads to a long-lived (ns) surface photovoltage of few hundreds mV that counterbalances the Cs-induced surface band bending. This allows us to disentangle bulk from surface electronic states, and to clarify the mechanism underlying the band inversion observed in bulk samples.
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