Defect-mediated second order resonances in exfoliated black phosphorus

Orateur : Richard MARTEL (Université de Montréal)

Elemental nanomaterials, such carbon nanotube, graphene and exfoliated black phosphorus (bP), have been studied over the years for their intriguing low-dimensional semiconducting properties. The studies have been largely motivated by the advancement of flexible electronics, but also because of intriguing chemical, electrical and opt ical effects due to quantum confinement. Here we will discuss the specific case of exfoliated bP materials. Because of stability issues with bP in ambient conditions, we took advantage of a procedure carried out in a glove box to acquire the optical properties of the materials in their pristine and degraded states. Mono-, bi- and multi-layered bP samples were studied and the experiments with different excitation wavelengths reveal the presence of new Raman modes ascribed to Davydov-induced conversion of an infrared mode and to a defect-mediated process giving second-order Raman scattering. Through the use of the information obtained from these modes, the present study explains the discrepancies of Raman peak intensities and frequencies found in the literature on bP samples and opens alternative ways to explore the properties of exfoliated P(black), such as defects, doping levels, chemical reactivity and mechanical stress.

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