Oxygen impact on the electronic and vibrational properties of black phosphorus probed by synchrotron infrared nanospectroscopy

Author(s)

Grasseschi, D. ; Bahamon, D. A. ; Maia, F. C. B. ; Castro Neto, A. H. ; Freitas, R. O. ; de Matos, C. J. S.

• Document type: Journal article
• Source: 2D MATERIALS; v. 4, n. 3 SEP 2017.
• Web of Science Citations: 6

Abstract

Black phosphorus (BP) is a layered crystalline structure presenting a thickness-tunable direct bandgap and a high charge carrier mobility, with, therefore, enormous interest to photonics, optoelectronics and electronics. However, BP's high susceptibility to oxidation when exposed to ambient conditions is a critical challenge for its implementation into functional systems. Here, we investigate the degradation of BP flakes exposed to various environmental conditions by synchrotron infrared nanospectroscopy (SINS). As a near-field based technique, SINS provides sub-diffractional mid-infrared images and spectra from nano-sized domains. Supported by density functional theory (DFT) calculations, our SINS spectra reveal the formation of nanoscale POx domains, with x between 0.5 and 1, and a 100 meV red shift in the bandgap of flakes exposed to air for a few minutes. On the other hand, exposure to air for 24 h led to the preferential formation of H3PO4, with complete removal of the electronic transitions from the mid-infrared spectral window, while a long (1 month) exposure to low O-2 levels mainly led to the formation of P4O8 and P4O9 species. The SINS analysis allows correlating the morphology of oxidized samples to the oxide type, thus, contributing to a comprehensive characterization of the BP degradation process. (AU)

• FAPESP's process: 15/10405-3 - Synthesis, characterization, functionalization and ordering of metallic nanostructures
• Grantee: Daniel Grasseschi
• Support type: Scholarships in Brazil - Post-Doctorate
• FAPESP's process: 15/11779-4 - Plasmonic and nonlinear effects in graphene coupled to optical waveguides
• Grantee: Christiano José Santiago de Matos
• Support type: Research Projects - Thematic Grants
• FAPESP's process: 12/50259-8 - Graphene: photonics and opto-electronics: UPM-NUS collaboration
• Grantee: Antônio Hélio de Castro Neto
• Support type: Research Projects - SPEC Program