Intercalation and High-Pressure Studies of Phosphorene: Pathways to Novel Materials and Physics


Tue, 30 Jul 2019, 10:00 am - 11:00 am
Natural Science Bldg. 312 - Louisville, KY
Current Doctoral Student Seminar
Manthila Rajapakse
University of Louisville
Candidacy Presentation


Phosphorene, a novel two-dimensional (2D) material, is gaining researchers’ attention due to its exceptional properties, including a unique layer structure, a widely tunable band gap, strong in- plane anisotropy, and high carrier mobility. Unlike graphene and most other 2D materials, phosphorene does not form atomically flat sheets, but has a puckered honeycomb structure due to its sp3 hybridization of atoms. The electronic bandgap of phosphorene varies from ≈0.3 eV for bulk material to ≈2 eV for a monolayer and such a strong dependence on the number of layers originate from the loss of interlayer hybridization in few layer systems. The highly tunable band gap along with other key characteristics such as high carrier mobility (≈300 cm2 V-1 s-1) and strong in-plane anisotropy, particularly the anisotropy of electric conductance, makes phosphorene a highly promising material for both nano and optoelectronic applications.

Short transport growth and liquid mechanical exfoliation methods are used to synthesize and exfoliate phosphorene respectively. Preliminary high-pressure studies carried out using Diamond Anvil Cell (DAC) and in-situ Raman spectroscopy shows that vibrational modes of pristine phosphorene are blue-shifted with increasing pressure. This blue-shift can be addressed in terms of charge redistribution between phosphorene layers and bond length/angle changes with the aid of Density Function Theory (DFT). Furthermore, the layered nature of the material makes phosphorene a good host for alkali metal intercalation such as Li and K. Preliminary work resulted in successful Li intercalation using electrochemical cells. Several material characterization techniques like Raman spectroscopy, Transmission Electron Microscopy (TEM) and optical microscopy was used to study the structural changes before and after intercalation. Proposed work including vapor-phase intercalation of potassium, conducting in-situ intercalation measurements with Raman spectroscopy, X-Ray Diffraction (XRD) and TEM using dedicated electrochemical cells and optimizing the DAC for high pressure studies of pristine, intercalated and de-intercalated phosphorene will be addressed. Extension of these techniques and studies to other novel 2D materials like Chromium Tri-iodide (CrI3) will also be discussed.


Natural Science Bldg. 312