Presenter: Josiah Makinster
Faculty Mentor: Hailin Wang
Presentation Type: Poster 27
Primary Research Area: Science
Major: Physics
Funding Source: UROP Mini-Grant, University of Oregon, $1000
The electronic energy structures of exfoliated and chemical vapor deposition (CVD) grown single-layer Molybdenum Disulfide (MoS2) are investigated via photoluminescent spectroscopy to illuminate its potential in future semiconductor technology. Single-layer direct bandgap materials like MoS2 have applications in numerous areas, including light-emitting-diodes, flexible electronics, and solar cells, all of which will further advance through an understanding of its novel properties. Recently, it has been discovered that MoS2 is a material that can be cleaved into a microscopic sheet that is a single molecular layer thick, and shows novel physical properties that bulk MoS2 does not, including a strong photoluminescence (PL) that only emerges in the single-layer material due to a change in the electronic energy structure from an indirect bandgap to a direct bandgap. Here, PL spectra of exfoliated MoS2 and CVD-grown MoS2 are compared to assess the quality of the CVD-grown material, which tends to have a lower quality than exfoliated MoS2. Also, the PL spectrum of single-layer MoS2 is measured at cryogenic temperatures, because higher temperatures cause an increase in non-radiative recombination of excitons, which can potentially obscure important spectral features. We find that another PL peak emerges in the spectrum, indicating a high dependence of the electronic energy structure on temperature. All in all, theoretical results from literature that propose that single-layer MoS2 is a direct bandgap material are confirmed.