The Jess & Mildred Fisher College of Science & Mathematics

School of Emerging Technologies

Exploring the Physics of Novel Two-Dimensional Systems

Dr. Jia-An Yan & Dr. Jeffrey R. Simpson (Physics, Astronomy and Geosciences)

Graphene, a hexagonally-arranged sheet of carbon only one atom thick, was first fabricated in 2004. Since then, this two-dimensional (2D) material has attracted tremendous interest from the condensed matter physics, materials science, chemistry, nanoscience, and nanotechnology research communities. Due to its remarkable electronic and mechanical properties, promising applications of graphene span from nanoelectronic, optoelectronic, and nanomechanical devices to ultrasensitive chemical sensor and bolometric detectors. Graphene has emerged as a transformative material for its great potential to dramatically change the current status of nanoscience and nanotechnology.

The great success of graphene also stimulated interest in related 2D systems. Our proposed research on novel 2D materials includes the monolayer silicon sheet (silicene) and monolayer molybdenum disulfide (MoS2). These 2D systems are at the cutting edge of the physics of advanced materials, and are globally recognized as an area with promises for the development of new nanoscale device technologies.

We are investigating the electronic and particularly the vibrational properties of silicene and single-layer MoS2, through a combined theoretical and experimental study, which includes computational modeling based on density functional theory (DFT) and experimental Raman spectroscopic measurements. Raman spectroscopy directly probes the vibrational (phonon) modes, while the DFT-based computational study provides a strong theoretical support in understanding, and even predicting, phenomena that can be verified by experiments. Our results will provide deep physical insight into these novel 2D systems, and hence facilitate their characterization, fabrication, and application in future technology.

Impact on Students

Two graduate students and two undergraduate students are currently involved in this project.

Related Work
  • Electron-Phonon Coupling in Silicene, Jia-An Yan and Mei-Yin Chou, Bulletin of the American Physical Society (BAPS) March Meeting 58, T5.014 (2013).
  • Electron-Phonon Coupling in Two-Dimensional Germanene, Ryan Stein**, David Schaefer, and Jia-An Yan, BAPS March Meeting 58, F5.012 (2013).
  • Surface Vibrational Modes in Multilayer Graphene, Gregoary Coard* and Jia-An Yan, BAPS March Meeting 58, V1.024 (2013).
  • Temperature-dependent photoluminescence and Raman spectroscopy of single-layer MoS2,Jeffrey R. Simpson, Rusen Yan, Simone Bertolazzi, Andras Kis, Jacopo Brivio, Michael Watson**, H. Grace Xing, and Angela R. Hight Walker, BAPS March Meeting 58, T5.007 (2013).
  • Development of Micro-Raman Spectroscopic Instrumentation for Measurement of Novel 2D Materials, Michael Watson**, Zach Thompson**, and Jeffrey R. Simpson, BAPS March Meeting 58, Q1.328 (2013).
  • Electric-field effects on the optical vibrations in AB-stacked bilayer graphene, Ryan Stein**, D. Hughes**, and Jia-An Yan, Phys. Rev. B 87, 100301(R) (2013).

*   TU Undergraduate Student
** TU Graduate Student

People
Towson students working on the project

Towson Undergraduate students Jeffery Demers (left, background) and Logan Scheel (right, foreground) perform micro-Raman spectroscopy on monolayer graphene sample.

MoS2 flake containing monolayer regions suspended over holes in thin Si3N4 substrates.

MoS2 flake containing monolayer regions suspended over holes in thin Si3N4 substrates.

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