Optical and Optoelectrical Properties of Franckeite: A Naturally Occurring Van Der Waals Heterostructure
Abstract
In response to the mission of the Optoelectronics and Photonics Division of the Air force, we propose to investigate the intriguing optical and optoelectrical properties of the naturally occurring van der Waals heterostructure (vdWH) Franckeite (Fr). In Fr, we will probe functionalities at the atomically thin limit and potential use in novel nanoelectronics and nanophotonics applications. Van der Waals heterostructures (vdWHs) belong to the group of two-dimensional (2D) atomic crystals, in which layered van der Waals crystal (e.g., graphene, hexagonal boron-nitride, and transition metal dichalcogenides) are stacked in a predefined sequence to prepare designer heterostructures. Due to their intriguing properties, these atomically thin vdWHs are currently at the frontier of condensed matter physics and materials science research. They show great promise for the development of novel nanoscale electronic, optical and optoelectronic devices and for the fabrication of designer materials at the atomically thin limit. Currently, 2D vdWHs are fabricated synthetically in the laboratory by stacking 2D van der Waals crystals. This methodology relies on cumbersome placement methods of different atom layers, which is prone to unrepairable damages. These limitations are removed and new functionality is created, when nature is involved in creating the vdWH. This proposal will investigate the optical and optoelectronic properties of Fr that is comprised of alternating, weakly bonded, stacked pseudotetragonal lead sulfide (PbS) and pseudohexagonal tin sulfide (SnS2) layers. Unlike vdWHs prepared in the laboratory, the crystal orientation of the two neighboring layers in Fr are preserved across the sample and, simultaneously, the samples are free from fabrication related spurious interlayer adsorbates. The optical and optoelectronic properties of Fr originate from excitons, i.e., the bound state of an electron and a hole that form in a semiconductor when photons are absorbed. Two types of excitons in franckeite will be studied: interlayer excitons formed in the same layer and intralayer excitons formed in neighboring layers. The research will probe exciton formation and dissociation in Fr and the effect of dimensional confinement on exciton behavior. This goal will be accomplished by using microscopy and spectroscopy techniques: (i) optical microscopy; (ii) atomic force microscopy; (iii) scanning electron microscopy; (iv) energy-dispersive X-ray spectroscopy; (v) Raman spectroscopy; (iv) photoluminescence spectroscopy; and (vii) photocurrent spectroscopy. The proposed research will lay the foundation for exploiting excitons to prepare novel vdWHs with designer functionalities and vdWH-based optoelectronic devices for a wide range of scientific and consumer applications, including new wide band nanophotonic devices for surveillance and communication applications. The project will not only lay the groundwork for new advances in nanophotonics, but will also enhance STEM education at the Department of Physics & Astronomy at San Francisco State University (SFSU), a Hispanic Serving Institution, by engaging undergraduate and MasterÕs students in nanophotonic research focusing on students from underrepresented groups. It will engage the ethnically diverse students, mainly the physics and engineering majors, in stimulating research at the forefront of nanoelectronics and nanophotonic device physics- one of the areas of scientific interest to AFOSR and ARO. This training will increase the pool of STEM talent that is competent to fill the workforce needs of the DoD.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1910007
Entities
People
- Akm Newaz
Organizations
- Army Contracting Command
- Office of the Secretary of Defense
- San Francisco State University