Subcategory: Materials Science
Lauren Runkle - Pennsylvania State University
Co-Author(s): Fu Zhang, Chad Erb, and Nasim Alem, Pennsylvania State University, PA
Chemical vapor deposition (CVD) and mechanical exfoliation of synthesized layered van der Waals heterostructures composed of materials such as graphene and hexagonal boron nitride, as well as semiconducting transition metal dichalcogenides, provides the opportunity to generate scalable electronic and optoelectronic systems. Van der Waals-bonded two-dimensional layers of transition metal dichalcogenide (TMD) materials have a series of appealing properties when thinned down to the monolayer that differ from the semi-metallic character of graphene: direct band gaps, strong photoemission, and distinct electronic structures stemming from their spin-orbit coupling. These unique and practical properties prevalent in TMDs are enhanced when vertically stacked with the insulator hexagonal boron nitride, the best proven substrate to examine underlying characteristics of monolayer materials, as well as being stacked with graphene. In this study, the transition metal dichalcogenides were grown atop either mechanically exfoliated hexagonal boron nitride substrates or CVD graphene substrates via a chemical vapor deposition process. This CVD process was chosen for this study as opposed to manufacturing the heterostructures from transfer methods because it enabled more control over the orientation of the layers. This technique also helped bypass sample handling, which increased efficiency by eliminating a series of potential contaminations. This direct growth method utilized TEM grids as the substrate for heterostructure growth. Raman spectroscopy, transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM) were used in this study to examine the electronic, chemical, and atomic structures of the heterostructures, as well as their epitaxy. This van der Waals TMD heterostructure synthesization method could be appropriated to other van der Waals-bonded heterostructures, hinting that this process has potential for nanoelectronic applications.
Funder Acknowledgement(s): Funding for this project was provided by the National Science Foundation Emerging Frontiers in Research and Innovation 2D Materials Research and Mentoring (EFRI REM) program.
Faculty Advisor: Fu Zhang, firstname.lastname@example.org
Role: I was responsible for mechanical exfoliation of hexagonal boron nitride, as well as the synthesization of the transition metal dichalcogenides.