Vapor phase morphology controlled growth of emerging 2d semiconducting materials for optoelectronics and energy harvesting

Thumbnail Image
Ghoshal, Debjit
Issue Date
Electronic thesis
Chemical engineering
Research Projects
Organizational Units
Journal Issue
Alternative Title
An increased thrust on smarter and more energy efficient devices has led to the search for newer materials with enhanced functionalities. While graphene has shown immense promise due to its layered structure and extremely high mobility in electronics and energy storage, it has limitations in that it is a zero bandgap material and hence is not an ideal candidate for energy harvesting devices or even optoelectronics. Emerging materials in the 2D materials family, which are semiconductors have shown promise in applications such as optoelectronics, flexible electronics and energy harvesting. However, in spite of their exceptional electronic and optoelectronic properties these materials are still far from commercialization. Major roadblock in the process is the limited understanding of the growth mechanism of these materials. This has resulted in growth of only specific morphologies of these materials and has resulted in limited application space. In this thesis, we demonstrate the applications of preferential morphology controlled growth of newer members of the 2D materials family for solar energy harvesting and optoelectronics. Our study points to some key morphologies (out of plane vertical growth, nanowire growth and thin films) and how these are critical to fabricate efficient devices with enhanced functionality. We demonstrate the application of Rhenium disulfide (ReS2), a 2D transition metal dichalcogenide that grows vertically on all substrates, as an effective photocatalytic agent for disinfecting water by deactivating bacteria in the presence of visible sunlight. We also demonstrate the application of this vertically grown ReS2 as a cold field emitter. The utility of such vertical ReS2 arrays in applications where high electric‐field enhancement are essential, such as surface enhanced Raman spectroscopy, is also demonstrated. We also demonstrate catalyst-free and morphology-controlled growth of 2D perovskite nanowires for polarized light detection. We show that the photoluminescence (PL) from the nanowires are highly polarized with a polarization ratio as large as ~ 0.73, which is one of the largest reported for perovskites. We also illustrate the use of these nanowires for the fabrication of polarization sensitive photodetectors. Finally, we demonstrate the importance of epitaxial thin film morphology of direct bandgap semiconductor PbI2 for applications in optoelectronics. We achieve large area epitaxial growth of PbI2 on Van Der Waals substrate mica. By a facile approach using electron back scattered diffraction (EBSD), we unambiguously understand the nature of grain boundaries in these epitaxial thin films. We also demonstrate the influence of growth rate of the film on the in plane crystal orientation as well as optical properties. The ability to reproducibly synthesize semiconductors with precise control over morphology and orientation could open up unique and hitherto unavailable opportunities for optoelectronics and beyond. Our findings shed light on some key mechanisms that dictate the morphology and orientation of growth during vapor deposition, thus enabling the ability to reproducibly grow specific morphologies enabling avenues for applications less explored.
August 2020
School of Engineering
Full Citation
Rensselaer Polytechnic Institute, Troy, NY
Terms of Use
PubMed ID