Investigation and control of 2D-3D interfacial states

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Non-technical description: This project aims to experimentally investigate newly observed interfacial quantum states on heterojunctions of layered materials (e.g., graphene) and bulk semiconductors (e.g., silicone). These emerging states are independent of the intrinsic electronic structures of either the layered or bulk materials, but a novel interfacial effect, which enriches our current understanding of low-dimensional solid-state systems. This study opens alternative pathways towards artificial quantum structures for novel electronic, optoelectronic, and quantum technologies that are in line with the National Quantum Initiative Act. The scientific outcomes are disseminated via journals, conferences, and invited talks. More importantly, the research institute of this project, Georgia State University, is a historically minority-serving institution and top-ranked innovative teaching university. Many undergraduate and graduate students, especially underrepresented minority groups will be included in this cutting-edge research and prepare them for careers in science, technology, engineering, and mathematics. Undergraduate students typically continue their study in STEM graduate programs. Graduate students usually pursue their academic careers in universities, national laboratories, and federal research institutions or become leaders in the industries of semiconductors, information technology, etc. Furthermore, the project exposes the Greater Atlanta Area to the frontier of modern quantum science and technology via open houses, talks, summer internships so that the public and K-12 students get access to the state-of-the-art technology and latest scientific progress along with this research. Technical description: Fabrication of layered material heterostructures facilitates the construction of artificial quantum interactions, otherwise intangible in intrinsic materials. Currently, most of these emerging structures are interpreted by the well-established framework of in-plane electronic interactions, whereas a resonant tunneling behavior of graphene-silicon junctions recently discovered by the PI suggests the existence of out-of-plane quantum states, which is originated from an abrupt dimensional change on the interfaces. This new observation refreshes the understanding of reduced-dimensional materials and empowers new designs of artificial quantum structures, as such, necessitates a thorough investigation on the formation mechanism and control methods of these states without delay. For this purpose, this study primarily employs tunneling spectroscopy as the first experimental attempt to identify the determinative factors of these states, including transverse momentum mismatch, lattice orientations, and dielectric properties of the junctions. Following that, temperature-dependent measurements and in-situ atomic/molecular adsorption experiments also unveil the phonon-/defect-induced scattering and inelastic tunneling processes to explore the relaxation of these out-of-plane states. The investigation on these topics enables the construction of novel quantum devices, including layered multiple-well resonant tunneling transistors and resonant molecular detectors, to showcase the transformational potentials of this project. These efforts enrich our comprehension of the interfacial quantum interactions on reduced-dimensional heterostructures, meanwhile envision a breadth of new strategies for the design of terahertz light sources and detectors, cascade optoelectronics, and many other electronic, optoelectronic, and quantum architectures. Furthermore, the project is accompanied by extensive training and education for participating graduate, undergraduate students, and interns to accelerate their career trajectories in condensed matter physics and quantum science. It also promotes the public education of modern quantum science and technology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.