EFRI 2-DARE: 2D Crystals formed by Activated Atomic Layer Deposition

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Non-Technical: Transition metal chalcogenides (TMCs) crystallize as two-dimensional sheets of atoms, giving them unusual electronic properties that can be varied by changing the number, arrangement and compositions of the layers. The adjustment of these parameters provides manufacturing challenges that must be overcome to realize potential applications in electronics, photonics and related technologies. The project will research new deposition and processing methods for novel thin film and superconducting devices. This research will enable atomic level film formation at low temperatures that are compatible with low-cost glass and plastic substrates. Techniques to integrate metal contact layers and dielectric films with TMCs to produe working devices will also be researched. The project will support the research of five graduate students and summer research opportunities for undergraduates and high school students from underrepresented groups and economically challenged regions of Pennsylvania. Undergraduates will also participate in the project as part of their senior capstone engineering design project organized through the Learning Factory at Penn State.Technical: This EFRI 2-DARE project is aimed at the development of new synthetic routes and integration strategies for monolayer and multilayer transition metal chalcogenides (TMCs) to enable discovery of fundamental structure-property relationships, the exploration of novel physical phenomena, and the creation of new thin film and superconducting device technologies. An activated atomic layer deposition (ALD) process for WSe2, FeSe, NbSe2 and related 2D materials will be developed that incorporates thermal and plasma sources to promote precursor decomposition, thereby enabling reduced substrate temperatures that are needed for deposition and dielectric/metal integration on van der Waals surfaces. Epitaxial templating and substrate patterning will be used to control nucleation and promote in-plane forces to induce self-assembly of 2D islands over large areas. In-situ diagnostics will be used to provide insights into the ALD chemistry. Ultra-high resolution aberration-corrected (scanning) transmission electron microscopy ((S)TEM) imaging and related spectroscopy techniques will enable direct imaging and chemical characterization of defects in monolayer and multilayer films, providing information not always accessible by conventional TEM. Device fabrication processes will be developed to enable detailed studies of electrical transport and superconductivity in TMCs. Gated current-voltage measurements, Hall-effect, and quasi-static capacitance-voltage measurements will be used to characterize the transport properties of WSe2 and WS2 thin film devices. Superconductivity in gated FeSe and NbSe2 structures will also be examined to seek high-temperature and unconventional superconductivity.