In Situ TEM and Ex Situ Studies of Two-Dimensional Nanostructured Devices

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Nontechnical Abstract:This NSF project focuses on an experimental investigation of novel two-dimensional nanostructured materials towards the fabrication and synthesis of one-dimensional electronic devices. This research combines fabrication of devices at the atomic scale in ultrathin materials with electrical characterization. The research team aims at advancing synthesis, characterization, and understanding of two-dimensional materials for an atom-by-atom control of structure-property-performance relationships while monitoring the evolution during device heating and electron irradiation and recording key device properties such as electron transport. More broadly, this project has impacts on education (university and K-12 students, on public forums: festivals and museum exhibits) and industry (e.g., on electron microscopy companies). The broader impact also includes the realization of low-dimensional materials and the advancement of devices including miniaturized electronics with improved power consumption. Moreover, this project impacts industries developing on-chip nanoscale devices. Outreach to a broad nanodevice community and to the electron microscopy industry includes open source software for analyzing data as well as the development of a novel equipment for advanced electron microscopy. The educational part provides innovative multidisciplinary learning opportunities for students at all levels, at the crossroads of electron microscopy and solid-state materials science in the Greater Philadelphia Area. To exploit the specific nature of this research project at the interface of physics and materials science, the PI's team participates in large public events in this metro area: the Nano Day at Penn, the Philadelphia Science Festival and the Philly Materials Day. The research team gives nanoscience presentations to high school students at the Penn Summer Science Academy and participates in the STEM outreach in the Philadelphia School District.Technical Abstract:This project exploits materials growth and materials irradiation by electron and ion beams to modify materials with nm-scale spatial and density control, towards engineering of their properties and observations of emerging phenomena that arise when material and device sizes are reduced and when single atomic layers of materials are stacked in a well-defined manner. This work establishes a more complete understanding of transport in low-dimensional materials that can enhance or replace silicon in future electronic-based devices. Thin atomic sheets are of particular interest since their electrical properties can be tuned by their geometry. Utilizing a novel experimental platform pioneered by the PI and state-of-the-art transmission electron microscopy instrumentation along with ex situ Raman spectroscopy, photoluminescence, and low temperature measurements, this project aims at understanding and controlling properties of thin materials such as nanosculpted structures for new multi-terminal electronic devices and few-nm-wide metal dichalcogenide nanoribbons. This research includes a comprehensive analysis toolkit enabling sub-angstrom device fabrication and atomically resolved property analysis. This work also advances device fabrication and characterization, thus opening the door to a wealth of unexplored physics. This research is organized into three primary cross-cutting themes: (1) growth, stacking, and electron microscopy characterization of two-dimensional layers and heterostructures, (2) electron beam nanosculpting and processing into one-dimensional nanodevices, and (3) nanodevice measurements. This project focuses on new materials including graphene, transition metal dichalcogenides (MoS2 and WS2) and topological thermoelectrics (Bi2Se3).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.