Tailoring electronic and photonic properties of van der Waals semiconductor heterostructures

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Nontechnical description: The ability to tailor materials at the nanoscale has been a key enabler for many technology breakthroughs, exemplified by the continuing development of semiconductors for computing and information technologies. Over the last few years, a new class of electronic materials has emerged - atomic crystals with a thicknesses of only one or a few atoms, known as two-dimensional materials. These materials systems provide a new platform for electronic and photonic devices. One interesting approach to investigating the nature of these materials is by stacking various types of them to form new hybrid layered materials. The electronic properties of the resulting stacks are governed by electrical forces and interactions between the various layers. This research explores the controlling factors that determine the interlayer interactions. Findings from this study are used to achieve rational design of stacks with desirable electronic and optical properties, which may be suitable for new types of optoelectronic devices. Educationally, a special topic course work is designed to introduce this new frontier of materials research to graduate and undergraduate students. In addition, a laboratory-based discovery process is designed to reach out to high school students through a summer internship program.Technical description: The introduction of semiconductor heterostructures enabled many novel designs of electronics and photonics, leading to transformative semiconductor technologies. The recent emergence of atomically thin crystalline two-dimensional (2D) semiconductors creates exciting new opportunities for pushing semiconductor heterostructures towards a new frontier. In particular, vertically stacked van der Waals (vdW) heterostructures were quickly recognized as a powerful platform for creating atomically thin heterostructures with great design flexibility. A central scientific issue is the role of interlayer coupling, which can alter the electronic structures of each vdW layer individually, and the stack as a whole. This project systematically investigates how interlayer atomic alignment impacts the electronic structure of vdW heterostructures. Moreover, using interlayer coupling as the design parameter, the research creates a sequence of 2D electronic superlattices with novel electronic and photonic properties. Scientifically, activities provide researchers in the field with important design parameters to tailor the electronic and photonic structures of vdW heterostructures. Technologically, the new generation of electronic and photonic materials and devices driven by this new line of research have important applications that benefit society. Educationally, graduate students trained through this study gain a broad scientific perspective. Through the design of a special course, the PI continues to enhance campus-wide graduate/undergraduate education in nanoscience and nanotechnology. The research also enables broadening participation of students from underrepresented groups.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.