Instrumentation for Surface Engineered van der Waals Nanoelectronic Heterostructures

Post-graphene two-dimensional (2D) materials have spurred not only fundamental research in materials physics but have also shown significant promise for a range of nanoelectronic applications. While transition metal dichalcogenides (TMDCs) posess a direct bandgap only at monolayer thickness, more recently invesitgated 2D materials such as phosphorene possess direct and tunable bandgaps at all thicknesses or promise high-Tc superconducitvity, making them highly desirable for next-generation nanolasers, photodetectors, and quantum devices. However, many of these emerging 2D materials are highly sensitive to perturbation during exposure to ambient conditions. Thus, harnessing the potential of these materials requires understanding their surface chemistry and developing robust passivation schemes. In particular, borophene is a monoelemental 2D material that was predicted to exist by ab initio calculations before successful synthesis in ultra-high vacuum (UHV). Metallic borophene has been predicted to be an impressive transparent conductor with and optical absorbance of 1% and show superconductivity with critical temperature of 10 – 20 K. However, progress in the physical characterizations of borophene, such as electrical or optical properties, is hampered by its reactivity in ambient conditions and difficulty in removal from its growth substrate. Through novel chemical functionalization, passivation schemes, and van der Waals heterojunctions, the Hersam laboratory has developed techniques for the manipulation and mitigation of the reactivity of various 2D materials. Herein, we propose to make prototype quantum devices that are uniquely enabled by ambient-reactive phosphorene and borophene. To achieve these goals, instrumentation to characterize these materials for electrical and optical properties is required including: (1) cryogen-free variable temperature (10 – 500 K) probe station with a 2.5 Tesla magnetic field; (2) supercontinuum white light tunable laser over a wavelength of 400 – 2300 nm; and (3) automated heterostructure assembly system in an inert atmosphere glove box. These tools constitute one comprehensive system that will allow automated transfer of different layered materials and simultaneous and in situ characterization of electrical, magnetic, and optical properties to enhance the impact of our existing ONR-funded projects.