Laboratory of semiconducting and photoactive "post-graphene" 2D materials, nanomaterials and nanocomposites

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Visible light, with wavelength between 400 nm and 700 nm, is at the core of optical sciences because it is simple to generate, reflect, transmit and detect it in so many different ways. Virtually any visible-light optical instrument available in everyday's life utilizes radiation that propagates at large distances over the size of the source that generates it. Unfortunately, this "far-field" optics is inherently limited by diffraction in the ability to resolve very small objects, with a resolving power no much less than a wavelength. This indicates that visible light in the far-field is unsuitable for the precise analysis of nanomaterials, quantum dots, and two-dimensional (2D) materials, in which spatial confinement below 1-100 nm is critical and has the potential of unique breakthroughs in terms of new physics and devices. Examples of new devices in which confinement effects are vital include: advanced solar cells that will make energy conversion cleaner, digital memory devices to make our big-data society simpler, nanoporous water filters to clean our environment, and heat spreaders to improve the lifetime of our portable electronics. We have acquired the skills to fabricate many of these devices in-house and, as a team of physicists, we are using proof-of-concept device prototypes to better understand the performance of specific materials incorporated into them. The most fundamental aspects of our research focus on the use of "near-field" visible radiation generated in the proximity of a nano-optical source to overcome diffraction, probe light-matter interaction at the nanoscale, and precisely infer the properties of specific 2D materials, nanomaterials and nanocomposites. We have unique expertise in aperture-type scanning near-field optical microscopy (SNOM) a near-field technique in which atomic force microscopy (AFM) cantilevers with sub-wavelength apertures drilled into them are used to generate localized near-field radiation and scan a sample in the close proximity of this source. Many optical techniques so far implemented only in the far-field will thus be extended to the near-field. The discovery of graphene, a 2D material entirely formed by carbon atoms, has spurred tremendous interest towards the potential of flat materials with confinement along the z-axis, but the next-generation of "post-graphene" 2D materials is still awaiting the most appropriate tools to be analyzed, manipulated and incorporated into proof-of-concept devices to understand their optical properties with high precision. Here, special emphasis will be placed on those 2D materials, nanomaterials and nanocomposites that, differently from graphene, exhibit semiconducting and photoactive properties, such as carbon quantum dots, aerogels, and 2D transition metal oxides and chalcogenides. SNOM tools capable of analyzing these systems are exciting and ideal to train the next-generation of diverse, inclusive and highly-qualified personnel in nano-optics and nano-physics.