Two-Dimensional Semiconductors for Quantum Science and Technologies

Semiconductors are the pillars of modern science and technologies. Their growing demand in high-performance systems for sensing, communications and computing, is paralleled by opportunities for future advances and innovative approaches to quantum information, Artificial Intelligence (AI) and fast, secure communication. These require an increasing miniaturization of materials, advanced methods to probe and manipulate their properties at the nanoscale, and the development of integration technologies for their use in functional devices for applications across different sectors.

Two-dimensional (2d) materials based on van der Waals (vdW) crystals provide an exciting platform for development of next generation 2d semiconductors (2SEM). Today, the family of vdW crystals comprises a “zoo” of over 1000 materials. However, only a few dozen of these have emerged as promising 2SEM. These materials can exist in a variety of stoichiometries, crystal structures and layer stacking sequences with physical properties of great interest for quantum science. The strong electron correlations, topological phases predicted in some of these systems do not have counterparts in traditional semiconductors. Although several concepts in solid-state physics still apply to these materials, standard theories have been revisited to describe these emerging quantum materials.

Here, I will review my research on 2SEM and present a unique-in-the world facility (EPI2SEM, https://bit.ly/3zN00dx) for EPItaxial growth and in situ analysis of 2SEM in ultra-high vacuum (UHV). EPI2SEM consists of a custom-designed reactor for molecular beam epitaxy (MBE) whose UHV operation matches the UHV requirements for in situ analytical techniques, such as RHEED (reflection high energy electron diffraction), SPM (scanning probe microscopy) and nanoESCA (electron spectroscopy for chemical analysis). By integration of growth, advanced microscopy and spectroscopy in UHV, we device methods to create atomically thin semiconductors with engineered physical properties beyond the current state-of-the-art. This approach will open new research directions and address many fundamental physics questions, advancing the science and applications of 2SEM.