2DCC In-House Research Highlight

The recent study of intrinsic antiferromagnetic topological insulator Mn(Bi,Sb)₂Te₄ has attracted a great deal of interest, since it provides access to a variety of topological quantum states such as quantum anomalous Hall insulator and axion insulator. In this work, we report systematic c-axis transport studies under high magnetic fields (up to 35T) on Mn(Bi_1-xSb_x)₂Te₄.

Epitaxial graphene (EG) plays a crucial role in the confinement and stabilization of 2D group III metals and their nitrides at the EG/SiC interface, but the mechanism of intercalation and compound formation is not well understood. Here we demonstrate the role of EG functionalization and defect engineering of EG on the synthesis of 2D Ga and GaN_x using a combination of experiments and theory. Thinner regions of graphene are chemically functionalized with O forming C=O, C-O-C and C-OH bonds, whereas thicker regions of graphene are not chemically modified during plasma treatment.

Epitaxial growth of 2D transition metal dichalcogenides (TMDs) on sapphire has emerged as a promising route to wafer-scale single crystal films for large area device applications. Mirror twins, domains with opposite 0° and 60° orientation, are commonly observed in TMD epitaxy on high symmetry substrates such as c-plane sapphire. However, steps on the sapphire act as sites for TMD nucleation and can impart a preferred domain orientation resulting in a significant reduction in mirror twins.

Transition metal dichalcogenide (TMD)/graphene vertical heterostructures are attractive for optoelectronic and energy applications. However, microstructural heterogeneities in the graphene can impact the TMD nucleation and domain growth. A detailed investigation into the effects of the stacking order and twist angle of bilayer CVD graphene on the nucleation of WSe₂ was carried out.

2D InSe is known as a moderate bandgap semiconductor with direct to indirect bandgap crossover associated with a topological band alignment in the shape of an inverse Mexican hat when reduced to the monolayer thickness. Moreover, InSe has previously shown high electron mobility exceeding the values reported for black phosphorus or TMDs. Those properties elevate InSe to a highly interesting candidate for the realization of ultra-low power, high-performance FETs and highly efficient photodetectors.

Project Summary: An understanding of the surface chemistry of substrates used as support for 2D-chalcogenide growth is essential for controlling the synthesis of these materials. As such, we need computational methods that can be used to study the reaction dynamics of these support materials.

Project Summary: The performance of nanoscale metals in applications such as plasmonics, photodynamic therapy, and photocatalysis is influenced by their ability to absorb and transduce energy to their surroundings. In this study, we measured the non-equilibrium carrier dynamics in an air-stable 2-D polar metal heterostructures. Using transient absorption spectroscopy, the mechanism for energy dissipation was determined to involve contributions from the various components of the heterostructure, including the 2-D metal layer, SiC substrate, and graphene capping layer.

Project Summary: Metaheuristic algorithms such as simulated annealing (SA) has been implemented for optimization in combinatorial problems, especially for discreet problems. SA employs a stochastic search, where high-energy transitions (“hill-climbing”) are allowed with a temperature-dependent probability to escape local optima.

Project Summary: Realization of wafer-scale single-crystal films of transition metal dichalcogenides (TMDs) such as WS2 requires epitaxial growth and coalescence of oriented domains to form a continuous monolayer.

What Has Been Achieved: we carried out a careful study of the effect of 3 different capping layers on interfacial superconductivity in FeSe/SrTiO3 heterostructures.