Quantum spin Hall materials hold the promise of revolutionary devices with dissipationless spin currents but have required cryogenic temperatures owing to small energy gaps. Here we show theoretically that a room-temperature regime with a large energy gap may be achievable within a paradigm that exploits the atomic spin-orbit coupling. The concept is based on a substrate-supported monolayer of a high-atomic number element and is experimentally realized as a bismuth honeycomb lattice on top of the insulating silicon carbide substrate SiC(0001). Using scanning tunneling spectroscopy, we detect a gap of ~0.8 electron volt and conductive edge states consistent with theory. Our combined theoretical and experimental results demonstrate a concept for a quantum spin Hall wide-gap scenario, where the chemical potential resides in the global system gap, ensuring robust edge conductance.

Two-dimensional (2D) atom lattices provide model setups with Coulomb correlations that induce competing ground states. Here, SiC emerges as a wide-gap substrate with reduced screening. We report the first artificial high-Z atom lattice on SiC(0001) by Sn adatoms, based on experimental realization and theoretical modeling. Density-functional theory of our triangular structure model closely reproduces the scanning tunneling microscopy. Photoemission data show a deeply gapped state (∼2  eV gap), and, based on our calculations including dynamic mean-field theory, we argue that this reflects a pronounced Mott-insulating scenario. We also find indications that the system is susceptible to antiferromagnetic superstructures. Such artificial lattices on SiC(0001) thus offer a novel platform for coexisting Coulomb correlations and spin-orbit coupling, with bearing for unusual magnetic phases and proposed topological quantum states of matter.

ABSTRACT(Si)GeSn is an emerging, group IV alloy system, offering new exciting properties, with great potential for low power electronics due to the fundamental direct bandgap and prospects as high mobility material. In this article we present a systematic study of HfO2/TaN high-k/metal gate stacks on (Si)GeSn ternary alloys and low temperature processes for large scale integration of Sn

Thin-film Mg/Si(111) Schottky diodes are exposed to oxygen to detect chemicurrents in the devices. The detected charge is created by nonadiabatic energy dissipation and due to either internal exoemission currents or surface chemiluminescence induced photocurrents. Both contributions can be distinguished by changing the metal film thickness of the device. Auger electron spectroscopy to study the oxygen uptake demonstrates that the chemicurrent transients represent truly the time dependent reaction rate at the surface. Model calculations indicate that the current monitors Mg oxide island nucleation and growth.

Preparation of SiC(0001) substrates is of high relevance to graphene growth. Yet, if only a smooth surface could be achieved, heteroepitaxy of many other two-dimensional materials comes into reach. Here we report a novel approach to hydrogen etching of SiC, based on stepwise ultrapure H exposure with slow substrate cooling rates. For the first time, the atomic evolution of the surface structure is witnessed by scanning tunneling microscopy. A detailed picture of the gas phase chemistry emerges, such as a zipper-like material desorption at step edges. The Si−C sheets are removed in layer-by-layer fashion, leading to large terraces with straight rims. The process ultimately results in an atomically smooth surface with complete H-passivation, with no detectable defect states in photoemission. The degree of perfection achieved suggests the use of this substrate as a versatile nanostructure template.