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User Research Highlights

2DCC User Research Highlights 2019

The strongly spin-momentum coupled electronic states in topological insulators (TI) have been extensively pursued to realize efficient magnetic switching. However, previous studies show a large discrepancy of the charge-spin conversion efficiency. Moreover, current-induced magnetic switching with TI can only be observed at cryogenic temperatures. We report spin-orbit torque switching in a TI-ferrimagnet heterostructure with perpendicular magnetic anisotropy at room temperature. The obtained effective spin Hall angle of TI is substantially larger than the previously studied heavy metals. Our results demonstrate robust charge-spin conversion in TI and provide a direct avenue towards applicable TI-based spintronic devices.

LANL CINT scientists and their collaborators at UConn, AFRL, Penn State, and U. Oregon have discovered a method to create spatially localized quantum emission sites in a wafer-scale transition metal dichalcogenide film, WSe2, synthesized at the 2D Crystal Consortium (2DCC) facility. The team’s objective was to determine the role of strain in creating localized quantum emission sites in order to learn how to control their properties through strain.

Because the WSe2 was very thin, it conformed to the radius of ultra-sharp tips with sub-10 nanometer diameters, and bent towards the substrate. The resulting strain was enough to change the electronic structure, but only at the tips. The affected area emitted light that was fundamentally different in nature than that from the rest of the WSe2 film, where photons were ejected one-by-one, achieving what is referred to as deterministic quantum emission.

An undergraduate REU student at UConn participated in the research as is a co-author on the paper.

The team published the results as a Featured Article in the May 27th issue of Applied Physics Letters.

Link to LANL press release:

Monolayer 2D transition metal dichalcogenides (TMDs) have been a focus of increasing interest due to their unique properties but the development of device technologies has been hampered by difficulties in synthesizing large area monolayer and few layer films. We developed a multi-step process involving nucleation, ripening and preferential lateral growth to achieve epitaxial WSe2 monolayers on sapphire by gas source chemical vapor deposition. This process enables control of the nucleation density of WSe2 on the sapphire and the lateral growth rate of domains resulting in coalescence of monolayer regions over wafer-scale areas with minimal multilayer growth. The process also provides insights into the fundamental kinetic and thermodynamic factors that impact monolayer growth.