Research Highlights
Pennsylvania State University
Wafer scale epitaxial growth of unidirectional WS2 monolayers on sapphire
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. The domains must be oriented in the same crystallographic direction on the substrate to inhibit the formation of inversion domain boundaries (IDBs), which form when oppositely oriented triangular domains coalesce.
Pennsylvania State University
Stochastic Resonance In MoS2 Photodetector
In this project, we use a novel approach for next generation ultra-low-power sensor design by embracing the evolutionary success of animals with extraordinary sensory information processing capabilities that allow them to survive in extreme and resource constrained environments. Stochastic resonance (SR) is one of those astounding phenomena, where noise, which is considered detrimental for electronic circuits and communication systems, plays a constructive role in the detection of weak signals. Here, we show SR in a photodetector based on wafer-scale monolayer MoS2 for detecting ultra-low-intensity subthreshold optical signals from a distant light emitting diode (LED).
Pennsylvania State University
Phonons and excitons in ZrSe2 – ZrS2 alloys
ZrS2 has received increased attention due to its indirect band gap that matches with the visible spectrum and which is predicted to undergo an indirect-to-direct transition with strain. Alloying with ZrSe2 to produce ZrSxSe2-x (x=0...2) would provide continuous control over key optical and electronic parameters for photonics.
Pennsylvania State University
Can Ripples In Monolayer Sheets “Sweep Out” Unwanted Defects?
Atomically thin two-dimensional layers such as molybdenum disulfide, MoS2, are promising materials for nanoelectronics due to their exceptional electronic and optical properties. An inter-atomic potential has been developed that can accurately describe the thermodynamic and structural properties of MoS2 sheets, including defects and transitions between different structural phases.
Cornell University
When it Comes to Seeing Atoms, Blurrier is Better
One way to see atoms is to focus a beam of high-energy electrons to a tiny spot smaller than an atom and scan it around. The clarity of the resulting image is a tradeoff between collecting sufficient electrons to get a good signal, but too many electrons and the sample will be damaged.
Cornell University
Atomic-Scale Visualizations of Low-Temperature Phase Transitions
I. El Baggari, N. Sivadas, G.M. Stiehl, J. Waelder, D.C. Ralph, C.J. Fennie, L.F. Kourkoutis
Probing the structure of layered materials offers a gateway to better understand and potentially manipulate their electronic properties. While interactions within the individual layers are dominant, the proximity of neighboring layers significantly impacts the properties of such quasi-2D systems. Transition-metal dichalcogenides containing tellurium are especially noteworthy for their modulated structures and prominent interlayer contributions.
Pennsylvania State University
Deterministic Quantum Emission in an Epitaxial Two-Dimensional Material
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 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.
Pennsylvania State University
Two-Dimensional Grain Boundaries By Design
Grain boundaries are borders that separate crystals of distinct orientations and are generally considered as inevitable by-products of crystalline regions nucleating at different locations during growth. The MIP team has predicted how grain boundaries in two-dimensional crystals can form within a single grain by introducing bumps onto the substrate – the “floor” on which a 2D crystal grows.
Pennsylvania State University
Electronic changes in molybdenum dichalcogenides on gold surfaces
In this study, x-ray and ultraviolet photoelectron spectroscopy (XPS, UPS) were used to identify charge transfer processes and changes in the structural phase for MoS2, MoSe2 and MoTe2 monolayers on Au surfaces annealed up to 500oC.
Cornell University
Superconducting Sr2RuO4 films
H. P. Nair, J. P. Ruf, N.J. Schreiber, L. Miao, M. L. Grandon, D. J. Baek, B. H. Goodge, J. P. C. Ruff, L. F. Kourkoutis, K. M. Shen, D. G. Schlom
In virtually all implementations of a quantum computer, one of the states is an excited state that must, of necessity, decay spontaneously into its ground state. A fascinating alternative form of quantum computing has been proposed: braiding pairs of ground-state non-abelian anyons in two dimensions.
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