Quantification of defects engineered in single layer MoS2
Atomic defects are controllably introduced in suspended single layer molybdenum disulfide (1L MoS2) using helium ion beam. Vacancies exhibit one missing atom of molybdenum and a few atoms of sulfur. Quantification was done using a Scanning Transmission Electron Microscope (STEM) with an annular detector. Experimentally accessible inter-defect distance was employed to measure the degree of crystallinity in 1L MoS2. Correlation between the appearance of an acoustic phonon mode in the Raman spectra and the inter-defect distance was established, which introduces a new methodology for quantifying defects in 2D materials.
A roadmap for electronic grade 2D materials
2-dimensional materials hold promise for next-generation electronics. However, in order to realize 2D-based technologies, key milestones must be identified and met. This article identifies areas of research which are fundamentally required for achieving electronic grade 2D materials and brings together experts in these respective areas to discuss key challenges.
Spin-charge interconversion in a Dirac semimetal
This research explores room-temperature measurements of SCI at the interface between an archetypal Dirac semimetal (Cd3As2) and a conventional metallic ferromagnet (Ni0.8Fe0.2).
Closing the Loop on the 2D Materials Genome
The Two-Dimensional Crystal Consortium closely couples experimental synthesis and measurement with theoretical and computational work to close the discovery loop on the growth and characterization of 2D materials.
Benchmarking monolayer MoS2 and WS2 field-effect transistors
To assess the potential of transition metal dichalcogenides (TMDs) for future circuits, it is important to study the variation in key device parameters across a large number of devices. Here we benchmark device-to-device variation in field-effect transistors (FETs) based on wafer-scale monolayer MoS2 and WS2.
Growth of ultrathin Pt layers and selenization into PtSe2 by molecular beam epitaxy
Among the high-mobility two-dimensional transition metal dichalcogenides PtSe2 is of particular interest due to its record high carrier mobility of 1,000 cm2/Vs, sizeable band gap and air stability to address the current need for low-power, high-performance and ultra-thin body electronics.
Origami Without Fingers
Origami with regular paper can produce a limitless number of fascinating, beautiful and useful shapes, but we lack “fingers” at the nanoscale to guide the folding. Researchers in the Two-Dimensional Crystal Consortium at Penn State have conceived and simulated a novel way to “program” a folding pattern by patterning the nanoscale sheet with complementary regions of n-type and p-type doping.
Coupling Distinct Defect Species In 2D Crystals
Doping modulates the electronic, chemical, and mechanical properties of materials. For a two-dimensional tungsten disulfide, although an isolated molybdenum substitution only perturbs the host lattice negligibly, it couples strongly to common lattice defects such as sulfur vacancies, as verified by state-of-the-art electron microscopy and atomistic modeling techniques.
New Theory Tools for Modeling Growth of TMD Materials
The first ReaxFF force field developed for 2D-WSe2 provides the community with a highly efficient means that describe material growth, phase transitions, defect formation and migration and thus can provide valuable atomistic insights into experimental efforts on growth, phase, and defect engineering as a function of the local chemical environment. This potential can elucidate further the morphological evolution of monolayers in different environments in terms of loading conditions and defect concentrations/distributions. Interactions between vacancies and ripples in a 2D layers (“ripplocations”) suggest that vacancies could stabilize buckled structures by modulating the strain energy and possibly open a venue for sweeping out undesirable defects such as vacancies from 2D WSe2.
Tunneling Effects in Crossed Ta2Pt3Se8−Ta2Pd3Se8 Nanowire Junctions: Implications for Anisotropic Photodetectors
This study not only offers a way to build nanoscale junctions but also provides fundamental understandings of the electronic and optoelectronic properties of vdW nanowires and their heterojunctions.
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