A5057595162- 2D Materials and Applications
- Graphene research and applications
- MXene and MAX Phase Materials
- Topological Materials and Phenomena
- Advanced Thermoelectric Materials and Devices
- Chalcogenide Semiconductor Thin Films
- Nanopore and Nanochannel Transport Studies
- Perovskite Materials and Applications
- Advanced Sensor and Energy Harvesting Materials
- Fuel Cells and Related Materials
- Random lasers and scattering media
- Extracellular vesicles in disease
- Conducting polymers and applications
- Molecular Junctions and Nanostructures
- Anodic Oxide Films and Nanostructures
- Thermal properties of materials
- Quantum and electron transport phenomena
- Membrane-based Ion Separation Techniques
- Advanced Semiconductor Detectors and Materials
- Spectroscopy Techniques in Biomedical and Chemical Research
- Advanced Electron Microscopy Techniques and Applications
- Semiconductor materials and interfaces
- Nanowire Synthesis and Applications
- Gold and Silver Nanoparticles Synthesis and Applications
- Ferroelectric and Negative Capacitance Devices
University of Pennsylvania
2015-2020
Pennsylvania State University
2017
Orthorhombic black phosphorus (BP) and other layered materials, such as gallium telluride (GaTe) tin selenide (SnSe), stand out among two-dimensional (2D) materials owing to their anisotropic in-plane structure. This anisotropy adds a new dimension the properties of 2D stimulates development angle-resolved photonics electronics. However, understanding effect has remained unsatisfactory date, shown by number inconsistencies in recent literature. We use absorption Raman spectroscopies...
We report how the presence of electron-beam-induced sulfur vacancies affects first-order Raman modes and correlate effects with evolution in situ transmission-electron microscopy two-terminal conductivity monolayer MoS2 under electron irradiation. observe a red-shift E' peak less pronounced blue-shift A'1 increasing dose. Using energy-dispersive X-ray spectroscopy selected-area diffraction, we show that irradiation causes partial removal dependence shifts S vacancy density (a few %). This...
Growth of transition metal dichalcogenide (TMD) monolayers is interest due to their unique electrical and optical properties. Films in the 2H 1T phases have been widely studied but some 1T′-TMDs are predicted be large-gap quantum spin Hall insulators, suitable for innovative transistor structures that can switched via a topological phase rather than conventional carrier depletion [Qian et al. Science 2014, 346, 1344−1347]. Here we detail reproducible method chemical vapor deposition...
Black phosphorus (BP) is a highly anisotropic allotrope of with great promise for fast functional electronics and optoelectronics. We demonstrate the controlled structural modification few-layer BP along arbitrary crystal directions sub-nanometer precision formation few-nanometer-wide armchair zigzag nanoribbons. Nanoribbons are fabricated, nanopores nanogaps, using combination mechanical–liquid exfoliation in situ transmission electron microscopy (TEM) scanning TEM nanosculpting. predict...
Two-dimensional materials are promising for a range of applications, as well testbeds probing the physics low-dimensional systems. Tungsten disulfide (WS2) monolayers exhibit direct band gap and strong photoluminescence (PL) in visible range, opening possibilities advanced optoelectronic applications. Here, we report realization two-dimensional nanometer-size pores suspended monolayer WS2 membranes, allowing electrical optical response ionic current measurements. A focused electron beam was...
Large-area growth of monolayer films the transition metal dichalcogenides is utmost importance in this rapidly advancing research area. The mechanical exfoliation method offers high quality material but it a problematic approach when applied to materials that are not air stable. One important example 1T'-WTe2, which multilayer form reported possess large non saturating magnetoresistance, pressure induced superconductivity, and weak antilocalization effect, electrical data for yet be due its...
Monolayer materials are sensitive to their environment because all of the atoms at surface. We investigate how exposure affects electrical properties CVD-grown monolayer MoS2 by monitoring parameters field-effect transistors as is changed from atmosphere high vacuum. The mobility increases and contact resistance decreases simultaneously either pressure reduced or sample annealed in see a previously unobserved, non-monotonic change threshold voltage with decreasing pressure. This result could...
Abstract The properties of van der Waals (vdW) materials often vary dramatically with the atomic stacking order between layers, but this can be difficult to control. Trilayer graphene (TLG) stacks in either a semimetallic ABA or semiconducting ABC configuration gate-tunable band gap, latter has only been produced by exfoliation. Here we present chemical vapor deposition approach TLG growth that yields greatly enhanced fraction and size domains. key insight is substrate curvature stabilize...
Heterostructures of transition metal dichalcogenides (TMDs) offer the attractive prospect combining distinct physical properties derived from different TMD structures. Here, we report direct chemical vapor deposition in-plane monolayer heterostructures based on 1H-MoS2 and 1T'-MoTe2. The large lattice mismatch between these materials led to intriguing phenomena at their interface. Atomic force microscopy indicated buckling in 1H region. Tip-enhanced Raman spectroscopy showed mode structure...
Nanopores are now being used not only as an ionic current sensor but also a means to localize molecules near alternative sensors with higher sensitivity and/or selectivity. One example is solid‐state nanopore embedded in graphene nanoribbon (GNR) transistor. Such device possesses the high conductivity needed for bandwidth measurements and, because of its single‐atomic‐layer thickness, can improve spatial resolution measurement. Here through shown during double‐stranded DNA (dsDNA)...
The combination of a nanopore with local field-effect transistor (FET-nanopore), like nanoribbon, nanotube, or nanowire, in order to sense single molecules translocating through the pore is promising for DNA sequencing at megahertz bandwidths. Previously, it was experimentally determined that detection mechanism due potential fluctuations arise when an analyte enters and constricts ion flow it, rather than theoretically proposed direct charge coupling between nanowire. However, there has...
We present a process for sculpting Bi2Se3 nanoflakes into application-relevant geometries using high-resolution transmission electron microscope. This takes several minutes to sculpt small areas and can be used cut the wires rings, thin of Bi2Se3, drill circular holes lines. determined that this method allows sub 10 nm features results in clean edges along drilled regions. Using situ imaging, selected area diffraction, atomic force microscopy, we found lithography preserves crystal structure...
A ferroelectric FET using MoS2 and PVDF-TrFE was fabricated, the effects of varying gate voltage scan rate from 200 mV/s to 4 investigated. Charge mobility, sub-threshold swing memory window width depended on rate. Prior switching on, a negative trans-conductance observed for all rates, followed by rapid increase in channel current state. model based nucleation domains unrestricted domain growth used explain these results. By lowering rate, performance polymer FE-FET’s can be improved.
Quantum valley Hall (QVH) domain wall states are a new class of one-dimensional (1D) one-way conductors that topologically protected in the absence mixing. Development beyond single QVH channel raises important questions as to how channels close spatial proximity interact with each other, and interaction may be controlled. Scalable epitaxial bilayer graphene synthesis produces layer stacking (LSW) bundles, where bound, providing an excellent platform study interactions. Here we show distinct...
We present a process for sculpting Bi$_2$Se$_3$ nanoflakes into application-relevant geometries using high resolution transmission electron microscope. This takes several minutes to sculpt small areas and can be used cut the wires rings, thin of Bi$_2$Se$_3$, drill circular holes lines. determined that this method allows sub 10-nm features results in clean edges along drilled regions. Using in-situ high-resolution imaging, selected area diffraction, atomic force microscopy, we found...