Science Daily April 11, 2024 Studies of electric field-driven insulator-to-metal (IMT) in the prototypical vanadium dioxide (VO2) thin-film channel devices are largely focused on the electrical and elastic responses of the films, but the response of the corresponding Titanium dioxide (TiO2) substrate is often overlooked. An international team of researchers (USA – Pennsylvania State University, Cornell University, Argonne National Laboratory, Germany) found that in-operando spatiotemporal imaging of the coupled elastodynamics using X-ray diffraction microscopy of a VO2 film channel device on TiO2 substrate the film channel bulged during the IMT instead shrinking as expected. A micron thick proximal layer in […]
Tag Archives: semiconductors
Solving quantum mysteries: New insights into 2D semiconductor physics
Nanowerk October 16, 2023 An international team of researchers (Australia, Spain) has introduced a novel approach ‘quantum virial expansion,’ to uncover the complex quantum interactions in two-dimensional semiconductors. They showed that this constituted a perturbatively exact theory in the high-temperature or low-doping regime, where the electrons’ thermal wavelength was smaller than their interparticle spacing. They obtained exact analytic expressions for the photoluminescence and predicted new features such as a nontrivial shape of the attractive branch peak related to universal resonant exciton-electron scattering and an associated energy shift from the trion energy. The theory allowed them to formally unify the two […]
Scientists discover ‘flipping’ layers in heterostructures to cause changes in their properties
Nanowerk October 10, 2023 Assembling different TMD layers into vertical stacks creates a new artificial material called a van der Waals (vdW) heterostructure. By incorporating different materials, it becomes possible to combine the properties of individual layers, producing new optoelectronic devices with tailor-made properties. To understand the unusual stacking sequence, an international team of researchers (South Korea, Germany, USA – Oak Ridge National Laboratory) introduced the excitonic Elliot formula by imposing strain exclusively on the top layer that could be a consequence of the stacking process. They found that the intensity ratio of Q- to K-excitons in the same layer […]
Researchers improve the performance of semiconductors using novel 2D metal
Phys.org August 18, 2023 Metal contacts to MoS2 field-effect transistors play a determinant role in the device electrical characteristics and need to be chosen carefully. However, they suffer from high contact resistance because of the Schottky barrier and the Fermi level pinning effects that occur at the contact/MoS2 interface. To overcome this issue an international team of researchers (the Netherlands, India) investigated 2D metallic TiSx (x ∼ 1.8) as top contacts for MoS2 FETs using atomic layer deposition for the synthesis of both the MoS2 channels as well as the TiSx contacts and assessed the electrical performance of the fabricated […]
Potential application of unwanted electronic noise in semiconductors
Science Daily August 10, 2023 Random noise in magnetic materials is of potential use in systems such as spiking neuron devices, random number generators and probability bits. An international team of researchers (South Korea, China, USA – Harvard University, Montana State University) has shown electrically tunable magnetic fluctuations and random telegraph noise in multilayered vanadium-doped tungsten diselenide (WSe2) using vertical tunnelling heterostructure devices composed of graphene/vanadium-doped WSe2/graphene and magnetoresistance measurements. They identified bistable magnetic states through discrete Gaussian peaks in the random telegraph noise histogram and the 1/f2 features of the noise power spectrum. Three categories of fluctuation were detected: […]
A novel laser slicing technique for diamond semiconductors
Nanowerk August 1, 2023 Laser slicing is a technique of slicing materials along cracks formed by scanning a focused ultrashort-pulse laser beam inside the materials. Researchers in Japan proposed a novel slicing technique to fabricate diamond wafers and demonstrate slicing at the {100} surface. Cracks parallel to the {100} plane are needed to fabricate the wafer. However, crystal materials contain a cleavage plane at the {111} plane, which cracks easily. Typically, cracks propagate not only along the {100} plane, which was the intended slicing plane, but also along the {111} plane, which increased the kerf loss. To restrict these undesirable […]
Turning bacteria into solar factories with semiconductor nanoclusters
Nanowerk July 28, 2023 Semiconductor-based biointerfaces are typically established either on the surface of the plasma membrane or within the cytoplasm. In Gram-negative bacteria, the periplasmic space, characterized by its confinement and the presence of numerous enzymes and peptidoglycans, offers additional opportunities for biomineralization, allowing for nongenetic modulation interfaces. A team of researchers in the US (University of Chicago, Argonne National Laboratory, National Renewal Energy Laboratory) demonstrated semiconductor nanocluster precipitation containing single- and multiple-metal elements within the periplasm. The periplasmic semiconductors were metastable and displayed defect-dominant fluorescent properties. The defect-rich (i.e., the low-grade) semiconductor nanoclusters produced in situ could still […]
Researchers demonstrate novel way to convert heat to electricity
Nanowerk May 19, 2023 To compete with conventional energy-conversion technologies, a thermoelectric material must possess the mutually exclusive properties of both an electrical conductor and a thermal insulator. Recent theoretical investigations on sub-device scales have revealed that nanopillars attached to a membrane exhibit a multitude of local phonon resonances, spanning the full spectrum, that couple with the heat-carrying phonons in the membrane and cause a reduction in the in-plane thermal conductivity, with no expected change in the electrical properties because the nanopillars are outside the pathway of voltage generation and charge transport. A team of researchers in the US (NIST, […]
Organic semiconductors curl up in the dark
Nanowerk January 17, 2023 Organic semiconductors have the potential to replace their silicon predecessors in many applications. However, the manufacturing processes of solar cells that achieve such efficiencies are not yet compatible with mass production. An international team of researchers (Denmark, Germany) used roll-to-roll methos to print the organic semiconductor (poly(3-hexylthiophene) or P3HT), used for flexible solar cells, and organic electronics directly on a polymer film. In solution without illumination or under red light, the polymer chains quickly aggregated and formed ordered domains. When illuminated under green or blue light, the more rigid polymer chains, excited by the light, were […]
The best semiconductor of them all?
MIT News July 21, 2022 Among the ultrahigh–thermal conductivity materials, cubic boron arsenide (c-BAs) is predicted to exhibit simultaneously high electron and hole mobilities of >1000 centimeters squared per volt per second. Using the optical transient grating technique, a team of researchers in the US (MIT, University of Houston, UT Austin, Boston College) experimentally measured thermal conductivity of 1200 watts per meter per kelvin and ambipolar mobility of 1600 centimeters squared per volt per second at the same locations on c-BAs samples at room temperature despite spatial variations. Ab initio calculations show that lowering ionized and neutral impurity concentrations is […]