MIT News December 18, 2024 Although monolithic 3D (M3D) integration schemes show promise, the seamless connection of single-crystalline semiconductors without intervening wafers has yet to be demonstrated. An international team of researchers (USA – MIT, Korea) present a method for growing single-crystalline channel materials, specifically composed of transition metal dichalcogenides, on amorphous and polycrystalline surfaces at temperatures low enough to preserve the underlying electronic components. They demonstrated the seamless monolithic integration of vertical single-crystalline logic transistor arrays leading to the development of vertical CMOS arrays composed of grown single-crystalline channels. According to researchers their work provides opportunities for M3D integration […]
Tag Archives: semiconductors
Cooling with light: Exploring optical cooling in semiconductor quantum dots
Phys.org November 26, 2024 Highly efficient anti-Stokes (AS) photoluminescence (PL) is observed from halide perovskite quantum dots (QDs) due to their strong electron–phonon interactions. However, the PL quantum efficiency in QDs is primarily dominated by multiparticle nonradiative Auger recombination processes under intense photoexcitation, which impose limits on the optical cooling gain. Researchers in Japan investigated the Auger recombination of dot-in-crystal perovskites and quantitatively estimated the maximum optical cooling gain and the corresponding excitation intensity. Their optical cooling experiments demonstrated a maximum photo cooling of approximately 9 K from room temperature confirming that increasing the excitation intensity led to a transition […]
Optoelectronic diamond device reveals an unexpected phenomenon reminiscent of lightning in slow motion
Phys.org September 4, 2024 Establishing connections between material impurities and charge transport properties in emerging electronic and quantum materials requires new diagnostic methods tailored to these unique systems. Many such materials host optically-active defect centers which offer a powerful in situ characterization system, but one that typically relies on the weak spin-electric field coupling to measure electronic phenomena. An international team of researchers (Australia, USA – CUNY-The City College of New York) combined charge-state sensitive optical microscopy with photoelectric detection of an array of nitrogen-vacancy (NV) centers to directly image the flow of charge carriers inside a diamond optoelectronic device. […]
Research team discovers new property of light
Phys.org May 7, 2024 The nature of enhanced photoemission in disordered and amorphous solids is an intriguing question. An international team of researchers (Russia, USA – UC Irvine) studied structural photoemission in heterogeneous cross-linked silicon glass, a material that represents an intermediate state between the amorphous and crystalline phases, characterized by a narrow distribution of structure sizes. The model system showed a clear dependence of photoemission on size and disorder across a broad range of energies. While phonon-assisted indirect optical transitions are insufficient to describe observable emissions, their experiments suggested these could be understood through electronic Raman scattering. They attributed […]
‘Surprising’ hidden activity of semiconductor material spotted by researchers
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 […]
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 […]