MgTe (110) semiconductor for a magnetic-element-free nonballistic spin-field-effect transistor
Not provided.
Materials Science↗
SEARCH · Engineering Papers
Results for “Semiconductor”
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Spin-lattice and spin-electronic interactions in the van der Waals semiconductor Co 2 P 2 S 6
Here, we report the results of a temperature-dependent reflection spectroscopy study, across a wide energy range (~ 0.01 to 3 eV), of unsubstituted and 40% Zn substituted for Co, for the transition-metal phosphorus trichalcogenide, Co 2 P 2 S 6 . We observe a transition from a paramagnetic to antiferromagnetic state with a Néel temperature at T N ~ 120 K that is completely suppressed in Zn-substituted samples. At 300 K we identify four narrow (~ 1 meV) infrared active phonon modes while at 70 K (below T N ) we observe that the low-energy phonons, dominated by Co motion, resolve into two modes. These low-energy modes are asymmetric, indicating coupling to a broad electronic continuum. We also report a broad (~ 30 meV) low-temperature infrared absorption band that appears near T N that we suggest is determined by a multiphonon-assisted 2-magnon absorption process. At 300 K in higher-energy spectra, we observe considerable absorption starting from 0.20 ± 0.02 eV which we associate with inter-Co 2+ ion 3d transitions. At temperatures below T N the number of electronic absorption bands increases from 4 to 6, indicating a lowering of the symmetry around the Co 2+ ions. On substituting 40% Zn for Co, the antiferromagnetic transition is suppressed along with temperature-dependent changes in the phonon and electronic spectra. The temperature-dependent spectral changes indicate strongly correlated behavior between the infrared active lattice vibrations, the electronic excitations, and magnetism in unsubstituted Co 2 P 2 S 6 .
2-dimensional systems↗
Effects of dynamical dielectric screening on the excitonic spectrum of monolayer semiconductors
Not provided.
Materials Science↗
Measuring the Migdal effect in semiconductors for dark matter detection
The Migdal effect has received much attention from the dark matter direct detection community, in particular due to its power in setting leading limits on sub-GeV particle dark matter. However, it is crucial to obtain experimental confirmation of the Migdal effect through nuclear scattering using Standard Model probes. In this work, we extend existing calculations of the Migdal effect to the case of neutron-nucleus scattering, with a particular focus on neutron scattering angle distributions in silicon. We identify kinematic regimes wherein the assumptions present in current calculations of the Migdal effect hold for neutron scattering and demonstrate that these include viable neutron calibration schemes. We then apply this framework to propose an experimental strategy to measure the Migdal effect in cryogenic silicon detectors using an upgrade to the NEXUS facility at Fermilab.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Localization Effect in Photoelectron Transport Induced by Alloy Disorder in Nitride Semiconductor Compounds
Near-band-gap photoemission spectroscopy experiments were performed on p-GaN and p-InGaN/GaN photocathodes activated to negative electron affinity. Here, the photoemission quantum yield of the InGaN samples with more than 5% of indium drops by more than 1 order of magnitude when the temperature is decreased while it remains constant for lower indium content. This drop is attributed to a freezing of photoelectron transport in p-InGaN due to electron localization in the fluctuating potential induced by the alloy disorder. This interpretation is supported by the disappearance at low temperature of the peak in the photoemission spectrum that corresponds to the contribution of the photoelectrons relaxed at the bottom of the InGaN conduction band.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Polaritonic Chern Insulators in Monolayer Semiconductors
Systems with strong light-matter interaction open up new avenues for studying topological phases of matter. Examples include exciton polaritons, mixed light-matter quasiparticles, where the topology of the polaritonic band structure arises from the collective coupling between matter wave and optical fields strongly confined in periodic dielectric structures. Distinct from light-matter interaction in a uniform environment, the spatially varying nature of the optical fields leads to a fundamental modification of the well-known optical selection rules, which were derived under the plane wave approximation. Here, in this study, we identify polaritonic Chern insulators by coupling valley excitons in transition metal dichalcogenides to photonic Bloch modes in a dielectric photonic crystal slab. We show that polaritonic Dirac points, which are markers for topological phase transition points, can be constructed from the collective coupling between valley excitons and photonic Dirac cones in the presence of both time-reversal and inversion symmetries. Lifting exciton valley degeneracy by breaking time-reversal symmetry leads to gapped polaritonic bands with nonzero Chern numbers. Through numerical simulations, we predict polaritonic chiral edge states residing inside the topological gaps. Our Letter paves the way for the further study of strong exciton-photon interaction in nanophotonic structures and for exploring polaritonic topological phases and their practical applications in polaritonic devices.
74 ATOMIC AND MOLECULAR PHYSICS↗
Continuous Mott Transition in Moiré Semiconductors: Role of Long-Wavelength Inhomogeneities
Recent experiments in moiré transition metal dichalcogenide materials have reported the observation of a continuous bandwidth-tuned transition from a metal to a paramagnetic Mott insulator at a fixed filling of one electron per moiré unit cell. The electrical transport measurements reveal a number of puzzling features that are seemingly at odds with the theoretical expectations of an interaction-induced, but disorder-free, bandwidth-tuned metal-insulator transition. In this Letter, we include the effects of long-wavelength inhomogeneities, building on the results for a continuous metal-insulator transition at fixed filling in the clean limit. We examine the effects of mesoscale inhomogeneities near the critical point on transport using the framework of random resistor networks, highlighting the salient differences from a simple percolation-based picture. Finally, we place our results in the context of recent and ongoing experiments.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Coexistence of Interacting Charge Density Waves in a Layered Semiconductor
Coexisting orders are key features of strongly correlated materials and underlie many intriguing phenomena from unconventional superconductivity to topological orders. Here, we report the coexistence of two interacting charge-density-wave (CDW) orders in EuTe 4 , a layered crystal that has drawn considerable attention owing to its anomalous thermal hysteresis and a semiconducting CDW state despite the absence of perfect FS nesting. By accessing unoccupied conduction bands with time- and angle-resolved photoemission measurements, we find that mono- and bi-layers of Te in the unit cell host different CDWs that are associated with distinct energy gaps. The two gaps display dichotomous evolutions following photoexcitation, where the larger bilayer CDW gap exhibits less renormalization and faster recovery. Surprisingly, the CDW in the Te monolayer displays an additional momentum-dependent gap renormalization that cannot be captured by density-functional theory calculations. This phenomenon is attributed to interlayer interactions between the two CDW orders, which account for the semiconducting nature of the equilibrium state. Finally, our findings not only offer microscopic insights into the correlated ground state of EuTe 4 but also provide a general non-equilibrium approach to understand coexisting, layer-dependent orders in a complex system.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Discovery of highly polarizable semiconductors BaZr S 3 and Ba 3 Zr 2 S 7
Not provided.
Materials Science↗
Tuning band alignment at a semiconductor-crystalline oxide heterojunction via electrostatic modulation of the interfacial dipole
In this paper, we demonstrate that the interfacial dipole associated with bonding across the SrTiO 3 /Si heterojunction can be tuned through space charge, thereby enabling the band alignment to be altered via doping. Oxygen impurities in Si act as donors that create space charge by transferring electrons across the interface into SrTiO 3 . The space charge induces an electric field that modifies the interfacial dipole, thereby tuning the band alignment from type II to III. The transferred charge, accompanying built-in electric fields, and change in band alignment are manifested in electrical transport and hard x-ray photoelectron spectroscopy measurements. Ab initio models reveal the interplay between polarization and band offsets. We find that band offsets can be tuned by modulating the density of space charge across the interface. Modulating the interface dipole to enable electrostatic altering of band alignment opens additional pathways to realize functional behavior in semiconducting hybrid heterojunctions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Mapping hidden space-charge distributions across crystalline metal oxide/group IV semiconductor interfaces
The electronic structures of semiconducting heterojunctions are critically dependent on composition including the presence and concentrations of dopants, both intended and unintended. Dopant profiles in the interfacial region can have major effects on band energies which in turn drive transport properties. Here, in this study, we use core-level photoelectron line shapes excited with hard x rays to extract information about electric fields resulting from internal charge transfer in epitaxial La 0.03 Sr 0.97 Zr x Ti 1–x O 3 /Ge(001) (0.1≤x≤0.7) heterostructures. Experiments were carried out for heterojunctions involving both n- and p-type Ge substrates. These heterojunctions were not amenable to electronic characterization of all regions by transport measurements because the doped substrates act as electrical shunts, precluding probing the more resistive films and masking interface conductivity. However, the core-level line shapes were found to be a rich source of information on built-in potentials that exist throughout the heterostructure, and yielded valuable insight into the impact of band bending on band alignment at the buried interfaces. The electronic effects expected for Ge with uniform n- and p-type doping are eclipsed by those of unintended oxygen dopants in the Ge near the interface. This study illustrates the power of hard x-ray photoemission spectroscopy and related modeling to determine electronic structure in material systems for which insight from traditional transport measurements is limited.
36 MATERIALS SCIENCE↗
Rashba effects in lead-free ferroelectric semiconductor [CH 3 PH 3 ]SnBr 3
Here, first-principles density functional theory computations are used to predict Rashba effects cofunctional with ferroelectricity in a recently synthesized lead-free hybrid organic-inorganic perovskite MPSnBr 3 (MP=methylphosphonium, [CH 3 PH 3 ] + ). The ground state of the material is polar monoclinic with calculated spontaneous polarization of 3.01 µC/cm 2 . It exhibits near band edges spin-splitting of up to 3.3 meV and Rashba coefficient up to 0.62 eV Å. The spin textures have different topology in the conduction and valence band, which originates from the difference in the spin-momentum coupling strengths. They occur in two orthogonal planes of the Brillouin zone and are coupled to the direction of spontaneous polarization. These features persist at a finite temperature of 293 K. At 333 K, that is above monoclinic to orthorhombic phase transition, spontaneous polarization is reduced to 0.15 µC/cm 2 , while the maximum spin splitting and Rashba coefficient reduce slightly to the value of 2.9 meV and 0.41 eV Å, respectively. The spin textures remain coupled with the polarization direction. We investigate the dependence of the aforementioned properties on the choice of computational methodology to extend the first-principles predictions to include finite temperature effects. We find that the predictions are sensitive to the methodology. Our study reveals the potential of MPSnBr 3 for low-temperature applications in spintronics and quantum computing.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Constraints on proximity-induced ferromagnetism in a Dirac semimetal ( Cd 3 As 2 ) / ferromagnetic semiconductor ( Ga 1 − x Mn x Sb ) heterostructure
Not Available
Mitra, Arpita (ORCID:0000000249590086)↗
First-principles predictions of Hall and drift mobilities in semiconductors
Not Available
Poncé, Samuel (ORCID:0000000311598389)↗
A Novel Scalable Array Design for III-V Compound Semiconductor-based Nonvolatile Memory (UltraRAM) with Separate Read-Write Paths
The dream of achieving a universal memory that can provide robust non-volatile memory states along with low-energy operation has been the key driving force of memory research. Despite dominating the memory market, conventional charge-based memories cannot satisfy these requirements. However, UltraRAM, an oxide-free charge-based memory cell, aims to achieve both of these requirements. This device achieves non-volatility (with an endurance of over 10 7 cycles and a retention of over 1000 years) along with switching at low-voltage (±2.3 V) utilizing a triple-barrier resonant tunneling (TBRT) structure made of InAs/AlSb. In this work, we propose an array design for UltraRAM-based memory devices. Our proposed memory array features separate read-write path and eliminates the possibility of accidentally switching the memory states stored in the array. Moreover, our design allows us to read all the cells in a column in one cycle without imposing any limit on the scalability. Besides, since the read operation in our proposed design is independent of the write mechanism, there is flexibility to optimize the read operation for memory and in-memory computing applications.
Alam, Shamiul↗
Study of Indium Chloride Vapor Treatment on Cu(In,Ga)Se 2 Semiconductor Thin Films
The recrystallization by indium chloride of Cu(In,Ga)Se 2 thin films deposited by co-evaporation at 350°C was studied. The process of recrystallization consists of the postdeposition treatment of CIGS sample by InCI3 vapor for 30 minutes with emphasis on grain growth. Here, the treatment resulted in uniform increased grain size and improved crystallinity. XRD measurements suggests the formation of indium rich phase. Dynamic SIMS were also performed to further understand the process, phase separation and the extent of gallium depletion.
14 SOLAR ENERGY↗
Studying the Recrystallization of Cu(InGa)Se 2 Semiconductor Thin Films by Silver Bromide In-situ Treatment
Cu(In,Ga)Se 2 samples were fabricated using a 3-stage thermal co-evaporation process on molybdenum back contact at low temperature. The process of recrystallization was carried out in between the 2 nd and 3 rd stages by flashing 25 mg of AgBr for 2 minutes. A change in morphological structure was observed as small grains transformed into large grains, as confirmed by XRD and SEM measurements. The decrease of the Ga gradient, seen in the SIMS depth profile, suggests Ga interdiffusion due to AgBr treatment. Altogether, the AgBr treatment contributes to a general improvement in device performance as compared to the as-deposited devices.
14 SOLAR ENERGY↗