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Toward Valleya??Coupled Spin Qubits
摘要： The bid for scalable physical qubits has attracted many possible candidate platforms. In particular, spin-based qubits in solid-state form factors are attractive as they could potentially benefit from processes similar to those used for conventional semiconductor processing. However, material control is a significant challenge for solid-state spin qubits as residual spins from substrate, dielectric, electrodes, or contaminants from processing contribute to spin decoherence. In the recent decade, valleytronics has seen a revival due to the discovery of valley-coupled spins in monolayer transition metal dichalcogenides. Such valley-coupled spins are protected by inversion asymmetry and time reversal symmetry and are promising candidates for robust qubits. In this report, the progress toward building such qubits is presented. Following an introduction to the key attractions in fabricating such qubits, an up-to-date brief is provided for the status of each key step, highlighting advancements made and/or outstanding work to be done. This report concludes with a perspective on future development highlighting major remaining milestones toward scalable spin-valley qubits.
关键词： valleytronics,qubits,quantum information,transition metal dichalcogenides,quantum dots
更新于2025-09-23 15:21:01
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Hybrid Single-Layer/Bulk Tungsten Diselenide Transistors by Lithographic Encoding of Material Thickness in Chemical Vapor Deposition
摘要： whose bulk-like (3D) portion can be used for metal contacts and efficient charge injection into the metal dichalcogenide (TMD) transistors; because of the small number of charge carriers in a 2D demonstrate that lithographic pre-patterning of a growth substrate prior to chemical vapor deposition of a TMD film can shape the TMD material into nanoscale hybrid 2D/3D structures enhanced reduction of performance compared to conventional bulk Schottky Barriers. Here we single-layer (2D) areas which serve as transistor channels with excellent mobilities and on-off Schottky-like barriers are an important limitation of the performance of single-layer transition semiconductor, the screening of metal contacts is inefficient leading to large depletion zones and devices (through 300nm of oxide) at realistic operation temperatures near 100°C using ratios. We observe mobilities of nearly 100 cm2V-1s-1 with an on/off ratio >105 for bottom-gated TMD growth. Bulk-like 3D WSe2 is observed to grow at the location of the hafnia, while 2D comparatively long channels (>5 microns) and absent other contact optimization. Our process involves lithographic patterning of a hafnium (IV) dioxide film onto the SiO2/Si substrate prior to allows us to extract Schottky barrier heights and other fundamental properties of our hybrid single-layer material is grown in regions of bare SiO2. Systematic evaluation of transport data devices.
关键词： Tungsten Diselenide,Schottky-Barrier,Transition Metal Dichalcogenides,2D Materials
更新于2025-09-23 15:21:01
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Two-dimensional transition metal dichalcogenides mediated long range surface plasmon resonance biosensors
摘要： Two-dimensional transition metal dichalcogenides (TMDCs), as promising alternative plasmon supporting materials to graphene, exhibit potential applications in sensing. Here, we propose a TMDCs-mediated long range surface plasmon resonance (LRSPR) imaging biosensor, which shows tremendous improvements in both imaging sensitivity (> ×2) and detection accuracy (> ×10) as compared to conventional surface plasmon resonance (cSPR) biosensor. It is found that the imaging sensitivity of the LRSPR biosensor can be enhanced by the integration of TMDC layers, which is di?erent from the previously reported graphene-mediated cSPR imaging sensor whose imaging sensitivity decreases with the number of graphene layers. This imaging sensitivity enhancement e?ect for the TMDCs-mediated LRSPR sensor originates from the propagating nature of the LRSPR at both interfaces of sensing medium/gold and gold/cytop layer (with matching refractive index as sensing medium). By tuning the thickness of gold ?lm and cytop layer, it is possible to achieve optimized imaging sensitivity for LRSPR sensor with any known integrated number of TMDC layers and the analyte refractive index. The proposed TMDCs-mediated LRSPR imaging sensor could provide potential applications in chemical sensing and biosensing applications.
关键词： detection accuracy,biosensor,long range surface plasmon resonance,Two-dimensional transition metal dichalcogenides,imaging sensitivity
更新于2025-09-23 15:21:01
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Self-hybridized exciton-polaritons in multilayers of transition metal dichalcogenides for efficient light absorption
摘要： Transition metal dichalcogenides (TMDCs) have attracted significant attention recently in the context of strong light-matter interaction. To observe strong coupling using these materials, excitons are typically hybridized with resonant photonic modes of stand-alone optical cavities, such as Fabry-Pérot microcavities or plasmonic nanoantennas. Here, we show that thick flakes of layered van der Waals TMDCs can themselves serve as low quality resonators due to their high background permittivity. Optical modes of such “cavities” can in turn hybridize with excitons in the same material. We perform an experimental and theoretical study of such self-hybridization in thick flakes of four common TMDC materials: WS2, WSe2, MoS2, and MoSe2. We observe splitting in reflection and transmission spectra in all four cases and provide angle-resolved dispersion measurements of exciton-polaritons as well as thickness-dependent data. Moreover, we observe significant enhancement and broadening of absorption in thick TMDC multilayers, which can be interpreted in terms of strong light-matter coupling. Remarkably, absorption reaches >50% efficiency across the entire visible spectrum, while simultaneously being weakly dependent on polarization and angle-of-incidence. Our results thus suggest formation of self-hybridized exciton-polaritons in thick TMDC flakes, which in turn may pave the way towards polaritonic and optoelectronic devices in these simple systems.
关键词： transition metal dichalcogenides,exciton-polaritons,strong coupling,nanocavities
更新于2025-09-23 15:21:01
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Atomistic mechanisms of seeding promoter-controlled growth of molybdenum disulphide
摘要： Seeding promoters facilitate the nucleation and growth of transition metal dichalcogenides in chemical vapor deposition (CVD). However, sophisticated roles of seeding promoter remain unclear. Here, adopting triangular-shaped crystal violet (CV) consisting of nonpolar and polar parts as the seeding promoter, we study the role of seeding promoter for the growth of molybdenum disulfide (MoS2). We systematically control the geometrical configuration of CV on SiO2/Si substrate by changing the solvent polarity and find that it strongly affects the growth of monolayer or multilayer MoS2 domains via CVD. Monolayer MoS2 domains were predominantly grown on randomly lying-down CV configurations on SiO2/Si substrate, whereas multilayer MoS2 domains are synthesized at concentrated polar parts in CV micelle on the substrate. Density functional theory calculations reveal that the initial nucleation step for the MoS2 growth is the adsorption of S on CV and the most favourable S adsorption site is the polar part in CV. Furthermore, it is found that the polar CV part mediates the CV adsorption to SiO2 and additionally strengthened in the lying-down CV configuration. Enhancing the thermal stability as well as hindering the re-aggregation of CV at high temperature, the lying down CV configuration allows the predominant growth of monolayer MoS2.
关键词： seeding promoter,molybdenum disulphide,chemical vapour deposition,transition metal dichalcogenides
更新于2025-09-23 15:19:57
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In situ atomic level studies of thermally controlled interlayer stacking shifts in 2D transition metal dichalcogenide bilayers
摘要： We show interlayer stacking shifts occur in transition metal dichalcogenides (TMD) bilayers due to the strain introduced during sample heating, and attributed to rippling of one layer relative to the other. The atomic structure of the interlayer stacking is studied using annular dark field scanning transmission electron microscopy with an in situ heating holder. Before heating, bilayers show uniform interlayer stacking of AA9 and AB. When heated, contrast change is seen and associated with interlayer stacking changes at the atomic scale due to ripples. When cooled down to room temperature, these contrast features disappear, confirming it is a reversible process that is not related to defects or vacancies. Because the bottom layer is attached to the in situ heating chip made from Si3N4 and the top layer is in contact with the underlying TMD layer with weak van der Waals interaction, the two layers experience different forces during thermal expansion.
关键词： transition metal dichalcogenides,thermal expansion,scanning transmission electron microscopy,interlayer stacking,2D materials
更新于2025-09-23 15:19:57
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Intrinsic-strain-induced curling of free-standing two-dimensional Janus MoSSe quantum dots
摘要： Motivated by the fascinating properties of both two-dimensional transition metal dichalcogenide quantum dots (TMD QDs) and Janus TMD monolayers, we theoretically explore the equilibrium structures of free-standing Janus MoSSe QDs in which atomic asymmetry of chalcogen is introduced. Two distinct types of spontaneous curling are observed by molecular dynamics simulations, and the curling behavior depends on the size of QD. The bowl-like (tube-like) curling occurs in relatively small (large) MoSSe QDs with di?erent shapes (hexagon and triangle) and edge types (zigzag and armchair). The transition between these two curling types occurs at the sizes of around 10 nm and 13 nm for hexagonal and triangular shapes, respectively. By applying equivalent mis?t strains into two adjacent sublayers, ?nite element analysis reproduces similar curling behavior. This con?rms the relaxation of intrinsic strain in Janus structure acting as the predominant driving force of spontaneous curling. In addition, the curvatures of Janus TMD QDs increase from MoSSe to MoSeTe to MoSTe, indicating the positive correlation between the curling and mis?t.
关键词： Intrinsic strain,Janus transition metal dichalcogenides,Molecular dynamics,Quantum dot,Finite element method
更新于2025-09-23 15:19:57
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Electrically controlled dielectric band gap engineering in a two-dimensional semiconductor
摘要： The emergent class of atomically thin two-dimensional (2D) materials has opened up completely new opportunities for manipulating electronic quantum states at the nanoscale. Here we explore the concept of dielectric band gap engineering, i.e., the controlled manipulation of the band gap of a semiconductor via its dielectric environment. Using first-principles calculations based on the GW self-energy approximation we show that the band gap of a two-dimensional (2D) semiconductor, such as the transition metal dichalcogenides, can be tuned over several hundreds of meV by varying the doping concentration in a nearby graphene sheet. Importantly, these significant band gap renormalizations are achieved via nonlocal Coulomb interactions and do not affect the structural or electronic integrity of the 2D semiconductor. We investigate various heterostructure designs, and show that, depending on the size of the intrinsic dielectric function of the 2D semiconductor, the band gap can be tuned by up to 1 eV for graphene carrier concentrations reachable by electrostatic doping. Our work provides opportunities for electrically controllable band gap engineering in 2D semiconductors.
关键词： GW self-energy approximation,transition metal dichalcogenides,graphene,two-dimensional semiconductor,dielectric band gap engineering
更新于2025-09-23 15:19:57
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Nanoscale Interfaces of Janus Monolayers of Transition Metal Dichalcogenides for 2D Photovoltaic and Piezoelectric Applications
摘要： Using first-principles calculations, we demonstrate a combination of two emergent fields, type-II van der Waal heterostructures and Janus structures, for the purpose of optimizing the harvesting of solar and nanoelectromechanical energy. The most stable stacking order in these nanoscale heterobilayers comprising of Janus monolayers of transition metal dichalcogenides has been ascertained based on the interlayer binding energies. The binding energies in WSeTe/WSTe and MoSeTe/WSTe heterobilayers are found to be -27.93 and -25.67 meV/?2 at an equilibrium interlayer layer distance of 3.25 ? and 3.32 ? respectively, indicating the exothermicity in the process of heterobilayer formation and hence, its experimental feasibility. The mechanical and dynamical stabilities have also been confirmed for these heterobilayers using the Born Huang stability criteria and phonon dispersion calculations. Our results unveil the mechanism underlying the electronic, piezoelectric, photocatalytic properties and carrier mobility in these Janus heterobilayers. Power conversion efficiency in the 2D ultrathin excitonic solar cells constituted by some of the heterobilayers studied in this work, has been found to lie in the range of 15-20%. Moreover, a very high carrier mobility (>200 cm2/V.s) together with a large visible light absorption coefficient (α ~ 105 cm-1) has been observed in these hetero-bilayers. The piezoelectric coefficients in these ultrathin heterobilayers (d33 = 13.91 pm/V) is found to reach close to the values obtained in multilayer/bulk structures built from Janus monolayers of Mo-based dichalcogenides. Our findings highlight the promising applications of these heterobilayers in ultrathin excitonic solar cells, nanoelectronics and nanopiezotronics.
关键词： van der Waals heterostructures,transition metal dichalcogenides,photovoltaic applications,Janus monolayers,piezoelectricity,carrier mobility
更新于2025-09-23 15:19:57
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Monolithic Contact Engineering to Boost Optoelectronic Performances of 2D Semiconductor Photovoltaic Heterojunctions
摘要： In optoelectronic devices based on two-dimensional (2D) semiconductor heterojunctions, the efficient charge transport of photogenerated carriers across the interface is a critical factor to determine the device performances. Here, we report an unexplored approach to boost the optoelectronic device performances of the WSe2-MoS2 p-n heterojunctions via the monolithic-oxidation-induced doping and resultant modulation of the interface band alignment. In the proposed device, the atomically thin WOx layer, which is directly formed by layer-by-layer oxidation of WSe2, is used as a charge transport layer for promoting hole extraction. The use of the ultrathin oxide layer significantly enhanced the photoresponsivity of the WSe2-MoS2 p-n junction devices, and the power conversion efficiency increased from 0.7 to 5.0%, maintaining the response time. The enhanced characteristics can be understood by the formation of the low Schottky barrier and favorable interface band alignment, as confirmed by band alignment analyses and first-principle calculations. Our work suggests a new route to achieve interface contact engineering in the heterostructures toward realizing high-performance 2D optoelectronics.
关键词： Contact engineering,Transition metal dichalcogenides,Heterostructures,Photovoltaics,2D semiconductors,Optoelectronics
更新于2025-09-23 15:19:57