Intrinsic defects and mid-gap states in quasi-one-dimensional Indium Telluride

Recently, intriguing physical properties have been unraveled in anisotropic semiconductors, in which the in-plane electronic band structure anisotropy often originates from the low crystallographic symmetry. The atomic chain is the ultimate limit in material downscaling for electronics, a frontier for establishing an entirely new field of one-dimensional quantum materials. Electronic and structural properties of chain-like InTe are essential for better understanding of device applications such as thermoelectrics. Here, we use scanning tunneling microscopy/spectroscopy (STM/STS) measurements and density functional theory (DFT) calculations to directly image the in-plane structural anisotropy in tetragonal Indium Telluride (InTe). As results, we report the direct observation of one-dimensional In1+ chains in InTe. We demonstrate that InTe exhibits a band gap of about 0.40 +-0.02 eV located at the M point of the Brillouin zone. Additionally, line defects are observed in our sample, were attributed to In1+ chain vacancy along the c-axis, a general feature in many other TlSe-like compounds. Our STS and DFT results prove that the presence of In1+ induces localized gap state, located near the valence band maximum (VBM). This acceptor state is responsible for the high intrinsic p-type doping of InTe that we also confirm using angle-resolved photoemission spectroscopy.Comment: n

Reconfigurable Multifunctional van der Waals Ferroelectric Devices and Logic Circuits

In this work, we demonstrate the suitability of Reconfigurable Ferroelectric Field-Effect- Transistors (Re-FeFET) for designing non-volatile reconfigurable logic-in-memory circuits with multifunctional capabilities. Modulation of the energy landscape within a homojunction of a 2D tungsten diselenide (WSe$_2$) layer is achieved by independently controlling two split-gate electrodes made of a ferroelectric 2D copper indium thiophosphate (CuInP$_2$S$_6$) layer. Controlling the state encoded in the Program Gate enables switching between p, n and ambipolar FeFET operating modes. The transistors exhibit on-off ratios exceeding 10$^6$ and hysteresis windows of up to 10 V width. The homojunction can change from ohmic-like to diode behavior, with a large rectification ratio of 10$^4$. When programmed in the diode mode, the large built-in p-n junction electric field enables efficient separation of photogenerated carriers, making the device attractive for energy harvesting applications. The implementation of the Re-FeFET for reconfigurable logic functions shows how a circuit can be reconfigured to emulate either polymorphic ferroelectric NAND/AND logic-in-memory or electronic XNOR logic with long retention time exceeding 10$^4$ seconds. We also illustrate how a circuit design made of just two Re-FeFETs exhibits high logic expressivity with reconfigurability at runtime to implement several key non-volatile 2-input logic functions. Moreover, the Re-FeFET circuit demonstrates remarkable compactness, with an up to 80% reduction in transistor count compared to standard CMOS design. The 2D van de Waals Re-FeFET devices therefore exhibit groundbreaking potential for both More-than-Moore and beyond-Moore future of electronics, in particular for an energy-efficient implementation of in-memory computing and machine learning hardware, due to their multifunctionality and design compactness.Comment: 23 pages, 5 figures; Supporting Information: 12 pages, 6 figure

Quantum Confinement and Electronic Structure at the Surface of van der Waals Ferroelectric {\alpha}-In2_{2}Se3_{3}

Two-dimensional (2D) ferroelectric (FE) materials are promising compounds for next-generation nonvolatile memories, due to their low energy consumption and high endurance. Among them, {\alpha}-In$_{2}$Se$_{3}$ has drawn particular attention due to its in- and out-of-plane ferroelectricity, whose robustness has been demonstrated down to the monolayer limit. This is a relatively uncommon behavior since most bulk FE materials lose their ferroelectric character at the 2D limit due to depolarization field. Using angle resolved photoemission spectroscopy (ARPES), we unveil another unusual 2D phenomena appearing in 2H \alpha-In$_{2}$Se$_{3}$ single crystals, the occurrence of a highly metallic two-dimensional electron gas (2DEG) at the surface of vacuum-cleaved crystals. This 2DEG exhibits two confined states which correspond to an electron density of approximatively 10$^{13}$ electrons/cm$^{3}$, also confirmed by thermoelectric measurements. Combination of ARPES and density functional theory (DFT) calculations reveals a direct band gap of energy equal to 1.3 +/- 0.1 eV, with the bottom of the conduction band localized at the center of the Brillouin zone, just below the Fermi level. Such strong n-type doping further supports the quantum confinement of electrons and the formation of the 2DEG.Comment: 20 pages, 12 figure

A Novel Energy Optimization Approach for Electrical Vehicles in a Smart City

Electric Vehicles (EVs) have emerged rapidly across the globe as a powerful eco-friendly initiative that if integrated well with an urban environment could be iconic for the city’ host’s commitment to sustainable mobility and be a key ingredient of the smart city concept. This paper examines ways that will help us to develop a better understanding of how EVs can achieve energy use optimization and be connected with a smart city. As a whole, the present study is based on an original idea that would be useful in informing policy-makers, automotive manufacturers and transport operators of how to improve and embrace better EV technologies in the context of smart cities. The proposed approach is based on vehicles and buildings communication for sharing some special information related to the vehicle status and to the road condition. EVs can share their own information related to the energy experience on a specific path. This information can be gathered in a gigantic database and used for managing the power inside these vehicles. In this field, this paper exposes a new approach to power management inside an electric vehicle based on bi-communication between vehicles and buildings. The principle of this method is established on two sections; the first one is related to vehicles’ classification and the second one is attached to the buildings’ recommendation, according to the car position. The classification problem is resolved using the support vector classification method. The recommendation phase is resolved using the artificial intelligence principle and the neural network was employed, for giving the best decision. The optimal decision will be calculated inside the building, according to its position and using the old vehicle’s data, and transferred to the coming vehicle, for optimizing its energy consumption method in the corresponding building zone. Different possibilities and situations were discussed in this approach. The proposed power management methodology was tested and validated using Simulink/Matlab tool. Results related to the battery state of charge and to the consumed energy were compared at the end of this work, for showing the efficiency of this approach

Our experience in the podological analysis of children with motor disorders (20 cases)

Uvod: Pedijatrijski bolesnici s neuromotoričkim poremećajima često doživljavaju različita podijatrijska stanja. Učinkovitost i implikacije tretmana kao što su ortotika i ulošci u ovoj demografskoj skupini nisu u potpunosti shvaćene, naglašavajući značajnu prazninu u podijatrijskom istraživanju u kliničkoj praksi. Prikaz slučaja: Ova opservacijska studija analizirala je 20 pedijatrijskih bolesnika s neuromotoričkim poremećajima. Fokus je bio na uobičajenim stanjima stopala kao što su urasli nokti i hiperhidroza i njihovoj povezanosti s tretmanima poput ortotike, uložaka i kirurških intervencija poput produljenja Ahilove tetive. Klinička rasprava: Statistička analiza korištenjem hi-kvadrat testova otkrila je značajne povezanosti. Primjetno je da je korištenje ortotičkih pomagala povezano s većom učestalošću uraslih noktiju (χ² = 5,69, p = 0,017). Nasuprot tome, uporaba uložaka korelirala je s učestalom hiperhidrozom (χ² = 4,44, p = 0,035). Primijećena je I značajna tendencija za korištenjem ortoze kod pacijenata koji su bili podvrgnuti produljenju Ahilove tetive (χ² = 8,15, p = 0,017). Studija je također istaknula prevalenciju lomljivih noktiju i hiperkeratoze među sudionicima. Zaključak: Rezultati istudije naglašavaju ključnu ulogu podijatara u liječenju stanja stopala u pedijatrijskih bolesnika s neuromotornim poremećajima. Iako su intervencije poput ortoze općenito korisne, one također mogu pogoršati ili doprinijeti drugim stanjima, zahtijevajući redoviti i pažljivi podijatrijski nadzor. Studija zagovara buduća istraživanja s većim uzorkom i kontroliranim dizajnom studija kako bi se ta zapažanja dodatno potvrdila i proširila.Introduction and Importance: Pediatric patients with neuromotor disorders frequently experience various podiatric conditions. The effectiveness and implications of treatments like orthotics and insoles in this demographic are not thoroughly understood, highlighting a significant gap in podiatric research and clinical practice. Case Presentation: This observational study analyzed 20 pediatric patients with neuromotor disorders. The focus was on common foot conditions such as ingrown toenails and hyperhidrosis, and their association with treatments like orthotics, insoles, and surgical interventions like Achilles tendon lengthening. Clinical Discussion: Statistical analysis using chi-square tests revealed significant associations. Notably, orthotic use was linked to a higher incidence of ingrown toenails (χ² = 5.69, p = 0.017). In contrast, insole usage correlated with increased hyperhidrosis (χ² = 4.44, p = 0.035). Additionally, a significant tendency for orthotic use was observed in patients who underwent Achilles tendon lengthening (χ² = 8.15, p = 0.017). The study also highlighted the prevalence of brittle nails and hyperkeratosis among the participants. Conclusion: The findings emphasize the critical role of podiatrists in the management of foot conditions in pediatric neuromotor disorder patients. While interventions like orthotics are generally beneficial, they may also exacerbate or contribute to other conditions, necessitating regular and careful podiatric monitoring. The study advocates for future research with larger sample sizes and controlled study designs to further validate and expand upon these observation

Photoferroelectric All-van-der-Waals Heterostructure for Multimode Neuromorphic Ferroelectric Transistors

International audienceInterface-driven effects in ferroelectric van der Waals (vdW) heterostructures provide fresh opportunities in the search for alternative device architectures toward overcoming the von Neumann bottleneck. However, their implementation is still in its infancy, mostly by electrical control. It is of utmost interest to develop strategies for additional optical and multistate control in the quest for novel neuromorphic architectures. Here, we demonstrate the non-volatile electrical and optical control of the ferroelectric polarization states of Ferroelectric Field Effect Transistors (FeFET). The FeFETs, fully made of ReS 2 /hBN/CuInP 2 S 6 van der Waals materials, achieve an On/Off ratio exceeding 10 7 , a hysteresis memory window up to 7 V wide, and multiple remanent states with a lifetime exceeding 10 3 s. Moreover the ferroelectric polarization of the CuInP 2 S 6 (CIPS) layer can be controlled by photo-exciting the vdW heterostructure. We perform wavelength-dependent studies which allow for identifying two mechanisms at play in the optical control of the polarization: band-toband photocarrier generation into the 2D semiconductor ReS 2 , and photovoltaic voltage into the 2D ferroelectric CIPS. Finally, heterosynaptic plasticity is demonstrated by operating our FeFET in three different synaptic modes: electrically stimulated, optically stimulated, and optically assisted synapse. Key synaptic functionalities are emulated including electrical long-term plasticity, optoelectrical plasticity, optical potentiation, and spike rate-dependent plasticity. The simulated artificial neural networks demonstrate an excellent accuracy level of 91% close to ideal-model synapses. These results provide a fresh background for future research on photo-ferroelectric van der Waals systems, and put ferroelectric vdW heterostructures on the roadmap for next neuromorphic computing architectures

Direct Reconstruction of the Band Diagram of Rhombohedral-Stacked Bilayer WSe 2 –Graphene Heterostructure via Photoemission Electron Microscopy

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Van der Waals epitaxial growth of few layers WSe2 on GaP(111) B

We acknowledge the financial support from the Tunne2D (ANR-21-CE24-0030) and ADICT (ANR-22-PEEL-0011) projects, as well as from the French technological network RENATECH and Region Hauts-de-France.International audienceAbstract 2D material epitaxy offers the promise of new 2D/2D and 2D/3D heterostructures with their own specific electronic and optical properties. In this work, we demonstrate the epitaxial growth of few layers WSe 2 on GaP(111) B by molecular beam epitaxy. Using a combination of experimental techniques, we emphasize the role of the growth temperature and of a subsequent annealing of the grown layers under a selenium flux on the polytype formed and on its structural and morphological properties. We show that a low growth temperature promotes the formation of the 1T′ and 3R phases depending on the layer thickness whereas a higher growth temperature favours the stable 2H phase. The resulting layers exhibit clear epitaxial relationships with the GaP(111) B substrate with an optimum grain disorientation and mean size of 1.1° and around 30 nm respectively for the 2H phase. Bilayer 2H WSe 2 /GaP(111) B heterostructures exhibit a staggered type II band alignment and p-doped character of the epi-layer on both p and n-type GaP substrates. This first realisation of stable p-type WSe 2 epi-layer on a large-area GaP(111) B substrate paves the way to new 2D/3D heterostructures with great interests in nanoelectronic and optoelectronic applications, especially in the development of new 2D-material p-n junctions

Stacking order and electronic band structure in MBE-grown trilayer WSe2_2 films

International audienceFew-layer quantum materials, such as transition-metal dichalcogenides (TMDs), are paving the path to the design of high-efficiency devices in the field of microelectronics and optoelectronics. However, heterostructures of quantum materials coming from different families, while they would immensely broaden the range of possible applications, remain challenging. Here, we demonstrate the large-scale integration of compounds from two highly multifunctional families: the three-dimensional conventional semiconductor GaP and the two-dimensional TMD semiconductor WSe$_2$ which is particularly interesting in terms of its potential for electronic, spintronic, and photonics applications. We show that a 2H-2H (or AA′A) trilayer of WSe$_2$ can be grown by molecular-beam epitaxy (MBE) onto gallium phosphide (GaP) substrate. A sharp, high-quality WSe$_2$-GaP interface was confirmed by scanning high-resolution transmission electron microscopy and x-ray photoemission spectroscopy. We present a combined experimental and theoretical study of the structure of the valence band of trilayer WSe$_2$. Nanoangle-resolved photoemission spectroscopy and density-functional theory calculation show that trilayer electrons populate two distinct subbands associated with the K and Γ valleys, with effective masses along the ΓM direction about 0.27 and 0.5me, respectively (me is the bare electron mass)