Magneto-transport properties in hybrid magnetic tunnel junctions (MTJs) integrating Self-Assembled Monolayers (SAMs) as tunnel barriers are critically influenced by spinterface effects, which arise from the electronic properties at ferromagnet (FM)/SAM interfaces. Understanding the mechanisms governing spinterface formation in well-controlled model systems is essential for the rational design of efficient molecular spintronic devices. However, the fabrication of FM/SAM/FM systems remains a significant challenge due to the difficulty in preventing electrical shorts through the SAM tunnel barrier during top FM electrode deposition. In this study, we address these challenges by developing model hybrid MTJs incorporating alkanethiol SAM tunnel barriers grafted under ultrahigh vacuum conditions onto single-crystalline Fe(001) bottom electrodes. A soft-landing deposition method is used for the deposition of a top Co FM electrode. The deposition process and the electronic properties of the formed FM/SAM interfaces are first studied by spatially integrated X-ray Photoelectron Spectroscopy (XPS). Furthermore, Ballistic Electron Emission Microscopy (BEEM) and spectroscopy are used to investigate the lateral homogeneity of the organic barrier. Optimal soft-landing deposition conditions allow the preparation of homogeneous Co/SAM interfaces with no evidence of metal diffusion through the SAM at the nanoscale. These observations are further confirmed at the micron scale by the high-yield patterning of large-area (5 & times; 5 mu m2) MTJs presenting fingerprints of electron tunneling through the SAM. These findings provide critical insights into the fabrication and optimization of molecular spintronic devices, paving the way for advancements in hybrid MTJ technology.

Photoelectron diffraction (PED) is a powerful spectroscopic technique that combines elemental resolution with a high sensitivity to the local atomic arrangement at crystal surfaces, thus providing unique fingerprints of selected atomic sites in matter. Stimulated by the rapid innovation in the development of various analysis methods for probing the atomic and electronic structures of van der Waals (vdW) heterostructures of two-dimensional materials, we present a theoretical assessment of the capacity of PED for extracting structural properties such as stacking, twist angles and interlayer distances. We provide a complete description of PED for the benchmark vdW heterostructure bilayer graphene (BLG), by calculating and analyzing the PED of BLG in Bernal and AA-stacking as well as twisted BLG for a wide range of the twist angle.

Integrating tunneling magnetoresistance (TMR) effect in memristors is a long-term aspiration because it allows to realize multifunctional devices, such as multi-state memory and tunable plasticity for synaptic function. However, the reported TMR in different multiferroic tunnel junctions is limited to 100%. This work demonstrates a giant TMR of -266% in La0.6Sr0.4MnO3(LSMO)/poly(vinylidene fluoride)(PVDF)/Co memristor with thin organic barrier. Different from the ferroelectricity-based memristors, this work discovers that the voltage-driven florine (F) motion in the junction generates a huge reversible resistivity change up to 106% with nanosecond (ns) timescale. Removing F from PVDF layer suppresses the dipole field in the tunneling barrier, thereby significantly enhances the TMR. Furthermore, the TMR can be tuned by different polarizing voltage due to the strong modification of spin-polarization at the LSMO/PVDF interface upon F doping. Combining of high TMR in the organic memristor paves the way to develop high-performance multifunctional devices for storage and neuromorphic applications.

We report on spin atomistic calculations used to model static and dynamic magnetic properties of inhomogeneous ultrathin iron films. Active magnetic layers in next-generation spintronic devices are becoming so thin that they exhibit some variable degree of roughness at the low scale making them magnetically inhomogeneous. We propose a multiscale approach to progressively shift from a rough atomic-scale system to an ensemble of macrospins. By studying nanoscale islands of atoms in contact with each other, we demonstrate that ultrathin rough layers can be described by a set of macrospins coupled by a Heisenberg-like exchange interaction driven by the existence and shape of nanoconstrictions linking the islands. We show that the magnetization dynamics at 0 K is strongly impacted by this surface morphology since the resonant frequency of a typical ultrathin iron layer can drop by up to an order of magnitude due to inhomogeneities. Additionally, we used Monte Carlo simulations to determine the ferromagnetic-paramagnetic and spin-reorientation transition temperatures for various morphology parameters and we show how nanoconstrictions and shapes of the atomic clusters can modify these transition temperatures. Our results demonstrate the possibility to account for the morphology of ultrathin structures with significant roughness. We believe that our approach makes it possible to model complete devices as close as possible to experimental reality.

We present the MsSpec Atomic Scattering Amplitude Package (MASAP), composed of a computation program and a graphical interface to generate atomic scattering amplitude (ASA) of an atom, either isolated or embedded in an environment, at any chosen energy of the impinging electron up to ≈15 KeV. The ASA is calculated using an effective, complex optical potential which provides damping effects in the scattering process in a fully relativistic framework. Optionally, scalar relativistic and non-relativistic approximations are also available to assess their applicability to a given problem. In order to describe electron propagation in solids we suggest to replace ASA's based on Plane Waves (PW) scattering with effective ASA's based on curved Spherical Waves (SW) using truncated-overlapped potentials of the Muffin-Tin (MT) type constructed according to the Mattheiss prescription. The graphical user interface generates not only ASA data files providing atomic Differential Cross Sections (DCS) but also files of related quantities such as total Cross Section (CS), both elastic and inelastic, atomic tl-matrices and phase shifts. We found in general that the imaginary part of the optical potential enhances the calculated elastic DCSs in the forward direction compared to the same potential without the imaginary part, a feature related to the optical theorem, but gives rise to a lower intensity at all other directions as expected due to the damping effect of the complex part of the potential. We show calculated differential and transport Cross Sections for aluminum and gold atoms both in isolation and in crystals with the Face-Centered-Cubic (FCC) structure.

Using angle-resolved photoemission spectroscopy, combined with first principle and coupled self-consistent Poisson-Schrödinger calculations, we demonstrate that potassium (K) atoms adsorbed on the low-temperature phase of 1T-TiSe_{2} induce the creation of a two-dimensional electron gas (2DEG) and quantum confinement of its charge-density wave (CDW) at the surface. By further changing the K coverage, we tune the carrier density within the 2DEG that allows us to nullify, at the surface, the electronic energy gain due to exciton condensation in the CDW phase while preserving a long-range structural order. Our Letter constitutes a prime example of a controlled exciton-related many-body quantum state in reduced dimensionality by alkali-metal dosing.

We present the first steps toward the development of MoS2/Si heterojunctions photovoltaics, essentially for integrated photonic devices applications. Therefore, we conjugate numerical device simulation, optical and structural characterizations, and density functional theory calculations. Through numerical device simulation, we show the potential of such solar cells, with attainable power conversion efficiencies of about 20%. Optical and structural characterizations of thin 2H-MoS2 layers deposited on SiO2 80nm/Si (001) substrates provides a path for the optimization of the 2D MoS2 material. With DFT calculations, we open the door for the optimization of the MoS2/Si interface, which is crucial for the device performances.

X-ray photoelectron diffraction is a powerful spectroscopic technique in the direct legacy of C.S. Fadley that combines high sensitivity to the arrangement of atoms in crystals and element specificity providing unique fingerprints of selected atomic sites in matter. When used with kinetic energies between 500 eV and 1500 eV, its interpretation and description is based on the fact that the atomic scattering factors are strongly forward-peaked in such a way that low-angles scattering and backscattering events are respectively dominant and almost irrelevant in the photoemission process. In this paper we aim to demonstrate with the help of multiple-scattering simulations that energy scans of high-energy (500-1500 eV) forward-scattering photoelectron diffraction can provide valuable structural and chemical information about thin epitaxial films or stacking of two-dimensional materials.

The luminescence of SrTiO3 depends on the sample type, either doped or stoichiometric, as grown or treated, the excitation conditions, and temperature. The origin of the luminescence emissions, blue, green, and infrared, remains controversial. In particular, the role played by defects, mainly oxygen vacancies, impurities, and selftrapped holes and electrons on the different emissions are far to be elucidated. We present a cathodoluminescence (CL) and photoluminescence (PL) study of undoped and Nb-doped samples. The different excitation conditions of CL and PL permit to distinguish the luminescence emission from the bulk (CL) and from a surface skin region (PL). Significant differences between both techniques are seen for the undoped sample, while the Nb-doped sample presents less differences, highlighting the role played by the surface defects and the doped electrons. The study is complemented by the temperature dependence of the luminescence spectra and the emission due to defects generated by plastic deformation.

A number of renormalization schemes for improving the convergence of multiple scattering series expansions are investigated. Numerical tests on a small Cu(111) cluster demonstrate their effectiveness, for example increasing the rate of convergence by up to a factor 2 or by transforming a divergent series into a convergent one. These techniques can greatly facilitate multiple scattering calculations, especially for spectroscopies such as photoelectron diffraction, Auger electron diffraction, low energy electron diffraction etc., where an electron propagates with a kinetic energy of hundreds of eV in a cluster of hundreds of atoms.

Silicon-based heterojunction (SHJ) solar cells demonstrate high efficiencies over their homojunction counterparts, revealing the potential of such technologies. We present here the first steps towards the development of molybdenum disulfide (MoS2)/c-silicon heterojunction solar cells, consisting of a preliminary study of the MoS2 material and numerical device simulations of MoS2/Si heterojunction solar cells, using SILVACO ATLAS. Through the optical and structural characterization of MoS2/SiO2/Si samples, we found a significant sensitivity of the MoS2 to ambient oxidation. Optical ellipsometry showed a bandgap of 1.87 eV for a 7 monolayer thick MoS2 sample, suitable for the targeted application. Finally, we briefly introduce a device simulation and show that the MoS2/Si heterojunction could lead to a gain in quantum efficiency, especially in the region with short wavelengths, compared with a standard a-Si/c-Si solar cell.

In this paper, we present the first steps of a process toward the development of MoS 2 /Si heterojunctions photovoltaics, using 2D 2H-MoS 2 , whose natural abundance and tunable bandgap make it suitable for such application. A focus is made here on the optimization of the MoS 2 material and its deposition process, through preliminary optical and structural characterizations of thin 2H-MoS 2 layers deposited on 80nm SiO 2 on top of Si (001) substrates. Our investigations revealed oxidation of the MoS 2 layers, and limited longitudinal crystallite size, which may strongly affect the band lineup between MoS 2 and Si, and thus, the performance of the solar cell.

Hybrid materials taking advantage of the different physical properties of materials are highly attractive for numerous applications in today's science and technology. Here, it is demonstrated that epitaxial bi‐domain III–V/Si are hybrid structures, composed of bulk photo‐active semiconductors with 2D topological semi‐metallic vertical inclusions, endowed with ambipolar properties. By combining structural, transport, and photoelectrochemical characterizations with first‐principle calculations, it is shown that the bi‐domain III–V/Si materials are able within the same layer to absorb light efficiently, separate laterally the photo‐generated carriers, transfer them to semimetal singularities, and ease extraction of both electrons and holes vertically, leading to efficient carrier collection. Besides, the original topological properties of the 2D semi‐metallic inclusions are also discussed. This comb‐like heterostructure not only merges the superior optical properties of semiconductors with good transport properties of metallic materials, but also combines the high efficiency and tunability afforded by III–V inorganic bulk materials with the flexible management of nano‐scale charge carriers usually offered by blends of organic materials. Physical properties of these novel hybrid heterostructures can be of great interest for energy harvesting, photonic, electronic or computing devices.

In this paper, we present the first steps of a process toward the development of MoS2/Si heterojunctions photovoltaics, using 2D 2H-MoS2, whose natural abundance and tunable bandgap make it suitable for such application. A focus is made here on the optimization of the MoS2 material and its deposition process, through preliminary optical and structural characterizat...