Search

In this investigation, we have analyzed the structural, electrical, and optical behaviors of pure and composite thin films which are obtained from 2D monolayer molybdenum disulfide (MoS2) flakes, conjugated oligomer (CO) 1,4-Bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF), and by combining CO (BECV-DHF) with MoS2 in forms of CO/MoS2 composites. All the samples are coated on SiO2/Si substrates using the spin coating procedure where a spin-coating solution has been obtained by dispersing CO and MoS2 in ethanol or toluene. The structural morphology of MoS2 films and CO/MoS2 films of various thicknesses are analyzed using field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), and profilometer. These experimental results confirm the formation of MoS2 layer composite with oligomer nanocrystals. The optical properties of MoS2, CO, and CO/MoS2 films showed that the increased film thickness shifted the spectral peaks towards near infrared (NIR) and ultraviolet?visible (UV) regions of the electromagnetic spectrum. Moreover, devices such as solar cells, flexible memory cell and MOSFET were designed. The I-V characteristics of these devices show that CO/MoS2 composite films could serve as potential candidates for organic-inorganic nano-electronic device applications. ? 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Group IV alloys have attracted interest in the drive to create Si compatible, direct bandgap materials for implementation in complementary metal oxide semiconductor (CMOS) and beyond CMOS devices. The lack of a direct bandgap in Si and Ge hinders their incorporation into optoelectronic and photonic devices, without the induction of undesirable strain. Alloying of Ge with Sn represents a novel solution to the lack of light emission in group IV compounds, with an indirect-to-direct bandgap transition predicted for Ge at a Sn incorporation greater than 6.5 at. %. Recently, the initiatives on GeSn alloy research has turned its focus on nanoforms to keep track with the miniaturization of Si-related platforms for application in nano/optoelectronics, photonics and energy devices. Here, we review recent advances in the growth and application of Ge1-xSnx nanomaterials. An overview of theoretical band structure calculations for Ge1-xSnx and the effect of band-mixing is briefly explored to highlight the significance of Sn inclusion in Ge for band gap engineering. Different fabrication methods for growing Ge1-xSnx alloy nanostructures are delineated and corelated with thin films growth. This highlight the requirement of low-temperature, kinetically-driven non-equilibrium processess for growing these metastable nanoscale alloys. The optical and electrical properties for both Ge1-xSnx strain-relaxed one dimensional (1D) nanostructures and nanoparticles are reported with additional highlight on the recent key findings on Ge1-xSnx thin films to indicate the potential application of these materials in photonic, nanoelectronic and optotelectronic devices.

The utilization of charged domain walls (CDWs) as nanoelectronic devices requires three technological aspects to be developed: (1) controllable CDW creation, (2) tuning of CDW geometry, and (3) CDW removal. We have studied CDW formation in lithium niobate single crystals during polarization reversal using liquid and solid-state electrodes, as well as their combination. It was shown that CDW can be formed by two alternative procedures: (1) by forward switching for the liquid electrode at the Z+ polar surface and solid at the Z-one, (2) by backward switching for solid at the Z+ polar surface and liquid at the Z-one. The created CDW can be transformed to an almost neutral domain wall by the application of the field pulse of the reverse polarity for both procedures. As a result, the tilt of the formed CDW can be tuned reversibly in the range from 0.2° to 1.2° resulting in a change between isolated and highly conductive states. We have demonstrated that the created CDW can be used as a nanoelectronic channel for local electrolysis opening the additional possibilities for ferroelectric lithography. © 2019 Author(s).

A major bottleneck in the fabrication of efficient bio-organic nanoelectronic devices resides in the strong charge recombination that is present at the different interfaces forming the complex system. An efficient way to overcome this bottleneck is to add a self-assembled monolayer (SAM) of molecules between the biological material and the electrode that promotes an efficient direct electron transfer whilst minimising wasteful processes of charge recombination. In this work, the presence of a pyrene-nitrilotriacetic acid layer carrying different metal centers as SAM physisorbed on graphene is fully described by mean of electrochemical analysis, field emission scanning electron microscopy, photoelectrochemical characterisation and theoretical calculations. Our multidisciplinary study reveals that the metal center holds the key role for the efficient electron transfer at the interface. While Ni2+ is responsible for an electron transfer from SAM to graphene, Co2+ and Cu2+ force an opposite transfer, from graphene to SAM. Moreover, since Cu2+ inhibits the electron transfer due to a strong charge recombination, Co2+ seems the transition metal of choice for the efficient electron transfer., Comment: 28 pages, 7 figures

Long metallic nanowires combine crucial factors for nonconservative current-driven atomic motion. These systems have degenerate vibrational frequencies, clustered about a Kohn anomaly in the dispersion relation, that can couple under current to form nonequilibrium modes of motion growing exponentially in time. Such motion is made possible by nonconservative current-induced forces on atoms, and we refer to it generically as the waterwheel effect. Here the connection between the waterwheel effect and the stimulated directional emission of phonons propagating along the electron flow is discussed in an intuitive manner. Nonadiabatic molecular dynamics show that waterwheel modes self-regulate by reducing the current and by populating modes in nearby frequency, leading to a dynamical steady state in which nonconservative forces are counter-balanced by the electronic friction. The waterwheel effect can be described by an appropriate effective nonequilibrium dynamical response matrix. We show that the current-induced parts of this matrix in metallic systems are long-ranged, especially at low bias. This nonlocality is essential for the characterisation of nonconservative atomic dynamics under current beyond the nanoscale.

The fabrication of highly efficient bio-organic nanoelectronic devices is still a challenge due to the difficulty in interfacing the biomolecular component to the organic counterparts. One of the ways to overcome this bottleneck is to add a self-assembled monolayer (SAM) in between the electrode and the biological material. The addition of a pyrene–nitrilotriacetic acid layer to a graphene metal electrode enhances the charge transfer within the device. Our theoretical calculations and electrochemical results show that the formation of a pyrene–nitrilotriacetic acid SAM enforces a direct electron transfer from graphene to the SAM, while the addition of the Ni2+ cation and imidazole reverses the charge transfer direction, allowing an atomic control of the electron flow, which is essential for a true working device.

The achievable fidelity of many nanoelectronic devices based on superconducting aluminum is limited by either the density of residual nonequilibrium quasiparticles n_qp or the density of quasiparticle states in the gap, characterized by Dynes parameter \gamma. We infer upper bounds n_qp < 0.033 um^-3 and \gamma < 1.6*10^-7 from transport measurements performed on Al/AlOx/Cu single-electron transistors, improving previous results by an order of magnitude. Owing to efficient microwave shielding and quasiparticle relaxation, typical number of quasiparticles in the superconducting leads is zero., Comment: 5 pages, 3 figures; updated to revised version that was accepted for publication, contains data from a reference sample without qp traps

In this paper we perform a simulation study on the limits of graphene-nanoribbon field-effect transistors (GNR-FETs) for post-CMOS digital applications. Both conventional and tunneling FET architectures are considered. Simulations of conventional narrow GNR-FETs confirm the high potential of these devices, but highlight at the same time OFF-state leakage problems due to various tunneling mechanisms, which become more severe as the width is made larger and require a careful device optimization. Such OFF-state problems are partially solved by the tunneling FETs, which allow subthreshold slopes better than 60 mV/dec, at the price of a reduced ON-current. The importance of a very good control on edge roughness is highlighted by means of a direct simulation of devices with non-ideal edges.

We report quantitative electrical admittance measurements of diffusive superconductor--normal-metal--superconductor (SNS) junctions at gigahertz frequencies and millikelvin temperatures. The gold-palladium-based SNS junctions are arranged into a chain of superconducting quantum interference devices. The chain is coupled strongly to a multimode microwave resonator with a mode spacing of approximately 0.6 GHz. By measuring the resonance frequencies and quality factors of the resonator modes, we extract the dissipative and reactive parts of the admittance of the chain. We compare the phase and temperature dependence of the admittance near 1 GHz to theory based on the time-dependent Usadel equations. This comparison allows us to identify important discrepancies between theory and experiment that are not resolved by including inelastic scattering or elastic spin-flip scattering in the theory., Comment: 8 pages, 6 figures

cited By 0; Conference of SPIE Symposium on Gallium Nitride Materials and Devices VIII ; Conference Date: 4 February 2013 Through 7 February 2013; Conference Code:97274; International audience; Self-assembled GaN nanowires (NWs) currently are a subject of sustained interest in the scientific community motivated by both their potential applications for new LEDs, which should take benefit of the improved crystalline quality of those nano-objects, due to a strongly reduced defects density. In addition, interest of the scientific community for these 1D nano-systems is also related to the new fundamental questions opened by their strongly anisotropic geometry, and to their potential as possible building blocks for future nano-electronic devices. In this context, Raman spectroscopy has been increasingly used to study nitride NWs and several new phenomena have been reported to date with respect to these one-dimensional structures. In this work, both GaN and AlGaN nanowires grown by plasma-assisted Molecular Beam Epitaxy (MBE) have been experimentally investigated by scanning electron microscopy, atomic force microscopy and micro-Raman spectroscopy. Experimental results are analyzed and compared to theoretical ones obtained by dielectric models and Discrete Dipole Approximation (DDA) method. Evidence is given for original surface effects in the optical phonon physics related to both structural anisotropy of the material and 1D geometry of the GaN NWs. By using UV resonant excitation for AlGaN NWs in the whole range of composition, we demonstrate the selective excitation of AlGaN with the Al composition matching the energy of the exciting photons. Finally, we analyzed Raman data from single GaN NW after deposition on a flat substrate and we discuss the nature of strongly polarized A1(TO) phonon as a function of the NWs aspect ratio.