Many Applications In Electronics Research Articles

Self-Diffusion of Ge in Amorphous Ge x Si1-x Films Studied In Situ by Neutron Reflectometry.

Ge x Si1-x alloys are gaining renewed interest for many applications in electronics and optics, especially for miniaturized devices showing quantum size effects. Point defects and atomic diffusion play a crucial role in miniaturized and metastable systems. In the present work, Ge self-diffusion in sputter deposited amorphous Ge x Si1-x alloys is studied in situ as a function of Ge content x = 0.13, 0.43, 0.8, and 1.0 by neutron reflectometry. The determined Ge self-diffusivities obey the Arrhenius law in the investigated temperature ranges. The higher the Ge content x, the higher the Ge self-diffusivity at the same temperature. The activation enthalpy decreases with x from 4.4 eV for self-diffusion in pure silicon films to about 2 eV self-diffusion in Ge0.8Si0.2 and Ge. The decrease of the activation enthalpy for amorphous Ge x Si1-x is similar to the case of crystalline Ge x Si1-x . Possible explanations are discussed.

Interaction of Titanium Atoms with the Surface of Perfect and Defective Carbon Nanotubes

The dispersion of metal atoms over the surface of 1D and 2D carbon systems is the most affordable way to control their properties, which are attractive for many applications in electronics, power engineering, and catalysis. In this work, the features of the interaction of titanium atoms with the surface of carbon nanotubes, caused by various structural defects on these surfaces, were studied by first-principles computer simulation based on the density functional theory. Nanotubes (7, 7) and (11, 0) with similar diameters (≈1 nm) but different types of conductivity, metallic and semiconductor, respectively, were chosen for the study. Three types of defects were studied: a single vacancy, a double vacancy, and a topological defect. Two possible orientations of each type of defect relative to the tube axis were considered. We mainly used the basis of atomic-like orbitals (the SIESTA package) and in some test calculations also the basis of plane waves (the VASP package). Computational experiments have shown that the binding energy of Ti atoms with a defect-free nanotube is always lower than with defective ones, regardless of the used approximation for the exchange-correlation functional (LDA or GGA). The binding energies predicted in the LDA approximation are noticeably higher than in the GGA approximation (up to ~15% for the (7, 7) tube and up to ~50% for the (11, 0) tube). The strongest coupling occurs when the titanium atom is adsorbed on a nanotube with a single vacancy. The resulting configuration can be considered as a defect in the substitution of one carbon by a titanium atom.

Dielectric breakdown and sub-wavelength patterning of monolayer hexagonal boron nitride using femtosecond pulses

Hexagonal boron nitride (hBN) has emerged as a promising two-dimensional (2D) material for many applications in electronics and photonics. Although its linear and nonlinear optical properties have been extensively studied, the interaction of hBN with high-intensity laser pulses, which is important for realizing high-harmonic generation, creating deterministic defects as quantum emitters, and resist-free patterning in this material, has not been investigated. Here we report the first systematic study of dielectric breakdown in chemical vapor deposition (CVD)-grown hBN monolayers induced by single femtosecond laser pulses. We report a breakdown fluence of 0.7 J cm−2, which is at least 7× higher than that of other monolayer 2D materials. A clean removal of hBN without leaving traces behind or causing lateral damage is demonstrated. The ablation features exhibit excellent fidelity with very small edge roughness, which we attribute to its ultrahigh fracture toughness due to its heterogeneous nature with three-fold symmetry. Moreover, even though defects are known to be abundant in CVD-grown hBN, we show experimentally and theoretically that its nonlinear optical breakdown is nearly intrinsic as defects only marginally lower the breakdown threshold. On top of this, we observe that hBN monolayers have a 4–5× lower breakdown threshold than their bulk equivalent. The last two observations can be understood if the carrier generation in monolayers is intrinsically enhanced due to its 2D nature. Finally, we demonstrate laser patterning of array of holes and lines in hBN with sub-wavelength feature sizes. Our work advances the fundamental knowledge of light-hBN interaction in the strong field regime and firmly establishes femtosecond lasers as novel and promising tools for resist-free patterning of hBN monolayers with high fidelity.

Determination of Environmental and Economic Benefits of Graphene-Coated PV Modules Through the School Building

Graphene coatings, which have many applications in electronics and biomedical, show high performance even when applied at a few nanometers thickness, and have also been applied in solar systems. When graphene is applied to the glass surface of photovoltaic (PV) modules, they result in more energy recovery and lower cleaning service fees due to their features such as high permeability, hydrophobic self-cleaning, and low dust retention. In this study, it was determined how much energy gain and CO2 emission reduction could be achieved as a result of graphene-coating on PV modules compared to standard modules, and if PV modules are applied under Turkish conditions, the investment costs, payback period, and return on investment to the user after the payback period was determined. As a result of the calculations, although the initial investment cost of graphene coating is 0.78 %, more than the standard modules, it is concluded that it offers a lower payback period and high return on investment due to the amount of energy it produces, its ability to self-clean, and low dust retention.

Atomic Layer Deposition of ZnO on Mesoporous Silica: Insights into Growth Behavior of ZnO via In-Situ Thermogravimetric Analysis.

ZnO is a remarkable material with many applications in electronics and catalysis. Atomic layer deposition (ALD) of ZnO on flat substrates is an industrially applied and well-known process. Various studies describe the growth of ZnO layers on flat substrates. However, the growth characteristics and reaction mechanisms of atomic layer deposition of ZnO on mesoporous powders have not been well studied. This study investigates the ZnO ALD process based on diethylzinc (DEZn) and water with silica powder as substrate. In-situ thermogravimetric analysis gives direct access to the growth rates and reaction mechanisms of this process. Ex-situ analytics, e.g., N2 sorption analysis, XRD, XRF, HRTEM, and STEM-EDX mapping, confirm deposition of homogenous and thin films of ZnO on SiO2. In summary, this study offers new insights into the fundamentals of an ALD process on high surface area powders.

X-ray Nanospectroscopy Reveals Binary Defect Populations in Sub-micrometric ZnO Crystallites

Besides its many applications in electronics, photonics, and catalysis, ZnO has also been extensively used as the pigment zinc white ever since its introduction in the first half of the 19th century. It is shown here that zinc whites (ZnO formed through zinc vapor oxidation) form a chemically binary system, with each of the sub-micrometric crystallites belonging to either of two distinct classes. The observation of the two classes is done based on X-ray absorption nanospectroscopy and was determined to be caused by differences in the populations of anisotropic crystal defects. A theoretical assessment of the vapor oxidation synthesis method is formulated that predicts that the binary distinction in crystal defect populations is caused by local variations in synthesis parameters. As the crystal defect population in ZnO has been shown to be related to its catalytic properties, these results provide fundamental insights on the link between the intrinsic properties of zinc white and its degradation issues in oil paint.

Recent Advances in 2D MXenes for Photodetection

AbstractA new class of 2D transition metal carbides, carbonitrides and nitrides, termed MXenes, has emerged as a new candidate for many applications in electronics, optoelectronics, and energy storage. Since their first discovery in 2011, MXenes have gathered increasingly more interest owing to their unique physical, chemical, and mechanical properties that can be tuned by different surface terminations and transition metals. In particular, the intriguing optical and electrical properties, including transparency, saturable absorption, and high conductivity, grant MXenes various roles in photodetectors, such as transparent electrodes, Schottky contacts, photoabsorbers, and plasmonic materials. Given the solution‐processability, MXenes also hold great potential for large‐scale synthesis, and thus are favored for a number of electronic and photonic device applications. In this review, recent advances in photodetectors based on 2D MXenes are summarized. Despite the fact that such applications have only recently been explored compared with other 2D materials, MXenes have shown promise in low‐cost and high‐performance photodetection.

Prediction of 2D Li2X (X=Se, Te) monolayer semiconductors by first principles calculations

Abstract Two dimensional monolayer materials play important roles in new generation of electronic and optical devices in nano scale. In this paper, by using first principles calculations, the existence of 2D Li2X (X=Se, Te) monolayer materials are theoretically predicted. Through cohesive energy calculation and phonon dispersion simulation, it is proved that the proposed 2D Li2Se and Li2Te monolayer materials are energetically and dynamically stable suggests their potential experimental realization. Our study shows that these newly predicted compounds are direct semiconductors and have strain tunable wide band gaps. As direct semiconductors, these new monolayers may have many applications in electronics and optoelectronics devices.

2D Li2S monolayer: A global minimum lithium sulfide sandwich

Abstract In this paper, by employing first principles calculations, a two dimensional global minimum structure of Lithium Sulfide (Li2S) was predicted with a wide direct band gap and an inversed sandwich structure 1T-MoS2. The electronic properties investigations reveal that the predicted Li2S monolayer has a strain tunable direct band gap of 3.20 (4.05 eV) computed by PBE (HSE06) theory. As a wide band gap (WBG) semiconductor that is stable at high temperatures, this monolayer may have many applications in electronics and optoelectronics devices. Furthermore, the presence of a narrow phonon band gap between acoustic and optical modes suggests its application in opto-mechanical resonators.

CVD Growth of Monolayer MoS2 on Sapphire Substrates by using MoO3 Thin Films as a Precursor for Co-Evaporation

ABSTRACTScalable synthesis of two-dimensional molybdenum disulfide (MoS2) via chemical vapor deposition (CVD) is of considerable interests for many applications in electronics and optoelectronics. Here, we investigate the CVD growth of MoS2 single crystals on sapphire substrates by using thermally evaporated molybdenum trioxide (MoO3) thin films as molybdenum (Mo) source instead of conventionally used MoO3 powder for co-evaporation synthesis. The MoO3 thin film source provides uniform Mo vapor pressure in the growth chamber resulting in clean and reproducible MoS2 triangles without any oxide or oxysulfide species. Scanning electron microscopy, Raman spectroscopy, photoluminescence spectroscopy and atomic force microscopy characterization were performed to characterize the growth results. Very high photoluminescence (PL) response was observed at 1.85 eV which is a good implication of high optical quality of these crystals directly grown on sapphire substrate.

Preparation of graphene nanoribbons (GNRs) from twisted structure carbon nanotubes using unzipping technique

This work deals with the preparation of graphene nano ribbons (GNRs), which are small bars or strips of graphene with narrow range width less than 50 nm and one atom thick sheet (approximately 140 °A). This material has many applications in electronics, polymer composite, contrast agent bio-imaging and others. This material was prepared from twisted structure of carbon nanotubes CNTs using oxidation process by acids and breaking down by high frequency ultrasonication (sonochemical unzipping). Pre-prepared twisted CNTs were characterized by scanning electron microscope (HRSEM) before treatment. The size, morphology, crystallinity of prepared graphene nanoribbons was also investigated using transmission electron microscope, high resolution transmission electron microscope, and X-ray diffraction and particle size analyzer. The results showed of formation of GNRs with narrow width as lower than 29 nm and uniform sizes. X-ray diffraction reveals Bragg reflections corresponding to the lattice planes (002), (100), (101), (004), and (110) matched with hexagonal system of graphite.

(Invited) Using Surface Chemistry to Direct the Deposition of Nano-objects for Electronics

Nano-objects, including nanowires, nanopores, nanochannels and nanorings, and two-dimensional materials have many applications in electronics, sensing, energy conversion, optoelectronics and non-linear optics. One of the major challenges in the practical use of these structures is their integration into complex functional structures in a predictable and controlled way. In this talk we will describe our progress in synthesizing in situ with precise placement both nano-objects and films of two-dimensional materials, in particular transition metal dichalcogenides. We have introduced two promising new techniques by which to direct the in situ growth of metallic and semiconducting nano-objects. ENDOM, or Electroless Nanowire Deposition On Micropatterned substrates, employs electroless deposition (ELD) to form metallic nanostructures on substrates. SENDOM, or Semiconductor Nanowire Deposition on Micropatterned surfaces, uses chemical bath deposition (CBD) to deposit semiconductor nanowires. Using these processes we demonstate the production of nanowires (diameters < 100 nm), mesowires (100 nm < diameter < ~3000 nm), nanorings, nanopores and nanochannels. These nanostructures can follow complex paths, such as arcs or right-angle bends, and are formed in parallel over cm2 areas. We will also discuss the formation of complex architectures, such as cross-bars, using these methods as well as the electrical properties of metallic nanowires deposited using ENDOM. Two-dimensional materials, such as transition metal dichalcogenides (TMDs), are currently widely sought after for their application in semiconductor and nanoelectronic devices. By using templated substrates such as highly oriented pyrolytic graphite (HOPG) and sapphire we have successfully deposited large area ultra-thin molybdenum disulfide films using CBD. Further we show that the polytype of molybdenum disulfide can be altered between 2H and 1T by depositing the film on substrates with different surface energies. As the surface energy of the substrate is increased the MoS2 deposit changes from 2H to 1T. We also demonstrate that by patterning the substrate with areas of different surface energies that patterned 2H and 1T MoS2 films can be grown in situ.

Effect of Ionic Liquids on the Physical Properties of the Newly Synthesized Conducting Polymer

Conducting polymer has many applications in electronics, optical devices, sensors, and so on; however, there is still a massive scope of improvement in this area. Therefore, towards this aim, in this study, we synthesized a new thiophene-based conducting polymer, 2-heptadecyl-5-hexyl-6-(5-methylthiophen-2-yl)-4-(5-((E)-prop-1-enyl)thiophen-2-yl)-5H-pyrrolo[3,4-d]thiazole (HHMPT). Further, to increase its application, the interactions between the conducting polymer (HHMPT) and ionic liquids (ILs) were investigated by UV-Vis spectroscopy, FTIR spectroscopy, and confocal Raman spectroscopy techniques. Moreover, film roughness and conductivity of the polymer film with or without ILs were also studied. The imidazolium- and ammonium family ILs with the potential to interact with the newly synthesized conducting polymer were used. The results of the interaction studies revealed that the imidazolium family IL-polymer mixtures and ammonium family IL-polymer mixtures have almost similar conductivity at low concentration of ILs. This study provides an insight into the combined effect of a polymer and ILs and may generate many theoretical and experimental opportunities.

Electron velocity saturation and intervalley transfer in monolayer MoS2

Monolayer MoS2 is a material with a rich history and that is being suggested for many applications in electronics, including novel electron devices. Recent experiments has shown that it has a saturation velocity at high electric fields well below other electronic materials such as Si. This is a very important property that is crucial to high performance electron devices. Here, we study this property with ensemble Monte Carlo simulations of the electron transport. We find that the velocity at high electric fields is larger than the experiments, and does not show a saturation up to 100 kV cm−1. In addition, the transport at high fields is dominated by inter-valley transfer to the T valleys.

Stability and properties of PET Films in Electronics Applications in Hygrothermal Environments

ABSTRACTPolyethylene terephthalate (PET) is an interesting flexible substrate material for many applications in electronics since it is inexpensive and has good mechanical and electrical properties. Due to these good properties there is increasing interest in using PET in applications involving harsh environments. However, PET has relatively poor thermal properties, which may cause reliability concerns in demanding conditions. Above its glass transition temperature, Tg, PET is susceptible to hydrolysis, which may considerably restrict its use. Hydrolysis breaks the molecular structure of PET and makes the material mechanically unreliable. This paper reports the reliability of PET films in an LCD display application and in RFID tags in thermal and humid conditions. Additionally, neat PET films were studied. Several thermal cycling and humidity tests were used. The results clearly showed that above the Tg of PET the combined effect of humidity and high temperature caused PET to become brittle leading to considerable reliability problems. However, in dry thermal cycling conditions and in humid conditions below the Tg of PET, the reliability of PET was found to be excellent even under prolonged exposure.

Synthesis and applications of two-dimensional hexagonal boron nitride in electronics manufacturing

In similarity to graphene, two-dimensional (2D) hexagonal boron nitride (hBN) has some remarkable properties, such as mechanical robustness and high thermal conductivity. In addition, hBN has superb chemical stability and it is electrically insulating. 2D hBN has been considered a promising material for many applications in electronics, including 2D hBN based substrates, gate dielectrics for graphene transistors and interconnects, and electronic packaging insulators. This paper reviews the synthesis, transfer and fabrication of 2D hBN films, hBN based composites and hBN-based van der Waals heterostructures. In particular, this review focuses on applications in manufacturing electronic devices where the insulating and thermal properties of hBN can potentially be exploited. 2D hBN and related composite systems are emerging as new and industrially important materials, which could address many challenges in future complex electronics devices and systems.

Energy behaviour for DNA translocation through graphene nanopores

Nanoparticles have considerable promise for many applications in electronics, energy storage, bioscience and biotechnologies. Here we use applied mathematical modelling to exploit the basic principles of mechanics and the 6–12 Lennard-Jones potential function together with the continuum approach, which assumes that a discrete atomic structure can be replaced by an average constant atomic surface density of atoms that is assumed to be smeared over each molecule. We identify a circular hole in a graphene sheet as a nanopore and we consider the molecular interaction energy for both single-strand and double-strand DNA molecules assumed to move through the circular hole in a graphene sheet to determine the radius b of the hole that gives the minimum energy. By minimizing the interaction energy, we observe that the single-strand DNA and double-strand DNA molecules penetrate through a graphene nanopore when the pore radii b> 7.8Å and b> 12.7Å, respectively. Our results can be adopted to offer new applications in the atomic surface processes and electronic sensing.

Voltage biased Varistor-Transistor Hybrid Devices: Properties and Applications

The paper describes the properties and potential applications of a novel hybrid varistor device originating from biased voltage induced modified nonlinear current-voltage (I-V) characteristics. Single crystal of an oxide semiconductor in the family of iron-titanates with the chemical formula of Fe₂TiO₅ (pseudobrookite) has been used as substrate for the varistor. The modifications of the varistor characteristics are achieved by superimposition of a bias voltage in the current path of the varistor. These altered I-V characteristics, when analyzed, reveal the existence of embedded transistors coexisting with the varistor. These transistors exhibit mutual conductance, signal amplification and electronic switching which are the defining signatures of a typical transistor. The tuned varistors also acquire the properties of signal amplification and mutual conductance which expand the range of applications for a varistor beyond its traditional use as circuit protector. Both tuned varistors and the embedded transistors have attributes which make them suitable for many applications in electronics including at high temperatures and for radiation dominated environments such as space.

Voltage biased Varistor-Transistor Hybrid Devices: Properties and Applications

The paper describes the properties and potential applications of a novel hybrid varistor device originating from biased voltage induced modified nonlinear current-voltage (I-V) characteristics. Single crystal of an oxide semiconductor in the family of iron-titanates with the chemical formula of Fe2TiO5 (pseudobrookite) has been used as substrate for the varistor. The modifications of the varistor characteristics are achieved by superimposition of a bias voltage in the current path of the varistor. These altered I-V characteristics, when analyzed, reveal the existence of embedded transistors coexisting with the varistor. These transistors exhibit mutual conductance, signal amplification and electronic switching which are the defining signatures of a typical transistor. The tuned varistors also acquire the properties of signal amplification and mutual conductance which expand the range of applications for a varistor beyond its traditional use as circuit protector. Both tuned varistors and the embedded transistors have attributes which make them suitable for many applications in electronics including at high temperatures and for radiation dominated environments such as space.

Fermi-level pinning, charge transfer, and relaxation of spin-momentum locking at metal contacts to topological insulators

Topological insulators are of interest for many applications in electronics and optoelectronics, but harnessing their unique properties requires detailed understanding and control of charge injection at electrical contacts. Here we present large-scale ab initio calculations of the electronic properties of Au, Ni, Pt, Pd, and graphene contacts to Bi2Se3. We show that regardless of the metal, the Fermi level is located in the conduction band, leading to n-type Ohmic contact to the first quintuplet. Furthermore, we find strong charge transfer and band-bending in the first few quintuplets, with no Schottky barrier for charge injection even when the topoplogical insulator is undoped. Our calculations indicate that Au and graphene leave the spin-momentum locking mostly unaltered, but on the other hand, Ni, Pd, and Pt strongly hybridize with Bi2Se3 and relax spin-momentum locking. Our results indicate that judicious choice of the contact metal is essential to reveal the unique surface features of topological insulators.