Showing papers in "Journal of Electronic Materials in 2018"

Label Free Detection of Biomolecules Using Charge-Plasma-Based Gate Underlap Dielectric Modulated Junctionless TFET

Abstract: Nanoscale devices are emerging as a platform for detecting biomolecules. Various issues were observed during the fabrication process such as random dopant fluctuation and thermal budget. To reduce these issues charge-plasma-based concept is introduced. This paper proposes the implementation of charge-plasma-based gate underlap dielectric modulated junctionless tunnel field effect transistor (DM-JLTFET) for the revelation of biomolecule immobilized in the open cavity gate channel region. In this p+ source and n+ drain regions are introduced by employing different work function over the intrinsic silicon. Also dual material gate architecture is implemented to reduce short channel effect without abandoning any other device characteristic. The sensitivity of biosensor is studied for both the neutral and charge-neutral biomolecules. The effect of device parameters such as channel thickness, cavity length and cavity thickness on drain current have been analyzed through simulations. This paper investigates the performance of charge-plasma-based gate underlap DM-JLTFET for biomolecule sensing applications while varying dielectric constant, charge density at different biasing conditions.

Sol–Gel Synthesis of Fe-Doped TiO 2 Nanocrystals

Abstract: Fe-doped TiO2 powders were synthesized by the sol–gel method using titanium (IV) isopropoxide (TTIP) as the starting material, ethanol as solvent, and ethylene glycol (EG) as stabilizer. These prepared samples were characterized by x-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), Fourier-transform infrared (FTIR) spectroscopy, diffuse reflection spectroscopy (DRS), energy-dispersive x-ray spectroscopy (EDX), and photoluminescence (PL) analyses to study their structure, morphology, and optical properties. The particle size of Fe-doped TiO2 was in the range of 18–39 nm and the minimum crystallite size was achieved for 4 mol.% of Fe. The XRD result of the samples that were doped with Fe showed a tetragonal structure. It also revealed the coexistence of the anatase and rutile phases, and showed that their ratio changed with various molar concentrations of Fe dopant. FTIR spectroscopy showed the presence of the Ti-O vibration band in the samples. PL analysis revealed the PL property in the UV region. Visible irradiation and the intensity of PL spectra were both reduced by doping TiO2 with 3 mol.% of Fe as compared to the pure variety. The spectra from the DRS showed a red shift and a reduction of 2.6 eV in the band gap energy for 4 mol.% Fe-doped TiO2. The optimum level of impurity (4 mol.%) for Fe-doped TiO2 nanoparticles (NPs), which improve the optical and electrical properties by using new precursors and can be used in solar cells and electronic devices, was determined. The novelty of this work consists of: the Fe/TiO2 NPs are synthesized by new precursors from sol–gel synthesis of iron and TTIP using acetic acid-catalyzed solvolysis (original idea) and the optical properties optimized with a mixture of phases (anatase/rutile) of Fe-doped TiO2 by this facile method.

Elastic, Optoelectronic and Thermoelectric Properties of the Lead-Free Halide Semiconductors Cs 2 AgBi X 6 ( X = Cl, Br): Ab Initio Investigation

Abstract: We report a detailed investigation of the elastic moduli, electronic band structure, density of states, chemical bonding, electron and hole effective masses, optical response functions and thermoelectric properties of the lead-free halide double perovskites Cs2AgBiCl6 and Cs2AgBiBr6 using the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA-PBEsol) and the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. Because of the presence of heavy elements in the studied compounds, we include the spin–orbit coupling (SOC) effect. Our calculated structural parameters agree very well with the available experimental and theoretical findings. Single-crystal and polycrystalline elastic constants are predicted using the total-energy versus strain approach. Three-dimensional representations of the crystallographic direction dependence on the shear modulus, Young’s modulus and Poisson’s ratio demonstrate a noticeable elastic anisotropy. The TB-mBJ potential with SOC yields an indirect band gap of 2.44 (1.93) eV for Cs2AgBiCl6 (Cs2AgBiBr6), in good agreement with the existing experimental data. The chemical bonding features are probed via density of states and valence electron density distribution calculations. Optical response functions were predicted from the calculated band structure. Both of the investigated compounds have a significant absorption coefficient (∼ $$ 25 \times 10^{4} \;{\hbox{cm}}^{ - 1} $$ ) in the visible range of sunlight. The thermoelectric properties of the title compounds were investigated using the FP-LAPW approach in combination with the semi-classical Boltzmann transport theory. The Cs2AgBiCl6 and Cs2AgBiBr6 compounds have a large thermopower S, which makes them potential candidates for thermoelectric applications.

XPS Spectra Analysis of Ti 2+ , Ti 3+ Ions and Dye Photodegradation Evaluation of Titania-Silica Mixed Oxide Nanoparticles

Abstract: TiO2-SiO2 mixed oxides have been prepared by the sol–gel technique from tetrabutyl orthotitanate and tetraethyl orthosilicate. The prepared materials were characterized by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, nitrogen physisorption, Fourier-transform infrared spectroscopy (FT-IR) and x-ray photoelectron spectroscopy (XPS). The results indicate that the TiO2-SiO2 mixed oxides have a large surface area and a nanoscale size. FT-IR spectra show that Ti atoms are bonded to silica by oxygen bridging atoms in Ti-O-Si bonds. The titanium valence states in TiO2-SiO2 mixed oxides were investigated by XPS, and their spectra report the presence of Ti2+ and Ti3+ cations for high silica concentration, suggesting the formation of oxygen vacancies. The photocatalytic activity of the prepared materials has been evaluated for the photodegradation of methylene blue (MB). The mixed oxides were activated by means of a UV light source, and the concentration of MB was monitored by UV–Vis spectroscopy. The synthesized TiO2-SiO2 shows significantly higher MB removal efficiency in comparison with that of the commercial TiO2 Degussa, P25. In this paper, we observed three valence states of titanium: Ti4+, Ti3+ and Ti2+ in TiO2-SiO2 40%. This issue has not yet been reported. XPS analysis show that the content of Ti2+ and Ti3+ amounts to 25.26 at.% and 13.08 at.%, respectively, while the concentration of Ti4+ is 61.72 at.%, much lower than in the TiO2-SiO2 9% sample. This behavior is explained observing that in TiO2-SiO2 40%, Ti4+ is reduced to Ti3+ and Ti2+ to a larger extent with respect to TiO2-SiO2 9%.

A Hydrothermal Route to the Synthesis of CaTiO 3 Nanocuboids Using P25 as the Titanium Source

Abstract: CaTiO3 nanocuboids (width 0.3–0.5 μm, length 0.8–1.1 μm) have been synthesized by a hydrothermal route using commercial P25 as the titanium source. The as-prepared sample was systematically characterized by means of x-ray powder diffraction, field-emission scanning electron microscopy, field-emission transmission electron microscopy, x-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, ultraviolet–visible diffuse reflectance spectroscopy and electrochemical impedance spectroscopy. The photocatalytic activity of the sample was evaluated by degrading rhodamine B under simulated sunlight irradiation. It is demonstrated that CaTiO3 nanocuboids exhibit superior photocatalytic activity when compared with CaTiO3 nanoparticles. By investigating the effect of scavengers on the dye degradation and the yield of hydroxyl (·OH) radicals, it is concluded that ·OH is the dominant reactive species.

Ultra-Thin Dual-Band Polarization-Insensitive and Wide-Angle Perfect Metamaterial Absorber Based on a Single Circular Sector Resonator Structure

Abstract: We present a simple design for an ultra-thin dual-band polarization-insensitive and wide-angle perfect metamaterial absorber (PMMA) based on a single circular sector resonator structure (CSRS). Both simulation and experimental results reveal that two resonance peaks with average absorption above 99% can be achieved. The dual-band PMMA is ultra-thin with total thickness of 0.5 mm, which is

Green Synthesis and Characterization of SmVO 4 Nanoparticles in the Presence of Carbohydrates As Capping Agents with Investigation of Visible-Light Photocatalytic Properties

Abstract: SmVO4 nanoparticles were synthesized through a fast and simple procedure (green method). The effects of three parameters including temperature, type of capping agent, and concentration on the size and morphology behavior of SmVO4 nanoparticles were explored. The analysis of SmVO4 nanoparticles was performed through some techniques including, Fourier transform infrared spectroscopy, x-ray diffraction, energy dispersive x-ray microanalysis, scanning electron microscopy, transmission electron microscopy, thermogravimetry, differential thermal analysis, ultraviolet–visible spectroscopy, and vibrating sample magnetometers. The study of photocatalytic behaviour of the SmVO4 nanoparticles in various conditions has been carried out. The impacts of different factors such as dosage, grain size, and kind of pollutant (methylene blue = MB and methyl orange = MO) on the photocatalytic property of SmVO4 nanoparticles were assessed. The photocatalytic activities of SmVO4 catalysts were studied for the degradation of dye under visible light (λ > 400 nm).

A Resonant Tunneling Nanowire Field Effect Transistor with Physical Contractions: A Negative Differential Resistance Device for Low Power Very Large Scale Integration Applications

Abstract: In this paper, the influence of ultra-scaled physical symmetrical contraction on electrical characteristics of ultra-thin silicon-on-insulator nanowires with circular gate-all-around structure is investigated by using a 3D Atlas numerical quantum simulator based on non-equilibrium green’s function formalism. It is demonstrated that local cross-section variation in a nanowire transistor results in the establishment of tunnel energy barriers at the source-channel and drain-channel junctions which change device physics and cause a transmission from a quantum wire (1-D) to a floating quantum dot nanowire (0-D) introducing a resonant tunneling nanowire FET (RT-NWFET) as an interesting concept of nanoscale MOSFETs. The barriers construct resonance energy levels in the channel region of nanowires because of the longitudinal confinement in three directions causing some fluctuation in I D–V GS characteristic. In addition, these barriers remarkably improve the subthreshold swing and minimize the ON/OFF-current ratio degradation at a low operation voltage of 0.5 V. As a result, RT-NWFETs are intrinsically preserved from drain–source tunneling and are an interesting candidate for developing the roadmap below 10 nm.

Tuning the Electronic Properties, Effective Mass and Carrier Mobility of MoS 2 Monolayer by Strain Engineering: First-Principle Calculations

Abstract: In this paper, we studied the electronic properties, effective masses, and carrier mobility of monolayer $$\hbox {MoS}_2$$ using density functional theory calculations. The carrier mobility was considered by means of ab initio calculations using the Boltzmann transport equation coupled with deformation potential theory. The effects of mechanical biaxial strain on the electronic properties, effective mass, and carrier mobility of monolayer $$\hbox {MoS}_2$$ were also investigated. It is demonstrated that the electronic properties, such as band structure and density of state, of monolayer $$\hbox {MoS}_2$$ are very sensitive to biaxial strain, leading to a direct–indirect transition in semiconductor monolayer $$\hbox {MoS}_2$$ . Moreover, we found that the carrier mobility and effective mass can be enhanced significantly by biaxial strain and by lowering temperature. The electron mobility increases over 12 times with a biaxial strain of 10%, while the carrier mobility gradually decreases with increasing temperature. These results are very useful for the future nanotechnology, and they make monolayer $$\hbox {MoS}_2$$ a promising candidate for application in nanoelectronic and optoelectronic devices.

Linear and Nonlinear Optics of CBD Grown Nanocrystalline F Doped CdS Thin Films for Optoelectronic Applications: An Effect of Thickness

Abstract: Fluorine (F) doped (i.e. 1 wt.%) cadmium sulfide (CdS) thin films with different thicknesses were fabricated on fluorine doped tin oxide coated glass substrates by chemical bath deposition methods. For doping of F, 1 wt.% ammonium fluoride was added into the solution. A significant influence of thicknesses on physical properties of F doped CdS thin films was observed. The thin films were investigated by various characterization techniques such as x-ray diffraction (XRD), UV–Vis–NIR, FT-Raman spectroscopy and scanning electron microscope. XRD analysis showed that the films are preferentially grown along (111) plane. The crystallites’ size changed with increases the film’s thickness. Films showed high transmittance in visible region. Raman spectra showed shift in first and second longitudinal phonon vibration (1LO and 2LO) with the change in thickness of the films. This shows that changing thickness leads to changes in the physical properties of films. The values of the band gaps were estimated as 2.60 eV, 2.75 eV, 2.80 eV for films of thickness 100 nm, 150 nm and 200 nm, respectively. Hence, the band gap of films increases with an increase in thickness. Refractive index, linear optical susceptibility, nonlinear optical susceptibility and nonlinear refractive index were also estimated. The higher values of nonlinear optical parameters shows good scope in nonlinear optical applications.

Efficiency Enhancement of CH 3 NH 3 SnI 3 Solar Cells by Device Modeling

Abstract: Lead halide perovskite solar cells (LHPSC) have great potential, with conversion efficiency exceeding 20%. However, their toxic nature and difficult fabrication prevent their consideration for commercial applications. To address this, numerical analysis was performed to propose a structure for lead-free perovskite solar cells with MASnI3 as absorber layer. Device modeling for Cd1−xZnxS as electron transport layer (ETL) and methylamine tin halide as hole transport layer (HTL) was carried out using a solar cell capacitance simulator. The simulation results revealed the dependence of the open-circuit voltage (VOC), short-circuit current (JSC), fill factor (FF), and power conversion efficiency on the HTL valence-band offset, absorber layer thickness, absorber layer doping concentration, ETL band offset, minority-carrier diffusion length, and defects at the HTL–absorber and absorber–ETL interfaces. An optimum absorber layer thickness was confirmed, being well consistent with the range for practical absorber layer designs. Moreover, conversion efficiency of 18.71% was found for absorber thickness of 500 nm and doping concentration of 1 × 1016 cm−3. These results will provide important guidelines for design of low-cost perovskite solar cells.

Ab Initio Investigation of the Structural, Electronic and Optical Properties of the Li 2 In 2 XY 6 (X = Si, Ge; Y = S, Se) Compounds

Abstract: The structural, electronic and optical properties of the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds, which are scarcely studied by theoretical methods previously, have been investigated by ab initio calculations based on the density functional theory (DFT) in this article by using the full potential linearized augmented plane wave method The equilibrium structural ground state properties of the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds such as the lattice parameters were obtained from the structural optimization process (with the Perdew–Burke–Ernzerhof generalized gradient approximation), and they are in close agreement with the experimental lattice parameters Conversely, calculations by the modified Becke Johnson exchange potential indicates that the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds are semiconductors with direct energy band gaps It is clearly observed from the DFT-calculated partial density of states, that there are significant contributions of the S-s and S-p states in the Li2In2SiS6 and Li2In2GeS6 compounds as well as the Se-s and Se-p states in the Li2In2SiSe6 and Li2In2GeSe6 compounds, respectively The calculated band gaps ranging from 192 eV to 324 eV of the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds are in good agreement with the experimental results, where the calculated band gap values are positioned in the visible region of the electromagnetic spectrum; therefore, these materials can be efficiently used for opto-electronic and optical applications Furthermore, some general trends are observed in the optical responses of the compounds, which are possibly correlated to the energy band gaps when the X cations changes from Si to Ge and the Y anions changes from S to Se in the Li2In2XY6 (X = Si, Ge; Y = S, Se) compounds, respectively

Strong Visible Light Photocatalytic Activity of Magnetically Recyclable Sol–Gel-Synthesized ZnFe 2 O 4 for Rhodamine B Degradation

Abstract: Visible light-responsive ZnFe2O4 photocatalyst with a spinel structure was synthesized via a sol-gel method. The visible light photocatalysis of ZnFe2O4 was investigated by decomposing Rhodamine B (RhB) solution. Under ∼30 min of visible light irradiation, the decomposition ratio of RhB is up to ∼97.4%. The excellent photocatalytic performance of ZnFe2O4 photocatalyst is attributed to the high effective oxidation–reduction reaction caused by light irradiation excitation. With the increase of decomposition time, the wavelength of the maximum absorption peak of RhB solutions shifts from 557 nm to 498 nm (“blue shift”), which is because of the N-deethylation and cleavage of the conjugated chromophore structure of RhB. ZnFe2O4 photocatalyst also exhibits a weak ferromagnetism performance. The decomposition ratio of RhB for the magnetically recycled ZnFe2O4 is ∼94.6%. Strong visible light photocatalysis and convenience of magnetic recycling make ZnFe2O4 promising for photocatalytic applications in dye wastewater treatment.

Structural, Optical and Electrical Properties of ITO Thin Films

Abstract: Transparent and conductive thin films of indium tin oxide were fabricated on glass substrates by the thermal evaporation technique. Tin doped indium ingots with low tin content were evaporated in vacuum (1.33 × 10−7 kpa) followed by an oxidation for 15 min in the atmosphere in the temperature range of 600–700°C. The structure and phase purity, surface morphology, optical and electrical properties of thin films were studied by x-ray diffractometry and Raman spectroscopy, scanning electron microcopy and atomic force microscopy, UV–visible spectrometry and Hall measurements in the van der Pauw configuration. The x-ray diffraction study showed the formation of the cubical phase of polycrystalline thin films. The morphological analysis showed the formation of ginger like structures and the energy dispersive x-ray spectrum confirmed the presence of indium (In), tin (Sn) and oxygen (O) elements. Hall measurements confirmed n-type conductivity of films with low electrical resistivity (ρ) ∼ 10−3 Ω cm and high carrier concentration (n) ∼ 1020 cm−3. For prevalent scattering mechanisms in the films, experimental data was analyzed by calculating a mean free path (L) using a highly degenerate electron gas model. Furthermore, to investigate the performance of the deposited films as a transparent conductive material, the optical figure of merit was obtained for all the samples.

Effectuality of Barrier Height Inhomogeneity on the Current–Voltage–Temperature Characteristics of Metal Semiconductor Structures with CdZnO Interlayer

Abstract: Current-conduction/transport mechanisms (CCMs or CTMs) through barrier and barrier height (BH) formation in the Al/(CdZnO)/p-Si/Al diodes, which were prepared by the sol–gel method, were examined in the range of 110–380 K. The decrease of zero-bias BH (ΦBo) and increase of ideality factor (n) with decreasing temperature were observed. The classic Richardson plot indicated two distinct linear regions that correspond to low and high temperature range (LTR and HTR), respectively. Contrary to this, the acquired Richardson constant value (A*) was much lower than its theoretical value (32 A cm−2 K−2). Such abnormal behavior of the ΦBo, n and A* was attributed to the evidence of the barrier inhomogeneities, especially at low temperature. Therefore, the ΦBo−n, ΦBo and (n−1 − n) versus q/2kT plots were sketched to acquire significant clues for the Gaussian distribution (GD) of the BHs at rectifier contact area with the mean BH ( $$ \bar{\Phi }_{\rm{Bo}} $$ ) and standard deviation (σso), which also have two linear parts with distinct slopes. $$ \bar{\Phi } $$ and σso were calculated from the slope and intercept of ΦBo versus q/2kT plot as 0.802 eV and 0.066 V for LTR, 1.043 eV and 0.106 V for HTR, respectively. The $$ \bar{\Phi }_{\rm{Bo}} $$ and A* were acquired by utilizing the σso values and using the Richardson plot as 0.626 eV and 14.26 A cm−2 K−2 for LTR and 1.021 eV and 32.53 A cm−2 K−2 for HTR, respectively. Thus, the I–V–T characteristics of the Al/(CdZnO)/p-Si/Al diodes at forward biases were successfully elucidated by the double-GD of BHs with mean BHs of 0.626 eV and 1.021 eV, respectively.

Magnetodielectric Microwave Radiation Absorbent Materials and Their Polymer Composites

Abstract: Functional radiation absorbent materials (RAMs) can transform incident microwave energy into heat energy, hence being essential to impede reflections of microwaves generated by modern radars in military, aerospace, and commercial applications. For such applications, use of composites is imperative to maintain an optimum bandwidth, enhance the magnetoelectric functional activity, ensure a flexible design, and reduce weight, which can be achieved by tuning the volume fractions of such materials. Use of ferrites is widely recommended for microwave (MW) suppression due to their appropriate magnetodielectric characteristics. This review first describes the requirements for an ideal MW absorber and accurate measurements for quantification of MW absorption. Then, the significance, applications, approaches, and experimental developments of magnetodielectric polymer composite RAMs are presented. Moreover, such composites facilitate exploration of nanoscale functional properties to achieve efficient RAMs. The permeability and permittivity at microwave frequencies, magnetic properties induced by unique elemental doping mechanisms, as well as physical and chemical properties of these composites are also presented. The resonance-dependent absorption condition for different families of magnetic ferrites, as well as the dependence of their magnetic properties on the resonant frequency and their absorption bandwidth (spinels up to 30 GHz, hexaferrites 1 GHz to 100 GHz), are presented for applications. Furthermore, magnetodielectric composites decorated with carbon fillers (carbon nanotubes/multiwall carbon nanotubes, graphene, reduced graphene oxide, etc.) with enhanced microwave absorption properties are discussed. Additionally, core–shell magnetodielectric materials are also discussed in detail. Finally, this review highlights the importance of magnetodielectric polymer composites decorated with conducting materials and core–shell magnetodielectric materials as effective broadband RAMs achieving the primary application requirement of broadband absorption of at least −10 dB with reduced thickness.

Cu-Sn Intermetallic Compound Joints for High-Temperature Power Electronics Applications

Abstract: Cu-Sn solid–liquid interdiffusion (SLID) bonded joints were fabricated using a Sn-Cu solder paste and Cu for high-temperature power electronics applications. The interfacial reaction behaviors and the mechanical properties of Cu6Sn5 and Cu3Sn SLID-bonded joints were compared. The intermetallic compounds formed at the interfaces in the Cu-Sn SLID-bonded joints significantly affected the die shear strength of the joint. In terms of thermal and mechanical properties, the Cu3Sn SLID-bonded joint was superior to the conventional solder and the Cu6Sn5 SLID-bonded joints.

3D Printing of NinjaFlex Filament onto PEDOT:PSS-Coated Textile Fabrics for Electroluminescence Applications

Abstract: Electroluminescence (EL) is the property of a semiconductor material pertaining to emitting light in response to an electrical current or a strong electric field. The purpose of this paper is to de ...

Current-Transport Mechanisms of the Al/(Bi 2 S 3 -PVA Nanocomposite)/p-Si Schottky Diodes in the Temperature Range Between 220 K and 380 K

Abstract: In this research, bismuth sulfide nanostructures were prepared in the presence of polyvinyl alcohol (PVA) as a capping agent by an ultrasound-assisted method The x-ray diffraction results show the crystalline phase of the sample and the mean crystalline size estimated by Debye–Scherer’s equation The UV–Vis absorption spectrum show that the optical absorbance edge of Bi2S3 nanostructure was blue-shifted The Fourier transform infrared spectra confirm the presence of PVA in the sample and transmission electron microscopy imaging shows that the structures are in nanoscale The semi-logarithmic forward bias I–V plots have two distinct linear regimes for each temperature which are called low- and moderate-bias regions (LBR and MBR) In order to effectively interpret possible current-conduction/transport mechanisms, the reverse saturation current (Io), ideality factor (n) and zero-bias barrier height (ΦBO) were obtained from the slope and intercept of these plots and they were found to be a strong function of temperature and voltage The high value of n even at high temperature and the increase of ΦBO with increasing temperature for the two regions is clear evidence of the deviation from thermionic emission (TE) theory Therefore, ΦBO versus n and q/2kT plots were drawn to get evidence of the Gaussian distribution (GD) of the barrier height (BH) and they show a linear behavior The mean values of BH ( $$ \bar{\Phi }_{\rm{BO}} $$ ) and standard deviation (σs) were also obtained from the intercepts and slopes of the ΦBO versus q/2kT plots as 144 eV and 019 V for the LBR and 132 eV and 018 V for the MBR, respectively After that, the values $$ \bar{\Phi }_{\rm{BO}} $$ and effective Richardson constant (A*) were obtained as 129 eV and 2676 A/(cm K)2 for the LBR and 127 eV and 2817 A/(cm K)2 for the MBR, respectively Such non-ideal I–V–T characteristics for the Al/(PVA-Bi2S3)/p-Si structure can be successfully explained by the single GD of BH for the LBR and MBR

Effect of Post-annealing on the Electrochromic Properties of Layer-by-Layer Arrangement FTO-WO 3 -Ag-WO 3 -Ag

Abstract: In the current study, composites of tungsten trioxide (W03) and silver (Ag) are deposited in a layer-by-layer electrochromic (EC) arrangement onto a fluorine-doped tin oxide coated glass substrate. Tungsten oxide nanoparticles are an n-type semiconductor that can be used as EC cathode material. Nano-sized silver is a metal that can serve as an electron trap center that facilitates charge departure. In this method, the WO3 and Ag nanoparticle powder were deposited by physical vapor deposition onto the glass substrate. The fabricated electrochromic devices (ECD) were post-annealed to examine the effect of temperature on their EC properties. The morphology of the thin film was characterized by scanning electron microscopy and atomic force microscopy. Structural analysis showed that the addition of silver dopant increased the size of the aggregation of the film. The film had an average approximate roughness of about 17.8 nm. The electro-optical properties of the thin film were investigated using cyclic voltammetry and UV–visible spectroscopy to compare the effects of different post-annealing temperatures. The ECD showed that annealing at 200°C provided better conductivity (maximum current of about 90 mA in the oxidation state) and change of transmittance (ΔT = 90% at the continuous switching step) than did the other thin films. The optical band gaps of the thin film showed that it allowed direct transition at 3.85 eV. The EC properties of these combinations of coloration efficiency and response time indicate that the WO3-Ag-WO3-Ag arrangement is a promising candidate for use in such ECDs.

Parametric Study of Solder Flux Hygroscopicity: Impact of Weak Organic Acids on Water Layer Formation and Corrosion of Electronics

Abstract: The presence of solder flux residues on the printed circuit board assembly surface is an important factor contributing to humidity-related reliability issues that affect device lifetime. This investigation focuses on understanding the hygroscopic nature of typical wave solder flux activators—weak organic acids—under varied temperature conditions. In situ x-ray diffraction measurements assessed the effect of high temperature on the crystal structure of organic activators. The hygroscopicity studies were carried out under relative humidity (RH) levels varying from 30% to ∼ 99% and at temperatures 25°C, 40°C, and 60°C. Water absorption levels were determined using the gravimetric method, and the influence on reliability was assessed using electrochemical impedance and leak current measurements performed on the surface insulation resistance comb patterns. The corrosion studies were correlated with the hygroscopicity results and solubility data. Corrosion morphology was analysed using the optical microscopy and scanning electron microscopy. The results show that the hygroscopic nature of typical solder flux residue depends on its chemical structure and temperature. An increase of temperature shifts the critical RH level for water vapour absorption towards lower RH range, accelerating the formation of a conductive electrolyte and the occurrence of ion transport-induced electrochemical migration. The overall ranking of flux activators with the increasing order of aggressivity is: palmitic < suberic < adipic < succinic < glutaric < dl-malic acid.

An Asymmetric Supercapacitor with Mesoporous NiCo 2 O 4 Nanorod/Graphene Composite and N-Doped Graphene Electrodes

Abstract: In the present work, mesoporous NiCo2O4 nanorod/graphene oxide (NiCo2O4/GO) composite was prepared by a facile and cost-effective hydrothermal method and meanwhile, N-doped graphene (N-G) was fabricated also by a hydrothermal synthesis process. NiCo2O4/GO composite and N-G were used as positive and negative electrodes for the supercapacitor, respectively, which all displayed excellent electrochemical performances. The NiCo2O4/GO composite electrode exhibited a high specific capacitance of 709.7 F g−1 at a current density of 1 A g−1 and excellent rate capability as well as good cycling performance with 84.7% capacitance retention at 6 A g−1 after 3000 cycles. A high-voltage asymmetric supercapacitor (ASC) was successfully fabricated using NiCo2O4/GO composite and N-G as the positive and negative electrodes, respectively, in 1 M KOH aqueous electrolyte. The ASC delivered a high energy density of 34.4 Wh kg−1 at a power density of 800 W kg−1 and still maintained 28 Wh kg−1 at a power density of 8000 W kg−1. Furthermore, this ASC showed excellent cycling stability with 94.3% specific capacitance retained at 5 A g−1 after 5000 cycles. The impressive results can be ascribed to the positive synergistic effects of the two electrodes. Evidently, our work provides useful information for assembling high-performance supercapacitor devices.

Effect of Shock Waves on Dielectric Properties of KDP Crystal

Abstract: An alternative non-destructive approach is proposed and demonstrated for modifying electrical properties of crystal using shock-waves. The method alters dielectric properties of a potassium dihydrogen phosphate (KDP) crystal by loading shock-waves generated by a table-top shock tube. The experiment involves launching the shock-waves perpendicular to the (100) plane of the crystal using a pressure driven table-top shock tube with Mach number 1.9. Electrical properties of dielectric constant, dielectric loss, permittivity, impedance, AC conductivity, DC conductivity and capacitance as a function of spectrum of frequency from 1 Hz to 1 MHz are reported for both pre- and post-shock wave loaded conditions of the KDP crystal. The experimental results reveal that dielectric constant of KDP crystal is sensitive to the shock waves such that the value decreases for the shock-loaded KDP sample from 158 to 147. The advantage of the proposed approach is that it is an alternative to the conventional doping process for tailoring dielectric properties of this type of crystal.

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

Abstract: The present work offers both a complete, quantitative model and a conservative acceleration factor expression for the life span of SnAgCu solder joints in thermal cycling. A broad range of thermal cycling experiments, conducted over many years, has revealed a series of systematic trends that are not compatible with common damage functions or constitutive relations. Complementary mechanical testing and systematic studies of the evolution of the microstructure and damage have led to a fundamental understanding of the progression of thermal fatigue and failure. A special experiment was developed to allow the effective deconstruction of conventional thermal cycling experiments and the finalization of our model. According to this model, the evolution of damage and failure in thermal cycling is controlled by a continuous recrystallization process which is dominated by the coalescence and rotation of dislocation cell structures continuously added to during the high-temperature dwell. The dominance of this dynamic recrystallization contribution is not consistent with the common assumption of a correlation between the number of cycles to failure and the total work done on the solder joint in question in each cycle. It is, however, consistent with an apparent dependence on the work done during the high-temperature dwell. Importantly, the onset of this recrystallization is delayed by pinning on the Ag3Sn precipitates until these have coarsened sufficiently, leading to a model with two terms where one tends to dominate in service and the other in accelerated thermal cycling tests. Accumulation of damage under realistic service conditions with varying dwell temperatures and times is also addressed.

Bandgap Tuning of Sm and Co Co-doped BFO Nanoparticles for Photovoltaic Application

Abstract: Multiferroic $$BiFeO_3$$ (BFO) with bandgap energy ( $$E_g$$ ) between 2.2 eV to 2.7 eV is a potential candidate for photovoltaic (PV) application. However, the efficiency of BFO based PV solar cells is reportedly still too low (less than 2%) to be used for practical applications. Reducing $$E_g$$ of BFO without compromising the ferroelectric properties is a big challenge to the scientific community to obtain power conversion efficiencies beyond the maximum value of 26.6% reported in general for silicon based hetero-structure PV solar cells. In this context, samarium (Sm) and cobalt (Co) co-doped BFO ( $$Bi_{0.9}Sm_{0.1}Fe_{0.9}Co_{0.1}O_3$$ ) nanoparticles were synthesized using the sol-gel method. X-ray diffractometry was employed to determine the structure of synthesized nanoparticles. A well-defined crystalline structure of co-doped BFO nanoparticles was confirmed. Field emission scanning electron microscopy was carried out to study grain morphology of synthesized nanoparticles. Sm and Co dopants have been shown to reduce grain size significantly from 68.3 nm to 18.5 nm. An UV-Vis-NIR spectrophotometer was used to measure diffuse reflectance to calculate $$E_g$$ . A significant reduction of $$E_g$$ down to 1.50 eV of co-doped BFO compared to undoped and or single doped counterpart has been manifested.

Ruthenium(II) Complex Based Photodiode for Organic Electronic Applications

Abstract: In this study, the electrical and photoresponse properties of a photovoltaic device with Ruthenium(II) complex interfacial thin film were investigated. Heteroleptic Ru(II) complex including bidentate and tridentate ligands thin film was coated on n-Si substrate by the spin coating technique. From current–voltage (I–V) measurements of an Au/Ru(II)/n-Si photodiode, it is observed that the reverse bias current under light is higher than that of the current in the dark. This indicates that the photodiode exhibits a photoconducting characteristic. The transient measurements such as photocurrent, photocapacitance and photoconductance were performed under various illumination conditions. These measurements indicate that the photodiode has a high photoresponsivity. The electrical parameters such as barrier height (Φb), ideality factor (n) and series resistance (R s) of the photodiode were determined from the analysis of I–V characteristics. Moreover, the capacitance/conductance–voltage characteristics of the photodiode highly depend on both voltage and frequency. Results show that the heterojunction can be used for various optoelectronic applications.

Effects of Zn and Ga Additions to Suppress PdSn 4 Growth at a Solder/Pd Interface Under Current Stressing

Abstract: PdSn4 is the major phase formed in the interfacial systems of Pd with lead-free solders. In this study, we examined the interfacial behaviors of the Sn/Pd/Sn system under current stressing of 5000 A/cm2 at 180°C. The results revealed that the electromigration effect on the PdSn4 was insignificant. However, the PdSn4 growth was very fast, similar to that without current stressing. The thickness of the PdSn4 layer was ∼44 μm after only 6 h of current stressing, and further increased to be ∼83 μm after a 24-h test. The PdSn4 phase had a superior electromigration-resistance, but the fast growth was a major concern for the interfacial reliability of the solder joints. To suppress the PdSn4 growth, minor amounts of Zn or Ga were added into the Sn-based solder to investigate the solder/Pd couples under current stressing. Remarkably, only minor 0.5 wt.%Zn addition effectively inhibited the PdSn4 growth under current stressing. After 6 h of current stressing, the thickness of the PdSn4 layer was reduced to ∼17 μm. In addition, minor Ga addition had a similar inhibiting effect. In the Sn-0.5 wt.%Ga/Pd couple, the PdSn4 layer was only ∼12 μm thick even after current stressing of 24 h. The inhibiting effects of Zn and Ga on the PdSn4 growth under current stressing and the related possible reasons are further discussed.

Enhanced Thermoelectric Performance of n -type Bi 2 O 2 Se Ceramics Induced by Ge Doping

Abstract: Ceramic samples with the composition Bi2−x Ge x O2Se1.01 (x = 0, 0.05, 0.075, and 0.1) were synthesized by solid-state reaction and compacted using a hot-pressing technique. The prepared materials were characterized by x-ray diffraction analysis, electron microscopy, and measurements of electrical conductivity σ, Seebeck coefficient S, and thermal conductivity in the temperature range 300–780 K. Ge in the Bi2O2Se host structure led to an increase of the free electron concentration compared to pristine Bi2O2Se1.01. The donor effect is attributed to point substitutional defects in the Bi sublattice— $$ {\hbox{Ge}}_{\rm{Bi}}^{ + }$$ , and oxygen vacancies $$ {\hbox{V}}_{\rm{O}}^{ + 2}$$ producing free electrons. As a result, we observe an increase in the electrical conductivity and decrease in Seebeck coefficient while thermal conductivity κ changes slightly. The highest value of the dimensionless figure of merit ZT = σS 2 T/κ reaches 0.25 for the composition Bi1.95Ge0.05O2Se1.01 at T = 723 K, which is, to date, the highest ZT value reported for Bi2O2Se ceramics. Our results suggest that Bi2O2Se is still worth exploring.

Investigation of Zinc Oxide-Loaded Poly(Vinyl Alcohol) Nanocomposite Films in Tailoring Their Structural, Optical and Mechanical Properties

Abstract: Wurtzite ZnO nanoparticles, as a nanofiller, were incorporated in a poly(vinyl alcohol) (PVA) matrix to prepare multipurpose nanocomposite films using a solution casting approach. Some advanced analytical techniques were used to investigate the properties of prepared nanocomposite films. The mediation of ZnO nanofillers resulted in modification of structural, optical and mechanical properties of nanocomposite films. A comprehensive band structure investigation might be useful for designing technological applications like in optoelectronic devices. The experimental results were found to be closely dependent on the nanofiller contents. Some theoretical models like Tauc’s and Wemple–DiDomenico, were employed to investigate the band structure parameters. The imaginary part of the dielectric constant was used to investigate the band gap. Then, the Helpin-Tsai model was employed to predict Young’s moduli of the prepared nanocomposite films. On 3 wt.% ZnO nanofiller loading, the optical band gap of the PVA-based nanocomposite film was decreased from 5.26 eV to 3 eV, the tensile strength increased from 25.3 MPa to 48 MPa and Young’s modulus increased from 144 MPa to 544 MPa.

ZnO-CuO Nanocomposites with Improved Photocatalytic Activity for Environmental and Energy Applications

Abstract: A hydrothermal technique has been applied to synthesize ZnO–CuO nanocomposites that show very high photocatalytic efficiency under specific conditions. The structural, optical, and molecular vibrational properties of the nanocomposite samples were characterized by x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), photoluminescence, ultraviolet–visible (UV–Vis) spectroscopy, and Raman spectroscopy. High-resolution SEM and Rietveld analysis of the XRD data confirm the nanocomposite structure of ZnO–CuO with different ratios of ZnO and CuO phase contents. Raman spectra of the nanocomposites consist of optical vibrational modes of both ZnO and CuO. The unique photoluminescence spectra exhibited characteristic peaks in the visible range, confirming enhanced absorbance in the visible region of the solar spectrum. The photocatalytic activity of the synthesized samples was studied using degradation of methylene blue dye under UV–Vis illumination, revealing photocatalytic efficiency of 56% for the best nanocomposite sample. We also have studied the growth mechanism of the nanocomposite samples, the role of the nanocomposite as a photocatalytic material for wastewater decontamination based on its unique band structure, and the efficiency of the nanocomposite catalysts under different conditions.