Journal of Materials Science: Materials in Electronics

Polyindole (PIn), combining the good properties of polypyrrole and poly(para-phenylene), has been gained significant attention. But the capacitive performances of PIn and its derivatives electropsynthesized in boron trifluoride diethyl etherate (BFEE) were unknown so far. So we first prepared the free-standing PIn film in BFEE and studied its capacitive property. The specific capacitance value of PIn could achieve 270.2 F g−1 at high current density of 10 A g−1. And the capacitance retained of PIn 84.06% after 3000 cycles. For further studying the effect of introducing alkyl chains on the electrochemical properties of PIn, poly1,3-di(1H-indol-1-yl)propane (P(IP-3)), poly1,6-di(1H-indol-1-yl)hexane (P(IH-6)), and poly1,12-di(1H-indol-1-yl)dodecane (P(ID-12)) bridged by alkyl chains with different lengths were electrosynthesized in BFEE. Through a series of experiments, we found that the specific capacitance performances of P(IP-3), P(IH-6), and P(ID-12) were poorer than PIn, indicating the introduction of alkyl chains altered the electrochemical properties of the π-conjugated backbone of PIn and lowered its the properties, which could be proved by scanning electron microscope.

With electronic devices progressing into more miniaturized and intelligent, thermal cycling reliability of solder joint has always been an issue in high-density advanced packaging. In this study, minor amount of graphene nanosheets (GNSs) was added into Sn-1.0Ag-0.5Cu solder in order to enhance its thermal cycling reliability. Detailed relationship between mechanical behavior and microstructure evolution of the Sn-1.0Ag-0.5Cu and Sn-1.0Ag-0.5Cu-GNSs solder joints was investigated. Experimental results indicated that Sn-1.0Ag-0.5Cu-GNSs had a lower decrease rate in shear force during thermal cycling when compared to the non-modified. This is due to a slower coarsening of microstructure and inhibited growth of interfacial IMCs. Theoretical analysis showed that with the addition of GNSs, the average growth coefficients of total interfacial IMCs (DT) was decreased from 8.6 × 10–11 to 6.7 × 10–11 cm2/h, respectively. This decrease in the average values of DT were mainly attributed to the pinning effect of GNSs on the the interfacial IMC growth during TC treatment. In addition, fracture mode of solder joints were also a good response to the mechanical change during thermal cycling treatment.

In the current study, the effect of vanadium particles on the electrical, superconducting, crystallographic, key structural and morphological features of Bi1.8Sr2.0Ca2.2Cu3.0VxOy superconducting materials is examined with the aid of powder X-ray diffraction (XRD), scanning electron microscope (SEM), electron-dispersive X-ray (EDX) and dc electrical resistivity over the temperature (ρ-T). The vanadium-added Bi1.8Sr2.0Ca2.2Cu3.0VxOy (Bi-2223) superconducting materials are prepared within the molar ratios between x = 0.00 and 0.30 using the conventional solid-state reaction technique. The temperature-dependent electrical resistivity measurements show that the existence of vanadium atom in the superconducting system damages seriously the Bi-2223 (high-Tc) phase content in the crystal structure as a result of the formations/disappearances of new impurity phases. On this basis, the amplitude Ψ0 of wave function founded on the super-electrons is considerably reduced with the vanadium addition. The critical onset and offset transition temperature values truncate from the values of 110.92 K and 97.45 K to 103.17 K and 18.38 K in case of the maximum vanadium addition level of x = 0.30. Similarly, the XRD results present that the average crystallite size and c-axis length parameters are noted to decrease considerably whereas a-axis length, strain and relativistic dislocation density ratios are calculated to enlarge harshly depending on the addition content level. It is also obtained that the vanadium inclusions lead to increase seriously the permanent crystal structure problems, disorders, misorientations, lattice strains, crack-producing omnipresent flaws and grain boundary coupling problems in the active Cu–O2 consecutively stacked layers in the superconducting core, being assured by SEM analyses. Besides, the SEM results show that the enhancement of vanadium addition level in the crystal structure damages remarkably the flaky layers of platelet-like shape for the grains. In fact, the excess vanadium addition seriously damages the general characteristic view (flaky layer structure) of Bi-2223 compound. Based on the EDX findings, the main reason for the degradation of fundamental characteristic properties of Bi-2223 system may stem from the possible replacement of aliovalent vanadium impurities for the copper-sites in the crystal structure. Namely, the vanadium addition in the crystal structure is ploughed to improve the fundamental crystallographic and electrical-superconducting features of bulk Bi-2223 superconducting materials.

We demonstrate enhanced hole injection into organic hole transport layers (HTL) from submonolayer NiOx, SnOx, and LiF nanoparticle hole injection layers (HIL) produced using reverse micelle templating. Decoration of ITO with nanoparticle HIL shifts the hole barrier height at the interface by modifying the electrical structure of the interfacial surface even though the submonolayers show different coverage rates with different sizes and spacing. The current density–voltage characteristics of hole-only devices using nanoparticles are higher than a non-decorated ITO anode, corresponding to the dynamic barrier height shift. Using reverse micelle templating allows the uncoupling of the effect of a non-uniform electric field from nanoscale objects from the impact of the material properties. Larger nanoparticles with greater coverage show less effective injection than smaller particles with low coverage. Using this assessment, a single monolayer of LiF with particles $$\sim$$ 6 nm, and 21.5% coverage shows the highest hole injection for a single layer of particles, but NiO as a material has greater capacity for hole injection per volume of material on the surface, as particles of $$\sim$$ 8 nm with only 5.6% coverage can still act to improve charge injection. As this optimal performance is highly dependent on the organic layer and the nature of the contact with respect to trap states, tuning the size and density of the nanoparticle arrays seems to be an effective route to optimizing HILs for novel organic materials in next generation devices.

A microwave irradiation-based high-efficiency method was utilized in this study to prepare novel chromium (III) oxide (Cr2O3) nanostructures with their own distinctive properties. The synthesis method was accordingly conducted in optimum conditions for the time duration of 20 min, the power of 360 W, and the microwave temperature of 30 °C. The scanning electron microscopy (SEM) micrographs also revealed a highly homogeneous morphology of crystalline nanostructures. Besides, the X-ray powder diffraction (XRD) and the differential scanning calorimetry (DSC) data demonstrated the single-phase existence of these components. Thermal stability and development of pure Cr2O3 samples were further investigated by thermo-gravimetric analysis (TGA) and DSC. Moreover, the Brunauer–Emmett–Teller (BET) technique showed a high specific surface area and significant porosity of these materials. As well, value-stream mapping (VSM) was employed to test the magnetic characteristics of the products. The findings established that microwave irradiation could play a key role in the synthesis of Cr2O3 compounds in environmental conditions. The effective microwave-assisted route applied in this study for the synthesis of Cr2O3 nanocatalysts with high physico-chemical properties was also remarkable compared with other nanocatalysts.

Cadmium lead-borate reinforced with Nd3+ ions glass systems in the composition (60 − x) B2O3+20CdO+20PbO+xNd2O3, where x = (0, 1, 2, 3, 4, and 5 wt%) were prepared using the melt and quench method. The fabricated glasses were coded as BCPNdx. The direct effect of Nd3+ ions on fabrication, physical, structure, and optical characteristics of the fabricated glasses has been investigated. XRD patterns confirmed that all fabricated glasses were in amorphous state. Density was increased from 5.034 g/cm3 for BCPNd0 (with free Nd3+ ions) to 5.282 g/cm3 for BCPNd5 (with 5 wt% of Nd2O3). Both indirect and direct optical band gaps (Eg) were found to increase from (1.52 to 2.57 eV) and (1.95 to 3.19 eV), respectively, with the increase in the content of Nd2O3. Urbach energy ( $${E}_{\mathrm{U}}$$ ) values of the synthesized glass samples decreased by the increase in Nd2O3 content and changed inversely with (Eg) of the samples. Values of the oscillator energy (Eo) of the fabricated glasses varied from 2.58 to 6.34 eV, while the dispersion energy (Ed) varied from 3.34 to 8.41 eV. Real part of dielectric values decreases with the increase in the wavelength up to 350 nm, and then stays almost constant, with minor differences between different samples. Both bulk energy loss and surface energy loss increase with the increase in Nd3+ content corresponding to an increase of the bulk and surface energy loss. The amorphous nature of the glasses can be identified from the broad peaks of FTIR absorbance spectra.

In this study, I investigated the effect of work function (ϕm) of AuxAg1−x (x = 0, 0.22, 0.37, 0.71 and 1) on the Au–Ag/n-GaAs Schottky diode (SD) parameters. Ag, Au metals and three alloys with different compositions deposited on n-GaAs substrates by the thermal evaporation method. Surface morphologies of the samples were investigated by an atomic force microscope (AFM). Elemental compositions of Schottky contact metals were conducted by energy dispersive X-ray spectroscopy (EDX). Current–voltage (I–V) and capacitance–voltage (C–V) measurements were performed at room temperature. SD parameters such as barrier height (Φb0), ideality factor (n), series resistance (Rs), and interface state density (Dit) of the SD’s were calculated from the obtained I–V and C–V data. Experimental results showed that all calculated SD parameters depend on the alloy composition. The lowest mean barrier height value was found as 0.789 ± 0.022 eV for Au/n-GaAs SDs and the highest value was determined 0.847 ± 0.008 eV for Au0.71Ag0.29/n-GaAs SDs from I–V measurements. Weak dependencies of barrier height to ϕm existed and gap state parameter (S) determined as 0.0526. The S value was close to the Bardeen limit (S = 0) and indicates that the Fermi level was strongly pinned in Au–Ag/n-GaAs SDs. Also, main SD parameters like series resistance (Rs), ideality factor (n), reverse bias barrier height (ΦbRB), doping density (Nd) and density of interface states (Dit) were calculated via using different methods from I–V and C–V measurement results. Also, to determine the leakage current mechanism Poole–Frenkel emission (PFE) and Schottky emission (SE) models applied on reverse bias I–V data.

Fused amorphous SiO2 filled polytetrafluoroethylene (PTFE) microwave substrate composites were manufactured. The composition of all the samples was 57 wt% SiO2 and 43 wt% PTFE. The effects of compound silane coupling agents on the properties of the SiO2 filled PTFE composites were investigated, including density, water absorption, dielectric properties and temperature coefficient of dielectric constant. Compound coupling agents x wt% KH550+ (1.5−x) wt% F8261 (x: mass ratio to SiO2 ceramic, x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were used to pre-treat SiO2 fillers and the performance of composites were improved with appropriate amounts of coupling agents. The SEM results show that SiO2 particles modified with compound coupling agents are well dispersed in PTFE polymer and exhibit a strong connection with PTFE. The dielectric constant of all the composites shows excellent frequency stability within the frequency from 1 to 18 GHz. The SiO2 ceramic filler modified with 1.1 wt% F8261 and 0.4 wt% KH550 simultaneously has the highest contact angle and the lowest surface energy, besides, the composite achieves a most compact structure with a maximum density of 2.059 g/cm3. At the same time, this composite obtains optimal properties, including good dielectric properties (ε r  ~ 2.89, tanδ ~ 0.0007), acceptable water absorption of 0.2%, temperature coefficient of dielectric constant (τ ε ) of 32.32 ppm/°C. Moreover, the ratio of experimental and theoretical dielectric constant can achieve 98.86%, which is far greater than that in previous reports.