Journal of Materials Science: Materials in Electronics

In this paper, the photoresponse properties are investigated for the pentacene thin film transistor with solution-processed silicon dioxide/graphene oxide (GO) bilayer insulators. The GO is synthesized by a modified Hummers method. It is determined that the electrical characteristics and photosensing parameters of the thin film transistor under dark and white light illuminations. The mobility µ value (3.752 × 10−1 cm2/Vs) of the thin film transistor under dark is lower than that of the value (4.557 × 10−1 cm2/Vs) under 100 mW/cm2 illumination. The interface trap density of the transistor is reduced with the rise various illuminations. The photoresponse of the thin film transistor with dioxide/GO bilayer insulators in the on state is lower than that of the thin film transistor in the off state. The photoresponse characteristics indicate that the pentacene thin film transistor with solution-processed silicon dioxide/GO bilayer insulators exhibits a phototransistor characteristic.

Hierarchically uniform three-dimensional europium-based metal–organic frameworks (Eu-MOFs) have been successfully fabricated via a facile and mild liquid precipitation method at room temperature. The morphology, structure, and composition of samples are well characterized by scanning electron microscopy, X-ray powder diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analyses, respectively. These well-arranged Eu-MOFs architectures show red emission corresponding to the 5D0/7F2 transition of the Eu3+ ions under UV light excitation. Remarkably, these Eu-MOFs samples exhibit clear “turn-off” quenching response for styrene vapors with high selectivity and reusability. This Eu-MOFs fluorescent sensor realizes fast recognition for styrene with a response time of less than 1 min at room temperature. Moreover, good detection reproductivity could also be achieved in this sensor. Considering the easy preparation, high selectivity and excellent repeatability, the sensor system provides a convenient and reliable detection of volatile organic compound in everyday applications.

In this work, we study the Transient Liquid Phase Bonding (TLPB) for flip chip interconnexion using copper pillar and SnAg solder alloy technologies. Cu and SnAg bumps with a size of 90 × 90 µm2 were deposited using electroplating process with a thickness of 20 µm and 15–30 µm, respectively. Two types of Cu were deposited: with or without additives. Before the TLPB process, soldering experiments with or without pre-reflow were carried out at 250 °C in order to insure a good filling of the joint. Afterwards, isothermal holdings up to 4 h were performed in the temperature range between 250 and 350 °C under air atmosphere. Two main aspects of Cu/SnAg system are studied and analyzed: (i) the evolution of morphology, microstructure, and growth kinetics of intermetallics (IMCs) during the TLPB and especially (ii) the formation and growth of gas bubbles within the liquid solder during TLPB process. Destructive (scanning electron microscopy) and non-destructive (X-ray) characterizations are performed to analyze and understand the evolution of microstructure as well as the formation and evolution of cavities within the joint during the TLPB process. Non-destructive X-ray radiography with 5 µm resolution and 3D X-ray tomography analysis with 0.7 µm resolution were conducted for the same joint at different steps of its evolution between its initial state (just after the soldering process: about 3 min at 250 °C) and 4 h at 250 °C in order to follow “in situ” the evolution of volume defects inside the joint and especially the evolution of gas bubbles within the joints.

Here we employed a facile low temperature molten-salt combustion method combined with two-stage calcination process to synthesize a series of Ni-doped spinel LiNi0.1Mn1.9O4 cathode materials. All the LiNi0.1Mn1.9O4 materials present well-defined cubic spinel structure with a representative Fd3m space group. With the elevated calcination temperature, the particle size and crystallinity increase simultaneously. Benefiting from the optimization of calcination temperature, the LiNi0.1Mn1.9O4 prepared at 600 °C reveals a favorable crystal structure and morphology consisted of homogeneous nanoparticles with a size of 90–110 nm. Consequently, the optimized LiNi0.1Mn1.9O4 cathode exhibits high rate capability and ultralong cycling stability with a discharge specific capacity of 97.1 mAh g−1 and a capacity retention of 63.5% after 1000 cycles at a high current rate of 10 and 25 °C. Even at a high-temperature of 55 °C, a high initial discharge capacity of 106.1 mAh g−1 and a good capacity retention of 79.0% is also obtained after 100 cycles at 5 C. Such an excellent electrochemical performance together with the facile synthesis approach may endow the as-prepared LiNi0.1Mn1.9O4 to be a promising practical application for high-power lithium-ion batteries.

NiFe2O4 nanostructures were synthesized via a facile precipitation method using green capping agents such as starch, glucose, gelatin, salicylic acid and polyvinylpyrrolidone in the water. Then nickel oxide and NiFe2O4–NiO (50:50%) nanocomposites were obtained by a simple chemical precipitation. The influence of concentration, surfactant, precipitating agent on the particle size and shape of the products were examined. The prepared samples were characterized by X-ray diffraction pattern, scanning electron microscopy, and Fourier transform infrared spectroscopy. Vibrating sample magnetometer shows the ferromagnetic property of the ferrite nanostructures. The photocatalytic behaviour of nickel oxide was evaluated using the degradation of three azo dyes (acid blue, acid violet and acid black) under ultraviolet and visible light irradiation. Our results confirm preparation of applicable nanocomposite with appropriate magnetic and photocatalytic performance. Interestingly outcomes show that photocatalysts can photo-degrade toxic dyes in <10 min.

Diazoaminobenzene shows semiconducting properties and a phenomenon of phase transition. The semiconducting properties arise as a result of high molecular resonance induced by intramolecular hydrogen bonding at the cliazo linkage. The phase transition is probably a consequence of thermal rotation into resolved cis and trans configurations; the frans form conducts electricity with a lower activation energy assisted by the molecular resonance. Thermal rotation into the more thermally stable cis form reduces the molecular resonance so that the resultant form conducts electricity with a higher activation energy. Unexpectedly, chelation with the favoured d-block element, Cu, reduces the electrical conductivity which is evidenced by a reduced electric dipole moment. Chelation appears to proceed favourably at the cis form, since the resultant complex conducts electricity with a similar high activation energy, a result of prohibited proton exchange. Restricted rotation in the Cu chelate explains conduction via a single phase. Consistent data from 1H-NMR, i.r. and u.v.—visible spectra do confirm the proposed structural interpretation.

Three-phase polymer electrolyte nanocomposite composed of polyvinyl-alcohol (PVA), manganese(II) chloride (MnCl2), and multiwall carbon nanotubes (MWCNTs) were prepared using the cast techniques. Impedance spectroscopy was used to investigate the AC electrical conductivity (σac) of two- and three-phase samples with different weight ratios of multiwall carbon nanotubes (MWCNTs) over a wide frequency range and at various fixed temperatures (30 °C to 120 °C). The frequency-dependent nature of σac was seen to follow Jonscher’s power law. The redistribution of accumulated charges was used to explain the change in the pre-exponent (n) and the constant (A) after the percolation threshold. As the temperature approached the glass transition temperature, the mobility of ions and polymeric chains also played an important role in this change. The Correlated Barrier Hopping (CBH) model was considered as the most predicted model for the samples at temperatures below 100 °C. However, the Quantum Mechanical Tunneling (QMT) model was predicted to be the most prevalent conduction model for temperatures greater than 100 °C. The values of the activation energy calculated from both Z” and M” are mostly close. Equivalent circuits were used to analyze the impedance spectra of the two- and three-phase samples. An attempt was made to explain the impedance behavior of the samples through the elements participating in the equivalent circuits.