Promising Candidate For Electronic Applications Research Articles

Dielectric properties of nanocrystalline CaCu3Ti4O12 (CCTO) ceramics fabricated from Algerian limestone raw material

Algerian natural limestone was used to fabricate the perovskite CaCu3Ti4O12 phase (CCTO) to replace commercial calcium carbonate (CaCO3) powder by a solid-state method. X-ray diffraction analysis of CCTO ceramics sintered at 1010 °C manifested the formation of well-crystallized pure (CCTO) phase with narrow crystallite size (43–99 nm) without any additional phases after sintering beyond 4 h. Thermal analysis by DSC indicated that CCTO phase is stable up to 1151 °C, afterwards it decomposes into CaTiO3 and TiO2 and accompanied by the segregation of the CuO/Cu2O phase. Scanning electron microscopy observations of the ceramics sintered at 1010 °C showed that most of the grains have an average particle size in the narrow range of 1–2 μm. The sintered pellet at 1010 C° for 14 h showed the optimum density (>94%). This study highlights the importance of using natural calcium carbonates (extracted from Guelma limestone in Algeria) as potential replacement to commercial counterpart for the fabrication of dense well-crystallized perovskite-type ceramics with controlled particle size distribution as promising candidates for electronic applications.

Stereolithography of Semiconductor Silver and Acrylic-Based Nanocomposites.

Polymer nanocomposites (PNCs) attract the attention of researchers and industry because of their potential properties in widespread fields. Specifically, electrically conductive and semiconductor PNCs are gaining interest as promising materials for biomedical, optoelectronic and sensing applications, among others. Here, metallic nanoparticles (NPs) are extensively used as nanoadditives to increase the electrical conductivity of mere acrylic resin. As the in situ formation of metallic NPs within the acrylic matrix is hindered by the solubility of the NP precursors, we propose a method to increase the density of Ag NPs by using different intermediate solvents, allowing preparation of Ag/acrylic resin nanocomposites with improved electrical behaviour. We fabricated 3D structures using stereolithography (SLA) by dissolving different quantities of metal precursor (AgClO4) in methanol and in N,N-dimethylformamide (DMF) and adding these solutions to the acrylic resin. The high density of Ag NPs obtained notably increases the electrical conductivity of the nanocomposites, reaching the semiconductor regime. We analysed the effect of the auxiliary solvents during the printing process and the implications on the mechanical properties and the degree of cure of the fabricated nanocomposites. The good quality of the materials prepared by this method turn these nanocomposites into promising candidates for electronic applications.

Copolymers of 4‐thieno[3,2‐b]thiophen‐3‐ylbenzonitrile with anthracene and biphenyl; synthesis, characterization, electronic, optical, and thermal properties

AbstractTwo novel copolymers of 4‐thieno[3,2‐b]thiophen‐3‐ylbenzonitrile (TT‐CN), possessing electron withdrawing cyano moiety, with anthracene (P1) and biphenyl (P2) were prepared via Suzuki coupling. Optic, electronic, and thermal properties of the copolymers were investigated through UV–Vis spectroscopy, cyclic voltammetry, gel permeation chromatography, and thermal gravimetric analysis. The polymers with anthracene and biphenyl had electronic band gaps of 2.01 and 1.90 eV, respectively. Both polymers demonstrated excellent large Stokes shifts of 101 (anthracene) and 105 nm (biphenyl) as well as very good thermal properties. As they had good optical, electronic, and thermal properties, they are promising candidates for electronic applications.

Resistive Switching Memory Performance of Two-Dimensional Polyimide Covalent Organic Framework Films.

Two-dimensional polyimide covalent organic framework (2D PI-NT COF) films were constructed on indium tin oxide-coated glass substrates to fabricate two-terminal sandwiched resistive memory devices. The 2D PI-NT COF films condensated from the reaction between 4,4',4″-triaminotriphenylamine and naphthalene-1,4,5,8-tetracarboxylic dianhydride under solvothermal conditions demonstrated high crystallinity, good orientation preference, tunable thickness, and low surface roughness. The well-aligned electron-donor (triphenylamine unit) and -acceptor (naphthalene diimide unit) arrays rendered the 2D PI-NT COF films a promising candidate for electronic applications. The memory devices based on 2D PI-NT COF films exhibited a typical write-once-read-many-time resistive switching behavior under an operating voltage of +2.30 V on the positive scan and -2.64 V on the negative scan. A high ON/OFF current ratio (>106 for the positive scan and 104-106 for the negative scan) and long-term retention time indicated the high fidelity, low error, and high stability of the resistive memory devices. The memory behavior was attributed to an electric field-induced intramolecular charge transfer in an ordered donor-acceptor system, which provided the effective charge-transfer channels for injected charge carriers. This work represents the first example that explores the resistive memory properties of 2D PI-COF films, shedding light on the potential application of 2D COFs as information storage media.

Effect of Zn substitution on temperature dependent magnetic properties of BaFe12O19 hexaferrites

Zinc doped barium hexaferrite powders with chemical composition BaFe12-xZnxO19 (0.0 ≤ x ≤ 0.3) were synthesized by sol-gel auto combustion method. The effect of zinc ion concentration on the temperature-dependent magnetic properties of BaFe12-xZnxO19 hexaferrites has been comprehensively investigated in the temperature range of 10–300 K and magnetic field of ±50 kOe. XRD powder patterns showed a pure single phase structure. The Rietveld refinement of the XRD patterns revealed the existence of hexagonal structure with P63/mmc space group. The average crystallite size of the powders was found to be in the range of 46–51 nm. The ratio of lattice constants (c/a) lower than 3.98 proves that BaFe12-xZnxO19 hexaferrite powders have a M-type hexagonal ferrite structure. The nonmagnetic zinc ions strongly affect the magnetic properties of the powders. The magnetic hysteresis loops were fitted by using a ‘law of approach to saturation’. From the linear fitting, the magnetic parameters were calculated such as saturation magnetization, effective magnetic anisotropy and anisotropy field. The saturation magnetization values close to bulk values were determined as 66.67 and 95.47 emu/g for 300 and 10 K, respectively, which makes the samples a promising candidate for electronic applications. The saturation magnetization slowly decreases and then increases, whereas the coercive field continuously decreases with the increasing of Zn2+ concentration (x). The squareness ratio (Mr/Ms) of about 0.5 confirmed that the hexaferrite powders have a uniaxial anisotropy. The effective magnetic anisotropy constant (Keff) was observed to decrease with the increase in Zn2+concentration. When the temperature increases, the saturation magnetization continuously decreases because of the weakening of superexchange interaction and the coercive field increases due to the increasing of anisotropy field. FMR measurements confirmed the ferromagnetic behaviour of the substituted barium hexaferrite powders. The high resonance field values of the powders (a maximum resonance field of 16 kOe) originate from the hard magnetic property of the hexaferrites used in this study. The absorption curves have a broad FMR linewidth due to an anisotropy axis randomly distributed and the competing between anisotropy and exchange fields.

Inverted OPVs with MoS2 hole transport layer deposited by spray coating

Molybdenum disulphide (MoS2) exhibits high work function and high mobility, making it a promising candidate for electronic applications. Currently, most applications require high vacuum or high reaction temperature processes to deposit MoS2. Here, we report organic photovoltaic devices made by room-temperature spray-coating of liquid-exfoliated MoS2 suspension to form hole transport layer (HTL) on top of poly(3-hexylthiophene):phenyl-C60-butyric acid methyl ester bulk heterojunction. Such an approach is compatible with large area applications. Current-voltage data showed that fill factor of devices with MoS2 HTL is similar to the devices using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) HTL. However, open circuit voltage and short circuit current density (Jsc) are reduced, with the amount of Jsc reduction depending strongly on active layer thickness. These results can be understood by the strong absorption of light by MoS2, reducing/eliminating the back reflection from the top silver electrode. The experimental results are corroborated by calculations using transfer matrix method.