Controlling magnetic-semiconductor properties of the Si- and Al-doped blue phosphorene monolayer

Doping has been widely employed as an efficient method to diversify the materials properties. In this work, the structural, magnetic, and electronic properties of pristine, aluminum(Al)-, and silicon(Si)-doped blue phosphorene monolayer are investigated using first-principles calculations. Pristine monolayer is a non-magnetic wide gap semiconductor with a band gap of 1.81 eV. The 1Si-doped system is a ferromagnetic semiconductor. However, the magnetism is turned off when increasing the dopant composition with small Si-Si distance. Further separating the dopants recovers step by step the magnetic properties, and an antiferromagnetic(AFM)-ferromagnetic(FM) state transition will take place at large dopants separation. In contrast, Al doping retains the non-magnetic semiconductor behavior of blue phosphorene. However, significant energy gap reduction is achieved, where this parameter exhibits a strong dependence on the dopant concentration and doping configuration. Such control may also induce the indirect-direct gap transition. Our results introduce prospective two-dimensional (2D) materials for applications in spintronic and optoelectronic nano devices, which can be realized and stabilized in experiments as suggested by the calculated formation and cohesive energies.

Термоэлектрические и мемристивные особенности структур Sb-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=-/Sb-=SUB=-2-=/SUB=-S-=SUB=-3-=/SUB=-/Sb-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=- и Ag/Sb-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=-/Ag

Single-layer Sb2Te3 films and three-layer Sb2Te3/Sb2S3/Sb2Te3 structures are obtained by thermal vacuum deposition. Their thermoelectric characteristics have been investigated in a wide temperature range (5350 K). It is shown that the conductivity of Sb2Te3/Sb2S3/Sb2Te3 has a semiconductor behavior, the resistivity is an order of magnitude higher than the resistivity of the Sb2Te3 film; the Seebeck coefficient of Sb2Te3/Sb2S3/Sb2Te3 is 1.5 and 3 times higher than the Seebeck coefficient of the film and single-crystal Sb2Te3, respectively. The currentvoltage characteristics of the Sb2Te3 film exhibit memristive properties with unipolar resistive switching, whereas Sb2Te3/Sb2S3/Sb2Te3 can be considered as a memristor with a parallel connected capacitance.

Superconductivity of BSCCO Compound Substituted Partially by Zr Nanoparticles at Bi Site

High-temperature superconductors with a nominal composition Bi2- xZrxPb0.4Sr2Ca2Cu3Oy for (0≤x≤0.3) were prepared by solid-state reaction method. Effects of the Zr nanoparticles substitution at Bi sites have been studied to obtain the optimum concentration for the formation and stabilization of the superconducting samples. Electrical resistivity measurements of the samples showed that the higher critical temperature TC was found at 118 K, which is for the composition Bi1.95Zr0.05Pb0.4Sr2Ca2Cu3Oy. Semiconductor behavior noticed for samples with concentration higher than 0.2. The X-ray diffraction results for all superconducting samples showed an orthorhombic structure with two phases, 2223 high-TC phase and 2212 low-TC phase. The scanning electron microscope has been used to identify the morphology of the superconducting phase. The plate-like grains of the high Bi-2223 phase appeared in most samples besides changes in morphology of the samples with increasing dopant concentration

Efficient Film Fabrication and Characterization of Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) (PEDOT:PSS)-Metalloporphine Nanocomposite and Its Application as Semiconductor Material

The use of composite films with semiconductor behavior is an alternative to enhance the efficiency of optoelectronic devices. Composite films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and metalloporphines (MPs; M = Co, Cu, Pd) have been prepared by spin-coating. The PEDOT:PSS-MP films were treated with isopropanol (IPA) vapor to modify the polymer structure from benzoid to quinoid. The quinoid structure promotes improvements in the optical and electrical behavior of films. The composite films’ morphology and structure were characterized using infrared and Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Composite films were analyzed for their optical behavior by ultraviolet-visible spectroscopy: at λ < 450 nm, the films become transparent, indicating the capacity to be used as transparent electrodes in optoelectronic devices. At λ ≥ 450 nm, the absorbance in the films increased significantly. The CoP showed an 8 times larger current density compared to the CuP. A light induced change in the J-V curves was observed, and it is larger for the CoP. The conductivity values yielded between 1.23 × 102 and 1.92 × 103 Scm−1 and were higher in forward bias.

Tuning the electronic and magnetic properties of defect blue phosphorene by the adsorption of nonmetal atoms

Based on the first principles of density functional theory, the adsorption of nonmetallic atoms on the surface of defective blue phosphorene was investigated. The results show that the most stable sites of different nonmetallic atoms on the defect blue phosphorene are different. The nonmetal (B, C, N, O) atoms were adsorbed on SV and SW defects blue phosphorene respectively. It was observed that B, N adsorbed SV defect blue phosphorene systems exhibited semiconducting behavior, whereas O adsorbed SV defect blue phosphorene system exhibited metallic behavior, and C adsorbed SV defect blue phosphorene system exhibited magnetic semiconducting behavior. For SW defect blue phosphorene, the results show that B, N, adsorbed SW defect blue phosphorene showed magnetic semiconductor behavior, while C, O adsorbed SW defect blue phosphorene showed semiconductor behavior.

Deposition and Characterization of Innovative Bulk Heterojunction Films Based on CuBi2O4 Nanoparticles and Poly(3,4 ethylene dioxythiophene):Poly(4-styrene sulfonate) Matrix

This work presents the deposition and study of the semiconductor behavior of CuBi2O4 nanoparticles (NPs) with an average crystallite size of 24 ± 2 nm embedded in poly(3,4 ethylene dioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) films. The CuBi2O4 NP bandgap was estimated at 1.7 eV, while for the composite film, it was estimated at 2.1 eV, due to PEDOT:PSS and the heterojunction between the polymer and the NPs. The charge transport of the glass/ITO/PEDOT:PSS-CuBi2O4 NP/Ag system was studied under light and dark conditions by means of current–voltage (I–V) characteristic curves. In natural-light conditions, the CuBi2O4 NPs presented electric behavior characterized by three different mechanisms: at low voltages, the behavior follows Ohm’s law; when the voltage increases, charge transport occurs by diffusion between the NP–polymer interfaces; and at higher voltages, it occurs due to the current being dominated by the saturation region. Due to their crystalline structure, their low bandgap in films and the feasibility of integrating them as components in composite films with PEDOT:PSS, CuBi2O4 NPs can be used as parts in optoelectronic devices.

AgSn[Bi1−xSbx]Se3: Synthesis, Structural Characterization, and Electrical Behavior

Herein, we report the synthesis, characterization, and electrical properties of lead-free AgSnm[Bi1−xSbx]Se2+m (m = 1, 2) selenides. Powder X-ray diffraction patterns and Rietveld refinement data revealed that these selenides consisted of phases related to NaCl-type crystal structure. The microstructures and morphologies of the selenides were investigated by backscattered scanning electron microscopy, energy-dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. The studied AgSnm[Bi1−xSbx]Se2+m systems exhibited typical p-type semiconductor behavior with a carrier concentration of approximately ~+1020 cm−3. The electrical conductivity of AgSnm[Bi1−xSbx]Se2+m decreased from ~3.0 to ~10−3 S·cm−1 at room temperature (RT) with an increase in m from 1 to 2, and the Seebeck coefficient increased almost linearly with increasing temperature. Furthermore, the Seebeck coefficient of AgSn[Bi1−xSbx]Se3 increased from ~+36 to +50 μV·K−1 with increasing Sb content (x) at RT, while its average value determined for AgSn2[Bi1−xSbx]Se4 was approximately ~+4.5 μV·K−1.

Theoretical investigation of ternary semiconductors half-Heusler RhTaZ (Z = Si, Ge and Sn) for thermoelectric applications

The structural, electronic, elastic, thermodynamic and thermoelectric properties of RhTaZ (Z = Si, Ge and Sn) half-Heusler materials have been studied using density functional theory. We have found that the compounds studied can be experimentally synthesized. Also, RhTaZ (Z = Si, Ge and Sn) alloys exhibit a semiconductor behavior following the Slater–Pauling rule. The elastic properties calculated confirm that our compounds are mechanically stable. Using Debye’s quasi-harmonic model, the thermodynamic properties of these half-Heusler alloys were investigated. For the study of thermoelectric properties, the semi-classical Boltzmann theory, as implemented in the BoltzTraP code, has been used. The high values obtained from the figure of merit for RhTaZ (Z = Si, Ge and Sn) compounds suggest that they are promising candidates for thermoelectric applications at low and high temperatures.

Graphene Oxide Layer-by-Layer Films for Sensors and Devices

Layer-by-layer films of poly (allylamine hydrochloride) (PAH) and graphene oxide (GO) were characterized, looking at growth with the number of bilayers, morphology, and electrical properties. The PAH/GO films revealed a linear increase in absorbance with the increase in the number of deposited bilayers, allowing the determination that 10.7 ± 0.1 mg m−2 of GO is adsorbed per unit of area of each bilayer. GO absorption bands at 146, 210, 247 and 299 nm, assigned to π-π* and n-π* transitions in the aromatic ring (phenol) and of the carboxylic group, respectively, were characterized by vacuum ultraviolet spectroscopy. The morphological characterization of these films demonstrated that they are not completely uniform, with a bilayer thickness of 10.5 ± 0.7 nm. This study also revealed that the films are composed of GO and/or PAH/GO fibers and that GO is completely adsorbed on top of PAH. The electrical properties of the films reveal that PAH/GO films present a semiconductor behavior. In addition, a slight decrease in conduction was observed when films were prepared in the presence of visible light, likely due to the presence of oxygen and moisture that contributes to the damage of GO molecules.