[en] Structural properties of Cr₇₂Fe₁₈Mn₁₀ alloys prepared by mechanical alloying were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and ⁵⁷Fe Moessbauer spectroscopy. Lamellar structure with some small particles embedded in them was observed during the first stage of mechanical alloying. XRD results show that the α-Mn phase disappears with the milling time increasing up to 5 h. The as-milled samples maintain the BCC structure throughout the course of milling. For 30 h the paramagnetic Cr-Fe-Mn ternary alloys are obtained, the average crystalline size is about 42 nm considering the internal strains

[en] Langmuir probe is an important tool to diagnose the plasma in radio frequency (rf) glow discharge. A new method has been used to obtain the electron energy distribution function in plasma by the numerical differentiation of the I-V probe characteristic. This method is based on Fourier transform and could overcome the defects of other methods. In this way, the second derivative signal of Langmuir probe I-V characteristic is obtained automatically and accurately. The mean electron energy and electron concentrations in rf glow discharge plasma in silane were obtained by Langmuir probe

[en] Highlights: • First study on Cu(Cr_1_−_xMn_x)O_2 DMS thin films prepared by pulsed laser deposition. • Thin films show relatively balanced electrical, optical and magnetic properties. • p-Type conductivity is ∼3 orders of magnitude higher than literature values. • All thin films exhibit a comparatively high transparency in the visible range. • Ferromagnetism comes from the Mn"3"+–O–Mn"4"+ and Mn"3"+–O–Cr"3"+ double-exchanges. - Abstract: Cu(Cr_1_−_xMn_x)O_2 delafossite thin films (0 ⩽ x ⩽ 15 at.%), with a c-axis quasi-epitaxial orientation, were prepared by pulsed laser deposition. The effects of Mn content on microstructure and physical properties were investigated. Both the variation of lattice constant c and X-ray photoelectron spectroscopy reveal that the Mn ions substitute for Cr"3"+ as Mn"3"+ and Mn"4"+. The proportion of Mn"4"+ is gradually increased with the Mn doping, leading to the changes of hole density and mobility. As a result, the p-type conductivity is decreased at first and then increased. The conduction mechanism is thermal activation between 130 and 300 K. It is indicated that the PLD method and the Mn"3"+–O–Mn"4"+ and Mn"3"+–O–Cr"3"+ double-exchange interactions are favorable to the high hole density and mobility, respectively. Meanwhile, the double-exchange interactions produce the near-room-temperature ferromagnetism. The saturation magnetization and Curie temperature are gradually increased with the Mn content. For optical properties, all thin films have a comparatively high transmittance for visible light, with the highest value 70% for x = 15 at.% at the wavelength of 750 nm. As increasing the Mn content, the transparency and direct optical bandgap exhibit the similar trend as the hole density. With the relatively balanced electrical, magnetic and optical properties, these pulsed-laser-deposition-grown Cu(Cr_1_−_xMn_x)O_2 thin films are expected to become a promising p-type transparent diluted magnetic semiconductor material

[en] Graphical abstract: - Highlights: • ZnO nanorods synthesized on CVD-graphene and rGO surfaces, respectively. • ZnO/CVD-graphene and ZnO/rGO form a distinctive porous 3D structure. • rGO/ZnO nanostructures possibility in energy storage devices. - Abstract: In this work, reduced graphene oxide (rGO)/ZnO nanorods composites were synthesized on graphene coated PET flexible substrates. Both chemical vapor deposition (CVD) graphene and reduced graphene oxide (rGO) films were prepared following by hydrothermal growth of vertical aligned ZnO nanorods. Reduced graphene sheets were then spun coated on the ZnO materials to form a three dimensional (3D) porous nanostructure. The morphologies of the ZnO/CVD graphene and ZnO/rGO were investigated by SEM, which shows that the ZnO nanorods grown on rGO are larger in diameters and have lower density compared with those grown on CVD graphene substrate. As a result of fact, the rough surface of nano-scale ZnO on rGO film allows rGO droplets to seep into the large voids of ZnO nanorods, then to form the rGO/ZnO hierarchical structure. By comparison of the different results, we conclude that rGO/ZnO 3D nanostructure is more desirable for the application of energy storage devices

[en] Highlights: •First study on high-quality Cu(Cr_1−xFe_x)O₂ diluted magnetic semiconductor films. •All thin films have a quasi-epitaxial growth orientation along the c axis. •Room-temperature ferromagnetism comes from hole-mediated Fe³⁺–Cr³⁺ super-exchange. •P-type conductivity is enhanced by more than one order of magnitude via Fe doping. •All thin films show a comparatively high transparency in the visible range. -- Abstract: Fe-doped CuCrO₂ delafossite thin films, with a c-axis quasi-epitaxial orientation, were prepared by pulsed laser deposition, exhibiting reasonably good p-type conductivity, ferromagnetism with T_C well above room temperature, and comparatively high transparency in the visible range. The influence of Fe concentration (0–15 at%) on microstructure and physical properties was investigated. The substitution of Fe³⁺ for Cr³⁺ induces the lattice expansion, which is favorable for the oxygen insertion and thus produces the higher hole concentration. Accordingly the p-type conductivity is remarkably improved to 28 S cm⁻¹. Moreover, the introduction of Fe³⁺ leads to the hole-mediated Fe³⁺–Cr³⁺ super-exchange coupling responsible for the room-temperature ferromagnetism. The saturation magnetization is enhanced as the Fe concentration increases, with Curie temperature ⩾550 K. Nevertheless, the transparency in the visible range does not profit from the Fe doping. The transmittance is diminished from 75% for x = 0 to 65% for x = 15 at% at the wavelength of 750 nm, which can be interpreted as the strengthened scattering of photons by charge carriers. The direct optical bandgap is modulated by 3.8% via the Fe addition. The results show that the substitution of iron for chromium is an effective way to achieve high-performance CuCrO₂ thin films which are supposed to become a promising p-type transparent diluted magnetic semiconductor material

[en] Graphical abstract: -- Highlights: •The first study on the Fe content dependence of ferromagnetism in Cu(Cr_1−xFe_x)O₂. •Fe is confirmed to replace Cr³⁺ as Fe³⁺ by XRD, XPS and Mössbauer spectroscopy. •Hole-mediated Fe³⁺–Cr³⁺ super-exchange mechanism produces ferromagnetic behavior. •Curie temperature can be greatly enhanced close to room temperature by Fe doping. •Fe doping is an effective way for the dilute magnetism of CuCrO₂ delafossite. -- Abstract: The preferred c-oriented Cu(Cr_1−xFe_x)O₂ ceramics (0 ⩽ x ⩽ 15 at.%) were prepared by solid-state reaction. The effects of Fe concentration on microstructure, morphology and magnetism were investigated. All the samples have a pure 3R-CuCrO₂ delafossite structure, with a stress-induced preferential orientation. The lattice expansion supports the Fe entrance into the Cr sublattice in the form of Fe³⁺, which is further certified by the X-ray photoelectron spectra and the Mössbauer spectra. The Mössbauer study also reveals a preferential growth orientation and an increase of Fe–O bond lengths with the Fe addition, matching well with the X-ray diffraction analysis. Ferromagnetism is achieved in the Fe-doped samples with Curie temperatures higher than 246 K, which is expected to originate from the hole-mediated Fe³⁺–Cr³⁺ super-exchange interaction. The saturation magnetization of this CuMO₂ delafossite (M = Cr, Fe) is decreased almost linearly with the increasing Fe concentration, due to the combined influence of the number of the M–M pairs, the M–M distances and the hole concentration. The present work indicates that Fe-doped CuCrO₂ is a dilute magnetic semiconductor and Curie temperature can be remarkably enhanced to close to room temperature by Fe doping

[en] Zinc oxide/indium/zinc oxide multilayer structures have been obtained on glass substrates by magnetron sputtering. The effects of indium thickness on optical and electrical properties of the multilayer structures are investigated. Compared to a single zinc oxide layer, the carrier concentration increases from 8 x 10¹⁸ cm^-3 to 1.8 x 10²⁰ cm^-3 and Hall mobility decreases from 10 cm²/v s to 2 cm²/v s for the multilayer structure at 8 nm of indium thickness. With the increase of indium thickness, the transmittance decreases and optical band gap shifts to lower energy in multilayer structures. Results are understood based on Schottky theory, interface scattering mechanism and the absorption of indium layer.

[en] Highlights: • We developed a paper-based SERS substrate by gravure and inkjet printing methods. • The S-RGO/AgNPs comoposite structure had higher SERS activity than the pure AgNPs. • The Raman enhancement factor of S-RGO/AgNPs substrate was calculated to be 10"9. • The paper-based substrate exhibited good reproducibility and long-term stability. - Abstract: Paper-based surface-enhanced Raman scattering (SERS) substrates receive a great deal of attention due to low cost and high flexibility. Herein, we developed an efficient SERS substrate by gravure printing of sulfonated reduced graphene-oxide (S-RGO) thin film and inkjet printing of silver nanoparticles (AgNPs) on weighing paper successively. Malachite green (MG) and rhodamine 6G (R6G) were chosen as probe molecules to evaluate the enhanced performance of the fabricated SERS-active substrates. It was found that the S-RGO/AgNPs composite structure possessed higher enhancement ability than the pure AgNPs. The Raman enhancement factor of S-RGO/AgNPs was calculated to be as large as 10"9. The minimum detection limit for MG and R6G was down to 10"−"7 M with good linear responses (R"2 = 0.9996, 0.9983) range from 10"−"4 M to 10"−"7 M. In addition, the S-RGO/AgNPs exhibited good uniformity with a relative standard deviation (RSD) of 7.90% measured by 572 points, excellent reproducibility with RSD smaller than 3.36%, and long-term stability with RSD less than 7.19%.

[en] In the present work, (1-x)(0.935Bi_0.5Na_0.5TiO₃-0.065BaTiO₃)-xKNbO₃ (BNT-BT-KN, BNT-BT-100xKN) ceramics with x ranging from 0 to 0.1 were prepared by the conventional ceramic fabrication process. A large electrostrictive coefficient of ∝10^-2 m⁴ C^-2 is obtained with the composition x ranging from 0.02 to 0.1, which is close to the well-known electrostrictive material Pb(Mg_1/3Nb_2/3)O₃. Under an electric field of 4 kV/mm, the electrostrictive strain can reach as high as 0.08%. Besides, the electric field induced strain behavior indicates a temperature independent behavior within the temperature range of 20 to 150 C. The large electrostrictive strain is suggested to be ascribed to the formation of non-polar (NP) phase developed by the KNbO₃ substitution, and the high electrostrictive coefficient of BNT-BT-KN ceramics makes them great candidates to be applied in the new solid-state actuators. (orig.)

[en] The lateral geometry 4H-SiC photoconductive semiconductor switches (PCSS) were fabricated on the vanadium compensated semi-insulating 4H-SiC substrate with the Si (0001) Ni/Au contacts deposited by magnetron sputtering. The effect of laser excitation energy on the photoelectric response and that on the state resistance of PCSS were investigated. The experimental results showed that a nano-second pulse electric signal was obtained when the PCSS was triggered with a 532 nm wavelength laser light. The on state resistance decreased from 295 Ω to 197 Ω when the laser excitation energy increased from 26.7 mJ to 43.9 mJ. Based on the combination theory, the relationship between the carrier concentration and time deduced when the PCSS was irradiated. The on state resistance simulated from the MATLAB is consistent with the experimental results. Finally, the two ways to reduce the on resistance of the switch are put forward. (authors)