The system consists of Co diluted in TiO2 nanotubes obtained by electrochemical anodization process over Co/Ti foils, with NH4F, distilled water, and ethylene glycol. Cobalt was deposited on the Ti foils (99.99% purity) via DC magnetron sputtering at room temperature. The anodization process establishes the percentage of Co dilution into the TiO2 matrix around 0.67 wt. % through EDXS measurements. The nanostructure of the nanotubes was evidenced by the SEM micrographs. These measurements permitted the observation of nanotubes with a hollow hexagonal morphology. Nevertheless, we model this nanotube as a cylindrical-hollow nanotube with inner and outer radii ∼15 and 30 nm, respectively, and the height is 96.6 nm according to the SEM micrographs. The I–V curves show a bipolar resistive behavior with the resistance ratio high resistance state/low resistance state remaining essentially stable, around 1.22. The results obtained through Ubermag environment simulations were compared with experimental magnetization measurements as a function of the magnetic field at room temperature for Co-doped TiO2 nanotubes. This comparison enabled their analysis as a diluted magnetic material for potential applications in information storage memories.

This work investigates the impact of Mn and Co doping on the structural, morphological, electrical, and magnetic properties of ZnO thin films deposited via DC magnetron co-sputtering. Doping concentration, substrate temperature, and substrate type (soda-lime glass and oriented silicon wafer) were systematically varied for potential spintronic applications. X-ray diffraction (XRD) and Raman spectroscopy confirmed the formation of a hexagonal wurtzite crystalline structure with a preferential [002] growth orientation when Mn was incorporated into the ZnO matrix. Raman analysis also ruled out the presence of secondary Co oxide phases in ZnO:Co samples. Films doped with Mn at 25 W exhibited compressive stress of -0.345 %, which increased to -2.03 % at 50 W, highlighting the dopant's impact on lattice strain. FTIR spectra revealed characteristic bands of ZnO:Co, indicating successful incorporation of Co ions into the matrix. SEM and magnetic force microscopy (MFM) showed granular surface morphology and cluster formation at higher Mn concentrations (50 W). Electrical measurements revealed unipolar and bipolar resistive switching (RS) behaviors, associated with the Schottky barrier model, and strongly influenced by substrate temperature and doping levels. Notably, samples doped with Co at 50 W exhibited enhanced interfacial RS properties. Vibrating sample magnetometry (VSM) demonstrated room-temperature ferromagnetic hysteresis in films synthesized at Ts = 423 K, with Mn (25 W) and Co (50 W) doping. These findings validate the potential of ZnO:Mn/Co as a dilute magnetic semiconductor (DMS) for spintronic applications, offering tailored magnetic and resistive properties through precise control of doping and synthesis parameters.

Degradation of pollutants in aqueous medium is of high interest due to the impact on environment and human health, therefore, design and study of the physico-chemical properties of photocatalysts for water remediation are of major significance. Among properties of photocatalyst, those related to the surface and electrical mechanism are crucial to the photocatalyst´s performance. Here we report the chemical and morphological characteristics of TiO 2 @zeolite photocatalyst by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) respectively, and a coherent electrical conduction mechanism was proposed based on data obtained from assisted laser impedance spectroscopy (ALIS), in which the zeolite was synthesized from recycled coal fly ash. The results obtained by SEM and XPS verified the presence of spherical particles of TiO 2 anatase with presence of Ti 3+ state. ALIS results showed that impedance of the entire system increases when the amount of TiO 2 increases and the samples with lower capacitive performance allowed a larger transfer of the charges between the solid–liquid interface. All results showed that higher photocatalytic performance of TiO 2 growth over hydroxysodalite with 8.7 wt% and 25 wt% of TiO 2 can be explained in terms of the morphology of TiO 2 and the interactions between substrate-TiO 2 mainly.

The functional derivative of the superconducting transition temperature Tc with respect to the electron-phonon coupling function [Formula: see text] permits identifying the frequency regions where phonons are most effective in raising Tc. This work presents an analysis of temperature effects on the calculation of the δTc/δα2F(ω) and μ* parameters. The results may permit establishing that the variation of the temperature in the δTc/δα2F(ω) and μ* parameter allows establishing patterns and conditions that are possibly related to the physical conditions in the superconducting state, with implications on the theoretical estimation of the Tc.

Abstract Photocatalytic reactions to degrade organic pollutants from aqueous medium by hybrid materials is a field of high interest in which the solving of the exact electrical conduction mechanism is a challenge. A coherent electrical conduction mechanism was proposed based on data obtained from assisted laser impedance spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy for TiO2@zeolite hybrid materials where the zeolite was synthesized from recycled coal fly ash. The results verified the presence of a Ti3+ state in spherical particles of TiO2, in which the electrical resistance of the entire system increases when the amount of TiO2 increases. The samples with lower capacitive performance allowed a larger transfer of the charges between the solid-liquid interface.

Cooper-pair distribution function, $$D_{cp}(\omega ,T_c)$$ , is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the $$N_{cp}$$ parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature $$T_c$$ . Herein, we reported $$D_{cp}(\omega ,T_c)$$ function of the compressed $$D_3S$$ and $$H_3S$$ high- $$T_c$$ conventional superconductors, including the effect of stable sulfur isotopes in $$H_3S$$ . $$D_{cp}(\omega ,T_c)$$ suggests that the vibration energy range of 10–70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron–phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in $$H_3S$$ by its stable isotopes can lead to important changes in $$T_c$$ . The results also show proportionality between $$N_{cp}$$ parameter and experimental or theoretical $$T_c$$ values.

Cooper-pair distribution function, D_cp(ω ,T_c) , is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the N_cp parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature T_c . Herein, we reported D_cp(ω ,T_c) function of the compressed D_3S and H_3S high- T_c conventional superconductors, including the effect of stable sulfur isotopes in H_3S . D_cp(ω ,T_c) suggests that the vibration energy range of 10–70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron–phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in H_3S by its stable isotopes can lead to important changes in T_c . The results also show proportionality between N_cp parameter and experimental or theoretical T_c values.

Cooper-pair distribution function, [Formula: see text], is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the [Formula: see text] parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature [Formula: see text]. Herein, we reported [Formula: see text] function of the compressed [Formula: see text] and [Formula: see text] high-[Formula: see text] conventional superconductors, including the effect of stable sulfur isotopes in [Formula: see text]. [Formula: see text] suggests that the vibration energy range of 10-70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron-phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in [Formula: see text] by its stable isotopes can lead to important changes in [Formula: see text]. The results also show proportionality between [Formula: see text] parameter and experimental or theoretical [Formula: see text] values.

Cooper-pair distribution function, $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) , is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the $$N_{cp}$$ N cp parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature $$T_c$$ T c . Herein, we reported $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) function of the compressed $$D_3S$$ D 3 S and $$H_3S$$ H 3 S high- $$T_c$$ T c conventional superconductors, including the effect of stable sulfur isotopes in $$H_3S$$ H 3 S . $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) suggests that the vibration energy range of 10–70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron–phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in $$H_3S$$ H 3 S by its stable isotopes can lead to important changes in $$T_c$$ T c . The results also show proportionality between $$N_{cp}$$ N cp parameter and experimental or theoretical $$T_c$$ T c values.

AbstractCooper-pair distribution function, $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) , is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the $$N_{cp}$$ N cp parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature $$T_c$$ T c . Herein, we reported $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) function of the compressed $$D_3S$$ D 3 S and $$H_3S$$ H 3 S high-$$T_c$$ T c conventional superconductors, including the effect of stable sulfur isotopes in $$H_3S$$ H 3 S . $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) suggests that the vibration energy range of 10–70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron–phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in $$H_3S$$ H 3 S by its stable isotopes can lead to important changes in $$T_c$$ T c . The results also show proportionality between $$N_{cp}$$ N cp parameter and experimental or theoretical $$T_c$$ T c values.

AbstractIn this paper, we report Cooper Pairs Distribution function $${D}_{cp}(\omega ,{T}_{c})$$ D cp ( ω , T c ) for bcc Niobium under pressure. This function reveals information about the superconductor state through the determination of the spectral regions for Cooper-pairs formation. $${D}_{cp}(\omega ,{T}_{c})$$ D cp ( ω , T c ) is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. $${D}_{cp}(\omega ,{T}_{c})$$ D cp ( ω , T c ) for Nb suggests that the low-frequency vibration region $$\left(\omega <6 \,{\text{meV}}\right)$$ ω < 6 meV is where Cooper-pairs are possible. From $${D}_{cp}(\omega ,{T}_{c})$$ D cp ( ω , T c ) , it is possible to obtain the $${N}_{cp}$$ N cp parameter, which is proportional to the total number of Cooper-Pairs formed at a temperature $${T}_{c}$$ T c . The $${N}_{cp}$$ N cp parameter allows an approach to the understanding of the Nb $${T}_{c}$$ T c anomalies, measured around 5 and 50 GPa.

In this work, we prepared TiO2 and Co multilayer thin films via DC magnetron sputtering method on (100) GaAs and (100) Si substrates. The power for each target (TiO2 and Co), deposition time of the layers, and pressure during deposition were kept constant. From XRD, Raman, and IR measurements, the formation of the ruffle and triclinic Co phases were identified in the multilayer thin films. An annealing process was carried in situ on all samples and subsequent to the deposition stage during 2 h. The substrate used was GaAs and Si wafer, favoring the formation and growth of the found phases. The diffusion and interdiffusion of the layers in the thin films were determined from Rutherford Backscattering Spectroscopy (RBS). In particular, Co and Ga were observed to associate after the annealing process according to the depth profiles. Due to the interdiffusion layers, the parallel magnetic contribution is not significant in the bilayer. Curves I-V of the Co/TiO2 bilayer showed the presence of resistive switching, according to the bipolar resistive. A correlation between synthesis parameters and the physical properties of the multilayers is presented.

In this work, a detailed study of structural, electrical and magnetic characterization of (GaMn)Sb diluted magnetic semiconductors (DMS) is presented. (GaMn)Sb thin films were grown by DC magnetron co-sputtering method as an innovative procedure to fabricate III-V DMS. The presence of unusual Mn2Sb2 and Mn2Sb secondary phases, induced by substrate temperature and deposition time, were revealed through XRD measurements. Magnetization measurements allow determining crossover between a paramagnetic-like to a ferromagnetic-like behavior controlled by secondary phases. It was found that both, the magnetic remanence and magnetic coercivity, increases with substrate temperature. Interestingly, the magnetic response is paramagnetic at lower deposition times and substrate temperatures, and XRD measurements suggest the absence of Mn2Sb and Mn2Sb2 in secondary phases. For longer deposition times or higher substrate temperature, XRD shows the presence of Mn2Sb2 and Mn2Sb phases and ferromagnetic-like behavior. The DC resistivity of our samples was characterized and the carrier density was determined by Hall measurements and, in contrast with the reported in other studies, found them to be a p-type semiconductor with carrier densities as big as one order of magnitude larger than reported values. From the ferromagnetic-like samples, evidence of an anomalous Hall-effect in the sample was found, with higher magnetic saturation and a anomalous Hall conductivity of 2380 S/cm. All the results point to a contribution of the secondary phases to the overall magnetic response of the samples used, and suggest the importance of studying the formation of secondary phases in the growth of DMS, especially, for the case of (GaMn)Sb where Mn ion can have multiple oxidation states.

This work presents an analysis of the functional derivative of the superconducting transition temperatureTcwith respect to the electron-phonon coupling functionα2F(ω) [δTc/δα2F(ω)] andα2F(ω) spectrum of H3S (Im3̄m), in the pressure range where the high-Tcwas measured (155-225 GPa). The calculations are done in the framework of the Migdal-Eliashberg theory. We find for this electron-phonon superconductor, a correlation between the maximums ofδTc/δα2F(ω) andα2F(ω) with its higherTc. We corroborate this behavior in other electron-phonon superconductors by analyzing data available in the literature, which suggests its validity in this type of superconductors. The correlation observed could be considered as a theoretical tool that in an electron-phonon superconductor, allows describing qualitatively the proximity to its highestTc, and determining the optimal physical conditions (pressure, alloying or doping concentration) that lead to the superconductor reaching its highestTcpossible.

In this work, porous-silicon samples were prepared by electrochemical etching on p-type (B-doped) Silicon (Si) wafers. Hydrofluoric acid (HF)-ethanol (C2H5OH) [HF:Et] and Hydrofluoric acid (HF)-dimethylformamide (DMF-C3H7NO) [HF:DMF] solution concentrations were varied between [1:2]-[1:3] and [1:7]-[1:9], respectively. Effects of synthesis parameters, like current density, solution concentrations, reaction time, on morphological properties were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements. Pore sizes varying from 20 nm to micrometers were obtained for long reaction times and [HF:Et] [1:2] concentrations; while pore sizes in the same order were observed for [HF:DMF] [1:7], but for shorter reaction time. Greater surface uniformity and pore distribution was obtained for a current density of around 8 mA/cm(2) using solutions with DMF. A correlation between reflectance measurements and pore size is presented. The porous-silicon samples were used as substrate for hydroxyapatite growth by sol-gel method. X-ray diffraction (XRD) and SEM were used to characterize the layers grown. It was found that the layer topography obtained on PS samples was characterized by the evidence of Hydroxyapatite in the inter-pore regions and over the surface.

We studied the electrical, magnetic, and transport properties of ( GaMn) Sb thin films fabricated by the direct current magnetron co-sputtering method. Using X-ray powder diffraction measurements, we identified the presence of ferrimagnetic ( Mn2Sb) and ferromagnetic ( Mn2Sb2) phases within the films. We also measured the magnetization of the films versus an applied magnetic field as well as their hysteresis curves at room temperature. We determined the electrical and transport properties of the films through temperature-dependent resistivity measurements using the Van Der Pauw method. The main contribution to the transport process was variable range hopping. Hopping parameters were calculated using percolation theory and refined using the diffusional model. In addition, we determined that all samples had p type semiconductor behavior, that there was an increase in the density of localized states near the Fermi level, and that the binary magnetic phases influenced the electrical properties and transport mechanisms. (C) 2016 Elsevier B. V. All rights reserved.

This work presents the results of synthesis and characterization of polycrystalline [Formula: see text]-type Bi2S3thin films. The films were grown through a chemical reaction from co-evaporation of their precursor elements in a soda-lime glass substrate. The effect of the experimental conditions on the optical, morphological structural properties, the growth rate, and the electrical conductivity [Formula: see text] was studied through spectral transmittance, X-ray diffraction (XRD), atomic force microscopy (AFM) and [Formula: see text] versus [Formula: see text] measurements, respectively. The results showed that the films grow only in the orthorhombic Bi2S3bismuthinite phase. It was also found that the Bi2S3films present an energy band gap [Formula: see text] of about 1.38 eV. In addition to these results, the electrical conductivity of the Bi2S3films was affected by both the transport of free carriers in extended states of the conduction band and for variable range hopping transport mechanisms, each one predominating in a different temperature range.

We have carried out first-principles spin polarized calculations to obtain comprehensive information regarding the structural, magnetic, and electronic properties of the Mn-doped GaSb compound with dopant concentrations: x = 0.062, 0.083, 0.125, 0.25, and 0.50. The plane-wave pseudopotential method was used in order to calculate total energies and electronic structures. It was found that the MnGa substitution is the most stable configuration with a formation energy of ∼1.60 eV/Mn-atom. The calculated density of states shows that the half-metallic ferromagnetism is energetically stable for all dopant concentrations with a total magnetization of about 4.0 μB/Mn-atom. The results indicate that the magnetic ground state originates from the strong hybridization between Mn-d and Sb-p states, which agree with previous studies on Mn-doped wide gap semiconductors. This study gives new clues to the fabrication of diluted magnetic semiconductors.

In this work, results are reported concerning the effect of the deposition parameters on the structural properties of Cu2ZnSnSe4 (CZTSe) thin films, grown through a chemical reaction of the metallic precursors by co-evaporation in a two-stage process. XRD measurements revealed that the samples deposited by selenization of Cu and Sn grow in the kesterite phase (CZTSe), respectively. Effect of the deposition temperature and mass ratio Cu/ZnSe on the transport properties of CZTSe films were analyzed. It was also found that the electrical conductivity of the thin films is affected by the transport of free carriers in extended states of the conduction band as well as for variable range hopping transport mechanisms, each one predominating in a different temperature range. The molecular and morphological effect on the compound through Raman and AFM measurements was studied. (C) 2016 Elsevier B.V. All rights reserved.