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In this paper, iron (III) oxide thin films are deposited on glass substrate via sol-gel dip coating by increasing withdrawal speeds in the range 100–250 mms \(^{-1}\) . Prepared thin films were characterized by UV-VIS spectrophotometer, spectroscopic ellipsometry (SE), X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and Fourier transform infrared (FTIR) spectroscopy. UV-VIS spectrum and SE show decrease in bandgap energy from 2.8 to 1.6 eV with increased withdrawal speed. FTIR results indicate formation of \(\alpha \) -Fe2O3 (hematite) phase of iron oxide with preferred orientation along (104) plane. From SEM studies, it is observed that the developed \(\alpha \) -Fe2O3 films are nanocrystalline with small grain size. The surface of \(\alpha \) -Fe2O3 films is smooth and homogenous, which also supports the XRD results. VSM results show that \(\alpha \) -Fe2O3 thin films have ferromagnetic behavior. [ABSTRACT FROM PUBLISHER]

Manganese copper ferrites belong to a family of ferrites with specific importance due to their high permeability values and low losses at low frequencies. In this paper, a series of ferrite samples has been synthesized using a novel and low cost sol-gel autocombustion route in order to systematically investigate the structural, compositional, morphological, and magnetic properties when zinc is substituted by copper in the series. X-ray diffraction reveals that all the samples have characteristic cubic spinel structure. The effect of zinc substitution at the copper site on the chemical bonding of the ferrite samples was investigated by Fourier transform infrared spectroscopy. Energy dispersive X-ray analysis was performed to determine the homogeneity and stoichiometric composition of elements present in the samples. Nanosized, uniformly shaped grains were evident from the images obtained using a scanning electron microscopy, which indirectly confirms the significance of the autocombustion synthesis technique employed in this paper. Magnetic properties determined using a vibrating sample magnetometer exhibited that zinc substitution could enhance the saturation magnetization of the samples, attributed to the substitution of a paramagnetic element (zinc) by a diamagnetic one (copper). [ABSTRACT FROM PUBLISHER]

In this paper, \beta -Ga2O3 thin films were grown on a p-Si substrate using the sol–gel method. Structural characterization of the films was performed using X-ray diffraction. Electrical parameters such as breakdown field, interface traps density ( {D}_{\text {it}} ), and series resistance ( {R}_{s} ) were investigated at room temperature. The interface trap density was found to be 10^12 eV ^-1 cm ^-2 using the Hill–Coleman method. This result is valuable for MOS capacitor applications. Dielectric parameters were investigated in the wide frequency range (20 kHz–1 MHz) at room temperature. We observed that these parameters have a strong dependence on frequency and voltage. [ABSTRACT FROM PUBLISHER]

In this paper, an efficient room temperature ethanol sensor device based on p-n homojunction of p-TiO2 nanoparticles (NPs) and n-TiO2 nanotubes (NTs) is reported. p-TiO2 NPs were prepared by low-temperature sol–gel method and coated on n-TiO2 NTs (NPs) grown by electrochemical anodization. Field emission scanning electron microscopy and X-ray diffraction authenticated the formation of stable homojunction between p-type anatase TiO2 NPs and n-type anatase TiO2 NTs. Current–voltage characteristics of the device, in the lower voltage range (0–1.26 V) for 30 °C, followed nonlinear characteristics (Schottky). With increase in voltages (>1.26 V) and temperature (40 °C–100 °C) such nonlinear behavior moves toward more linear ones. The gas sensing performance of the homojunction device was studied at room temperature with alcohols as the test species. The device offered the maximum response magnitude of ~57% (toward ethanol) at 100 ppm with appreciably fast response time and recovery time of ~30 and ~16 s, respectively. Dramatic increase in the effective depletion region area distributed throughout the nanotubular voids and the associated localized electric filed originated from the electrostatic charge separation therein (which helps in easy dissociation of target species) is possibly responsible for such efficient room temperature sensing performance. [ABSTRACT FROM AUTHOR]

In this paper, Fe-doping TiO2 was introduced into a dielectric barrier discharge (DBD) process for catalytic nonthermal plasma (NTP) degradation of a mode organic pollutant reactive blue (KN-R). Plasma was generated in a DBD reactor; Fe-doping TiO2 was prepared by the sol-gel process. The catalytic-NTP oxidation reactions were studied under various conditions including the examination of the effects of initial pH, KN-R concentrations, and catalyst dose. Typical results indicated the synergy between plasma excitation of KN-R followed by the catalytic action of Fe-doping TiO2, which not only improved the conversion but also increased the mineralization efficiency. The determination of hydrogen peroxide and nitrate ions, and ultraviolet–visible absorption and Fourier transform infrared spectra analyses revealed that catalysts in a plasma system strengthen the mineralization of KN-R. [ABSTRACT FROM PUBLISHER]

High-performance ultraviolet (UV) Schottky photodiodes obtained by growing Pd Schottky contacts on the sol-gel-derived n-ZnO thin films deposited on n-Si substrates have been reported in this paper. The current-voltage ( I – V ) measurements of the as-fabricated Schottky photodiodes show an excellent room temperature contrast ratio (i.e., the ratio of the current under UV illumination to the dark current) of \sim 5.332\times 10^3 and responsivity (i.e., the parameter characterizing the sensitivity of the device to the UV light) of \sim 8.39 A/W at −5 V reverse bias voltage, respectively; when the device is illuminated by an UV source of \sim 650~\mu \textW output power at $\sim 365$ nm. The measured room temperature contrast ratio and responsivity are believed to be the highest among the reported values in the literature for ZnO thin film-based Schottky photodiodes using sol-gel method. [ABSTRACT FROM AUTHOR]

In this paper, the effects of N2O plasma treatment (PT) at various temperatures on the performances of InMgZnO (IMZO) thin-film transistors (TFTs) were investigated. As a result, the TFTs with N2O plasma-treated (10 W) IMZO channel layers at 100° for 10 min showed five times higher linear field-effect mobility compared to the untreated IMZO. The N2O PT did not cause any significant changes to the crystal structure, surface roughness of the IMZO thin films. However, an X-ray photoelectron spectroscopy study confirmed that the oxygen-vacancy defect density of the channel layer decreases via the N2O PT with temperature increased, and the reduction of oxygen vacancies leads to a decrease of off-current (IOFF). It was found out that the refractivity of the channel layer increases with PT temperature increased, and the improvement of the film density makes the on-current (ION) higher, resulting in high mobility and high I \mathrm{\scriptscriptstyle ON}/I \mathrm{\scriptscriptstyle OFF} ratio. Our study suggests that moderate N2O PT temperature can be adopted to improve the device performances. [ABSTRACT FROM PUBLISHER]

ZnO:Ga (GZO)/Si photodiodes having different thicknesses of GZO layer are fabricated by the sol–gel spin-coating method. The photoelectric properties of the devices are investigated by measuring the current–voltage (I–V) characteristics. The photodiodes exhibit high rectification ratio (RR) and relatively low leakage current. Moreover, the best performance of the photodiodes is achieved by the heterojunction with GZO thickness of 35 nm, which has a transmittance over 87% in the visible range, compared to others. The resulting device shows a current RR of 1275 at ±3 V, a low saturation current ($\text{I}_{\text {s}}$) of $3\times 10^{\text {-8}}$ A, and a photocurrent-to-dark-current ratio of 4639 at −3 V under 100 mW/cm2. [ABSTRACT FROM AUTHOR]

In this paper, we are proposing a novel rapid sol–gel thin-film porous metal–oxide-based surface acoustic wave (SAW) humidity sensor. For the SAW sensor, the center frequency of 433.92 MHz has been selected, and the device has been configured in a high-frequency oscillator circuit to explore the frequency response in the presence of water vapor. The sensitive thin film of sol–gel $\gamma $ -Al2O3 coated with a drop dry method offers very high surface-to-volume ratio with the distribution of micropores making the sensor highly sensitive for moisture detection. Pore morphologies of the film have been studied by field emission scanning electron microscope and atomic force microscopy. The \gamma $ phase of alumina of the film has been characterized with X-ray diffraction. The sensor has been tested from 3% relative humidity (RH) to 85% RH. The proposed sensor has very fast ( T_{r}= 1 s) response time and excellent yield ratio in comparison with the conventional commercial capacitive aluminum oxide sensor. The sensitivity (3%–20% RH) and the hysteresis (3%–85% RH) are found to be 120-Hz/% RH and 0.3%, respectively. The sensor can be useful for different applications, including moisture dispersion inside electronic gadgets, dryers, ovens, textile production, semiconductor device processing, food processing, medicine, and sealed packages. [ABSTRACT FROM PUBLISHER]

The effect of N and Cr doping on the magnetic properties of TiO2 nanoparticles is analyzed in this paper. N- and (Cr, N)-doped TiO2 nanoparticles were synthesized by the sol–gel method using titanium tetraisopropoxide as metallic precursor, and urea and chromium nitrate as N and Cr doping precursors, respectively. The calcined nanoparticles were analyzed through X-ray diffraction and Rietveld refinement. The samples display an anatase structure with mean grain sizes $\sim5$ nm. A distortion of the anatase cell is detected (increase and decrease of $a$ and $c$ lattice parameters, respectively) with respect to the reported anatase bulk values. The room-temperature hysteresis loops of the samples display the coexistence of the paramagnetic and the ferromagnetic contributions. An enhancement in the ferromagnetic component is observed upon Cr and N codoping. The analysis of the temperature dependence of the magnetization confirms the coexistence of both the paramagnetic and the ferromagnetic contributions. Although the existence of a secondary phase cannot be completely excluded in the (Cr, N)-doped sample with the highest nitrogen content, the results confirm the achievement of intrinsic room temperature ferromagnetism in these doped semiconductor nanostructures. [ABSTRACT FROM AUTHOR]

In this paper, the temperature-dependent electron spin resonance and magnetization ( M ) studies of La0.7−xBixCa0.3MnO3 ( x= 0 , 0.35, 0.42, 0.56, and 0.63) manganites synthesized by the sol–gel method are reported. In all the samples, the coexistence of paramagnetic and ferromagnetic phases over a wide range of temperature is observed. The estimated Curie temperature ( T_{C} ), the Curie–Weiss temperature ( \theta _{C} ), and the temperature at which linewidth ( \Delta H ) becomes minimum ( Tmin ) decrease with the increase in the Bi content. The decreasing trend of these parameters is discussed in view of the difference in the ionic radii of La3+ and Bi3+ and the variations in 6s2 lone pair character of Bi3+ ions with the increase in the Bi content. The evolution of various types of magnetic interactions as a function of temperature and Bi content is discussed. [ABSTRACT FROM AUTHOR]

A newly developed semi-fixed flexible polishing tool called sol-gel (SG) polishing pads can satisfy the polishing demand of silicon wafers with scratch-free and nano-roughness surface. However, an obvious damage layer emerges on the surface of monocrystalline silicon wafer after polished by SG polishing pads with diamond abrasives. In this paper, combined characterizations consist of grazing incidence X-ray diffraction, Raman spectroscopy (RS), focused ion beam-scanning electron microscopy (FIB-SEM), transmission electron microscopy (TEM), and SEM were used to observe the damage layer together with the polishing residue. The results indicated that the surface monocrystalline silicon transformed to \boldsymbol \alpha -Si and nano-Si. Analysis on the polishing processes under the same experimental parameters with different tools and abrasives revealed that the material removing scale about 100–300 nm may account for the generation of damage layer. [ABSTRACT FROM AUTHOR]

Mn/Fe co-doped ZnO thin films are prepared by simple sol–gel and spin coating method. Five different sols with the change in concentration (1–5 wt%) of both Mn and Fe are synthesized. Molar ratio of Mn and Fe is kept constant, i.e., 1:1. Sols are spun onto glass and copper substrates by spin coating method followed by the post magnetic field annealing at 300 °C for 1 h. Effect of Mn and Fe codoping on ferromagnetic properties of ZnO is reported in this paper. Structural and magnetic properties of as prepared and annealed samples are investigated by X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). Scanning electron microscope is used to study the surface morphology of co-doped films. XRD results show incorporation of Mn and Fe in the host lattice upto a dopant concentration of 4 wt%. However, small crystallites of Mn and Fe2O3 are observed by increasing the dopant concentration to 5 wt%. VSM results indicate room temperature ferromagnetism in all samples without the presence of any secondary phases. Low value of shape anisotropy is observed in the case of Mn doped ZnO. However, no shape anisotropy is observed in the case of co-doped thin films. Moreover, Mn/Fe co-doped thin films show magnetic hysteresis equivalent to that of multilayered structure, indicating that such complex structures used in spintronic devices can be replaced by a single ZnO layer with codoping of Mn and Fe. [ABSTRACT FROM PUBLISHER]

Doping effects of acidic (pH4) and basic (pH10) Fe3O4 on the magnetic properties of ZrO2 have been reported in this paper. Fe3O4 doped zirconia (FZ) sol is synthesized by varying Fe3O4 concentrations in the range of 2–10 wt% using sol-gel route. FZ sols are spin coated onto glass substrates and then vacuum annealed at 300 °C for 60 min in the presence of 500 Oe magnetic field. X-ray diffraction results show amorphous behavior at 2 wt% doping in both acidic and basic cases. Mixed monoclinic-tetragonal behavior is observed in acidic films with 6–10 wt% doping concentration. However, tetragonal phase is observed in basic films with 8–10 wt% doping. Soft ferromagnetic behavior is observed in both the acidic and basic doped zirconia. Saturation magnetization (M \(_{\mathrm {s}}\) ) of \(\sim 33\) emu/g is observed in acidic FZ samples whereas, variation in M \(_{\mathrm {s}}\) (1–36 emu/g) is observed in basic FZ samples. Iron oxide stabilized ZrO2, with soft ferromagnetic behavior, can be employed for coatings on teeth as well as for diagnosis and therapy of oral cancer. [ABSTRACT FROM PUBLISHER]

Metal acetylacetonates are conventional sol-gel precursors used to deposit thin amorphous metal oxide films of In–Zn–O (IZO) suitable for thin-film field effect transistors (TFTs). In this paper, we couple this traditional approach with a postdeposition UV-ozone treatment to effectively reduce carbon impurities prior to any thermal treatment steps. Therefore, we find that the rate of bulk metal oxide formation is enhanced, thus enabling a significant reduction of the processing temperature necessary to achieve high-mobility transistors. Optimized TFT structures processed at 300^\circC show n-type mobility of 35 cm^2/Vs with on and off ratio of 10^7. Moreover, positive bias stress tests of such devices are found to exhibit one the lowest threshold voltage shifts of any solution-processed amorphous TFT fabricated without a passivation layer. [ABSTRACT FROM PUBLISHER]

In this paper, we report the electron spin resonance (ESR) studies of Bi1 - xCaxMnO3 (0.65 \leq x \leq 0.90) samples synthesized by sol-gel technique. From the temperature dependent ESR data, double integrated intensity (DI), linewidth (\DeltaH) and resonance field (Hr) values of the ESR signal have been used to get information about magnetic interactions. The charge ordering (TCO), antiferromagnetic (AFM) ordering, i.e., Neel temperature (TN) values are estimated within \pm3 K of experimental error for all the samples. The estimated TCO values are 288, 302, 219, and 220 K for x = 0.65, 0.70, 0.75, and 0.80 samples, respectively. The charge ordered state is suppressed for samples with x = 0.85 and 0.90. The estimated TN values are 139, 128, 139, 132, 126, and 126 K for x = 0.65, 0.70, 0.75, 0.80, 0.85, and 0.90, respectively. For the samples with 0.65 \leq x \leq 0.80, the ferromagnetic (FM) interactions dominate in the temperature range T > TCO. Whereas for x = 0.85 and 0.90 samples, the existence of AFM superexchange interactions and localized FM-AFM transition are evident. The FM and AFM correlations coexist in the temperature range TN < T < TCO. [ABSTRACT FROM PUBLISHER]

Sn–Zn–Co-substituted strontium M-type hexaferrite SrZnxCoxSn2xFe12–4xO19 ($x =0.0$ , 0.3, 0.5, and 0.7) was synthesized via modified sol–gel auto-combustion method. A microwave device was used to obtain the finest particles and to complete the combustion process. By substitution of tetravalent and divalent cations instead of iron, magnetic and structural properties of M-type hexaferrite were changed. So, the effects of Sn4+, Zn2+, and Co2+ doping on the structure and magnetic characterization of M-type hexaferrite were investigated. The Fourier transform infrared spectroscopy revealed bands at 430 and 590 cm−1, related to the stretching vibrating bonds of Fe–O. The X-ray diffraction analysis showed that all samples prepared were of P63/mmc symmetry and average crystal size of 68 nm. Field emission scanning electron microscopy analysis revealed the hexagonal plateletlike shape of all samples. Vibrating sample magnetometer results showed that by increasing the dopants content, coercivity ($H_{c}$), and saturation magnetization ($M_{s}$) changed drastically. Saturation magnetizations decreased during dopants displacement and then reach to the highest value (65.46 emu/g) at $x = 0.5$ then increasing of dopants to $x = 0.7$ , cause the reduction of $M_{s}$ (56.13 emu/g). Coercivity diminished by dopant substitution and the semi-hard samples were received as an alternative to the hard hexaferrite. [ABSTRACT FROM AUTHOR]

Complementary resistive switches (CRS) based on back-to-back nanofilamentary resistive RAM devices have been fabricated by an all-solution-processed method, employing inkjet-printed Ag and Au contacts and a spin-coated sol–gel zirconium oxide dielectric layer. The devices demonstrate electrical switching behavior below 3 V, stable on-state windows, reasonable cycle lifetimes, and can be implemented in $2\times 2$ memory arrays with no crosstalk during addressing. For reliable operation and high yields of the CRS devices, printing and annealing processes were carefully optimized to eliminate the coffeering effect on the bottom electrode, and produce a pin-hole free dielectric. The arrays are fully pulse programmable and are able to retain their state for > 10^{4} s. Additionally, the arrays can be operated as associative or content addressable, memory for pattern matching applications, which is demonstrated through a basic hamming distance mapping measurement for different stored data states. [ABSTRACT FROM PUBLISHER]

Magnetic Fe3O4@SiO2 nanoparticles were initially synthesized by a sol-gel process and introduced to a soft magnetic carbonyl iron particle-based magnetorheological (MR) fluid to improve its MR properties and dispersion stability. Structure and properties of the core–shell Fe3O4@SiO2 nanoparticles were characterized, showing that they are soft magnetic. MR characteristics of two MR fluid systems with and without Fe3O4@SiO2 additives were investigated and compared under different magnetic field strengths using a rotational rheometer, exhibiting typical MR behaviors. Dispersion stability of the MR fluid was also characterized by an optical analyzer system of Turbiscan. [ABSTRACT FROM AUTHOR]

Using citric acid, ferric nitrate, and ammonia as starting materials, magnetite (Fe3O4) powders were successfully synthesized through a low-temperature sol–gel autocombustion method. The molar ratios $\Phi $ of citric acid to ferric nitrate were adjusted from 0.1:1 to 1.5:1. The combustions were activated at a temperature as low as 300 °C. The X-ray diffraction was used in the determination of the phases of the prepared samples. The results illustrate that some of the as-prepared samples have pure Fe3O4 phase. Magnetite can be synthesized within a large range of molar ratio of citric acid to ferric nitrate. Scanning electron microscopy studies show us porous characteristics of the prepared samples. The results of vibrating sample magnetometer studies show us ferrimagnetic properties of the as-prepared magnetite products at room temperature with a maximum saturation magnetization as high as 91 emu/g. The magnetic hysteresis loops reveal soft magnetic properties of these materials. The saturation magnetization value of the sample of $\Phi =0.5$ is about 99% of the corresponding bulk value, which indicates that $\Phi =0.5$ is the most suitable molar ratio for the experiment. [ABSTRACT FROM AUTHOR]

MnZn ferrite nanoparticles (NPs) with MnxZn1–xFe2O4 ( $x=0$ and 0.6) compositions have been synthesized by sol–gel process. As prepared (AP) particles were annealed at 1200 °C in air to compare the physical properties of NPs with their bulk counterparts. The crystallite sizes of AP samples were estimated to be 18 nm for x=0$ and 11 nm for x=0.6$ . The cationic disorder was evaluated from the Rietveld analysis of X-ray diffraction (XRD) data, which decreases with increasing annealing temperature. The average particle size of the AP samples is observed to be below 20 nm and transform into single-phase spinel structure of \sim 500$ nm long cylindrical rods of 60 nm-diameter for x=0.6 and superparamagnetic behavior above the T_{B} . The observed magnetic characteristics corroborate well with the structural parameters obtained from the Rietveld analysis of the XRD data. [ABSTRACT FROM AUTHOR]

The modification of multispin casting multilayered barium titanate (BTO) thin films on indium tin oxide (ITO)/glass substrate without doping other elements is adopted to improve the memory performance. The X-ray photoelectron spectroscopy analysis reveals the concentration of oxygen vacancies can be reduced by the increasing number of the BTO layer. Mechanisms of conducting paths relating to the concentration of oxygen vacancies will also be explicated. The memory devices showed typical bipolar resistive switching behavior and an ON/OFF ratio of over 10^\mathrm \mathbf 6 . The memory devices also exhibited outstanding uniformity. A retention time of over 10^\mathrm \mathbf 5 s without fluctuation at room temperature and 85 °C can be achieved. [ABSTRACT FROM AUTHOR]

Fe2O3 nanoparticles are synthesized chemically by sol–gel method. The nanoparticles have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermo gravimetric analysis/differential thermal analysis-differential scanning calorimetry (TGA/DTA-DSC), and vibrating sample magnetometer (VSM). XRD results identify hematite phase of iron oxide nanoparticles. The average crystalline size of the nanoparticles increased from 34 to 36.7 nm when the annealing temperature increased from 400 °C to 1000 °C. FTIR technique also confirmed XRD results. Phase transformation temperatures were determined by DSC–TGA. The exothermic peak at 720.2 °C is attributed to the phase change from \(\gamma \) Fe2O3 (low temperature phase) to \(\alpha \) Fe2O3 (high temperature phase). The annealing temperature also affects the optical properties since the measured band gap increased from 2.4 to 2.7 eV when the annealing temperature increased from 400 to 1000 °C. [ABSTRACT FROM PUBLISHER]

We here report the preparation of undoped BiFeO3 (BFO) thin films with sol-gel method using two solvents, i.e., acetic acid (AA) and ethylene glycol (EG). Films are annealed in the temperature range 100–300 °C for 60 mins. Films deposited using AA show the presence of bismuth rich phase Bi46Fe2O72 along with BFO in the intermediary conditions. Pure phase BFO is obtained when films are deposited using EG as a solvent even under as-deposited conditions, and the pure phase persists after annealing in the temperature range 100 °C–300 °C. This is the lowest temperature reported for the preparation of phase pure BFO. Bandgap of AA-based films lies in the range 2.58–2.64 eV and that of EG-based films in the range 2.77–2.81 eV. Reduced value of dielectric constant, in AA-based films, is because of the presence of bismuth rich impurity phase as compared with the films prepared using EG. Bands in FTIR spectra at 487 and 552 cm \(^{-1}\) are characteristic bands of FeO6 and BiO6 groups, indicating the formation of BFO. Films deposited using AA show weak ferromagnetic behavior, while those deposited using EG show strong ferromagnetic behavior as opposed to antiferromagnetic nature of BFO, due to suppression of spiral spin structure. [ABSTRACT FROM PUBLISHER]

Co-doped zinc oxide thin films (ZnCoO) have been deposited on glass substrates by sol–gel dip coating deposition method. X-ray diffractometer patterns for these thin films prove crystalline behavior with wurtzite structure. The films have lattice parameters similar to that of ZnO. When Zn is replaced by Co, more impurity levels are produced within the bandgap, and more defects are developed. However, Co-doping does not alter the wurzite structure. The bandgap of the films tends to decrease with increasing withdrawal speed. These transparent thin films possess bandgap in the ultra-violet (3.86–3.45 eV) and high transparency throughout the visible spectral region. Ellipsometry also show the same trend for bandgaps (3.83–3.45). Morphological analysis by scanning electron microscope shows surface with porous structure. Magnetic property studied shows the ferromagnetic behavior. Chemical composition of these Co-doped ZnO thin films was investigated through Fourier transform infrared analysis. [ABSTRACT FROM PUBLISHER]

A series of single-phase nanocrystalline Mn0.5Cu0.5−xNixFe2O4 spinel ferrites with \(x = 0, 0.1, 0.2, 0.3, 0.4,~{\rm and}~0.5\) was successfully synthesized by sol-gel autocombustion method, at a temperature as low as 300 °C. X-ray diffraction, scanning electron microscopy, and room-temperature vibrating sample magnetometry studies have been carried out in order to understand the structural, morphological, and magnetic properties as a function of nickel concentration. The lattice parameters did not show any consistent decreasing or increasing trend, but crystallite size was decreased due to the incorporation of Ni contents at Cu sites in the structure. Large-sized grains were evident for the composition Mn0.5Cu0.5Fe2O4; however, the grain size was significantly reduced as the Ni was substituted. It was observed that with increasing nickel concentration, saturation magnetization increased, but coercivity decreased, which could be attributed to the substitution of soft ferromagnetic Ni2+ ions in place of diamagnetic Cu2+ ions. [ABSTRACT FROM PUBLISHER]

Structural and magnetic properties of NiCrxFe2−xO4( \(x=0.7\) and 0.9) spinel ferrites prepared by sol-gel route have been investigated using synchrotron X-ray powder diffraction (SXPD) and magnetization measurements. The gel products after annealing at 1000°C for 2 h are found to crystallize in cubic phase. Rietveld refinements of X-ray diffraction and SXPD patterns revealed that the compounds are almost perfect inverse spinel with only few percents of nickel atoms located at the tetrahedral sites. Transmission electron microscopy (TEM) images showed that the samples are composed of nanoparticles with mean diameter in agreement with crystallite size determined by the Rietveld analysis. The spontaneous magnetization \(M_{s}\) as a function of temperature was determined via magnetization curves measured using vibrating sample magnetometer in a temperature range from 88 K to above Curie temperature in applied fields up to 10 kOe. The sample \(x=0.9\) shows a cancelation of sublattice magnetizations at 400 K. The temperature dependence of saturation magnetization \(M_{s}\) of the samples can be described in terms of molecular-field model for collinear spins with the derived cation distributions. [ABSTRACT FROM AUTHOR]

Bilayered perovskite manganites of the composition La1.25Sr1.75Mn2O7 (LSMO) were synthesized successfully by the sol–gel method. The effects of pH concentration, calcination temperature, and time on the phase formation, structure, and magnetic properties of the material were systematically investigated. X-ray diffraction and Rietveld refinement analysis revealed that the single phase of LSMO was only obtained in samples sintered at a temperature as high as 1250 °C. The best magnetic properties were achieved in samples with \({\rm pH} = 7\) , calcinated at 1450 °C for 10 h. Our studies show that the pH concentration, calcination temperature, and time are important factors in tailoring the magnetic properties of double-layered perovskite manganites. [ABSTRACT FROM AUTHOR]

Ce^3 + doped lutetium aluminum garnet (Ce:Lu3Al55O12/Ce:LuAG) Polycrystalline scintillation films have been fabricated on silicon (111) substrates by Pechini sol-gel method combined with spin-coating technique. Photoluminescence (PL) spectra and X-ray absorption fine structure (XAFS) analysis were used to characterize the as-prepared films. X-ray absorption near-edge structure (XANES) spectra of the Ce–L_3 edge demonstrated that the Ce ion in Ce:LuAG films synthesized in air exhibited two charge states, + 3 and + 4 valence respectively. By post annealing in H_2 atmosphere, the relative content of Ce^3 + ions increased from 46.3% to 80.5% for 1.0 mol%Ce:LuAG films, which corresponded with the enhancement of luminescence intensity of this samples. [ABSTRACT FROM PUBLISHER]

The effects of sol-gel treatment and plating on the electrical properties of multilayer filters were investigated. The results showed that the sol-gel treatment process can effectively lower the apparent porosity of multilayer filters, preventing the penetration of electroplate liquid into the filters. The mean insertion loss rise for the sol-gel-treated components was 0.171 dB, which increased up to 0.811 dB for the filters without sol-gel seal treatment. Microstructural studies revealed that the sol-gel seal treatment is an effective preplating treatment to diminish the insertion loss of multilayer filters. [ABSTRACT FROM PUBLISHER]

The nitrogen substituted bismuth ferrite polycrystal sample BiFeO2.1N0.9 has been successfully synthesized using sol–gel method. Its structural and magnetic properties are investigated. The formation of Fe4+ due to charge compensation is found in BiFeO2.1N0.9 from X-ray photoelectron spectra. The crystal structure of BiFeO3 is barely affected by N doping while the magnetic property is well improved. We propose that it is the coexistence of different superexchanges (Fe–N–Fe and Fe–O–Fe) that breaks the magnetic cancellation effect of the spin spiral, hence increasing the macroscopic magnetization. [ABSTRACT FROM AUTHOR]

We demonstrate the electronic trap energy distribution (Δ EIL) in the wide bandgap, nonconventional aluminum oxide phosphate (ALPO) dielectrics. The trap energy distribution has been measured by using the gate injection high-speed capacitance–voltage measurement technique and verified through conventional deep-level transient spectroscopy. The electronic trap energies in ALPO dielectrics were found to be influenced and, hence, tunable by the irradiation temperature. The nonirradiated dielectric film (NI-ALPO) displayed the maximum number of electronic traps at an energy level of 0.2 eV below the conduction band of silicon (Si-ECB). On the other hand, the dielectric film irradiated at 200 °C confirmed the highest number of traps at the location of 0 eV and at the same energy level of Si-ECB. In addition, the NI-ALPO dielectric contained over 90% of traps in the deep level of the bandgap (below Si-ECB). In contrast, the ALPO film irradiated at 200 °C accommodated a limited number of traps (~75%) at the deep level of the bandgap. [ABSTRACT FROM AUTHOR]

In this brief, the structural properties and sensing characteristics of spin-coated Ce2(Zr1–xTix)Oy (CZT) sensing film were investigated for electrolyte–insulator–semiconductor (EIS) pH sensors. A higher pH sensitivity of 64.42 mV/pH, a lower hysteresis voltage of 1.1 mV, and a smaller drift rate of 0.36 mV/h were achieved in the CZT-embedded EIS sensors at Zr/Ti = 53/47 stoichiometry. The higher sensing behavior in CZT is attributed to the good crystallization and higher surface roughness of the film. [ABSTRACT FROM PUBLISHER]

The National High Magnetic Field Laboratory (NHMFL), Tallahassee, FL, USA, has developed a 32-T all-superconducting user magnet system combining two series-connected high-field high-temperature superconductor (HTS) nested inner coils (insert) wound with SuperPower REBCO tapes and a low-temperature superconducting (LTS) outer magnet (outsert) composed of five coils (broken in 17 electrical sections). As a part of the magnet development work, a number of quench tests were done on the HTS insert dual-coil prototype in the actual LTS outsert, mimicking the actual magnet configuration and operation. The tests on the coupled insert/outsert system were performed at 4.2 K, using a set of tailor-made quench protection heaters to be employed in the actual insert. In these tests, in the transition to the normal state, a noticeable part of the outsert stored energy could be transferred to the insert through the inductive coupling. The experimental results are analyzed here by means of a quasi-3-D COMSOL FEM model. The model, developed at the University of Bologna in collaboration with the NHMFL, enables one to calculate the coil temperature distributions, the internal voltages, and current evolution through the increase of normal zone resistances over the insert coils. A lumped parameter equivalent model of the magnet electric circuit permits including appropriately the effect of mutual inductive coupling between the insert and the outsert coils on the currents in them. Also, the model accounts for a time-varying 2-D distribution of the magnet field generated by both the insert and outsert within their coils in the event of a quench. The REBCO insert coils are described in terms of an anisotropic homogenized medium, albeit with due regard for the essentially nonlinear characteristics of the superconducting tapes and for the interturn stainless steel reinforcement and sol-gel alumina insulation. A detailed comparison between the numerical and experimental results provides detailed insights into the modes of propagation of the normal zones. [ABSTRACT FROM PUBLISHER]

Efforts have been made by the researchers to enhance the sensitivity of a humidity sensor by selecting and fabricating different nanostructures thin films and optimizing their pore morphology. However, other characteristics, such as nonlinearity, hysteresis, reproducibility, response and recovery times, and selectivity, are equally important for real time measurement, monitoring, and controlling of humidity. It is reported that a low signal frequency is essential for enhanced sensitivity, but the effect of the signal frequency on other characteristics is rarely investigated. We have investigated the role of the signal frequency on the response characteristics of a nanostructure ceramic thin-film interdigitated electrode humidity sensor for the first time. Our studies show that although the sensitivity is high at low frequency, the performance of the sensor is highly nonlinear and frequency dependent. At high frequency above 100 kHz, the sensitivity is reduced, but other characteristics of the sensors are improved significantly. Improved characteristics are due to the reduced effect of double layer capacitance that plays a significant role for extreme sensitivity at low frequency. The effect of double layer capacitance is rarely considered for evaluating the response characteristics in the literatures. Results show that at 200-kHz frequency, nonlinearity and hysteresis are 9.39% and 16.77%, while at 100 Hz, these values are 5588% and 70.8%, respectively. Improve response characteristics will reduce the complexity of signal conditioning, particularly nonlinearity and hysteresis, the compensation of which is essential for almost all types of humidity sensors. [ABSTRACT FROM PUBLISHER]

Na, Mg and Al-doped ZnO nano-powders were prepared by the sol-gel method. Acetate of zinc and nitrate salts of Na, Mg and Al were mixed with solution of ethanolamine and 2-methoxyethanol. The xerogel was calcinated at 973 K for 1 h in the air to eliminate organic matter and form powders. The structural, the grain size of doped ZnO and photocatalvtic activity of the powders were investigated. The samples crystal structure were analyzed by XRD and photocatalytic activity were carried out in a UV-visible spectrophotometer. Photocatalytic degradation of the methyl orange solution under the light of wavelength of 254 nm was performed to investigate the photocatalytic activity of doped ZnO powders. The results showed that dopant can greatly improve the photocatalytic activity of ZnO powders. The enhancement of photocatalytic activity of doped ZnO powers is mainly due to their smaller particle size and capability for reducing the electron hole pair recombination. [ABSTRACT FROM AUTHOR]

Mn-Zn ferrite nanoparticles of Mn0.6Zn0.4Fe2O4 composition were synthesized through sol-gel auto combustion process. The phase formation, thermal stability, morphology, and magnetic properties of as-prepared and heat treated samples have been investigated. It is observed that as-prepared spherical particles (10–40 nm) transform into single phase spinal structure of \(\sim 500\) nm long cylindrical rods of 60 nm diameter, when annealed at 1200 °C in air. Interestingly, when the samples were annealed at 600 °C in air Fe2O3, Mn2O3 impurity phases appear along with poor quality ferrite phase. On the other hand, samples annealed at 600 °C, under inert gas conditions showed well-ordered single phase spinal structure with large \(\text{M}_{\mathrm {\mathbf {s}}} =60\) emu/g and \(\text{H}_{\mathrm {\mathbf {c}}} =55\) Oe. Furthermore, it is shown that on rapid cooling, the sample from 1200 °C yields a good quality spinel structure with enhanced soft magnetic properties ( \(\text{M}_{\mathrm {\mathbf {s}}} =62.3\) emu/g; \(\text{H}_{\mathrm {\mathbf {c}}} = 3\) Oe). [ABSTRACT FROM AUTHOR]

The study of on iron oxide, especially magnetite Fe3O4, in the form of thin films and nanostructures, is interesting due to its wide applications in data storage, biomedical, and spintronic devices. Seven different sols are synthesized with varying concentration from 1.8 to 0.6 mM using the sol-gel technique. The concentration of 1.4 mM results in a pure phase whereas others show mixed magnetite and maghemite phases. In addition, changes in film preferred orientation from (400) to (220) planes are responsible for changing the ferromagnetic behavior of films to ferrimagnetic with increased saturation magnetization. Free growth of iron oxide nanostructures, including nanoneedles and nanobrushes, are observed in scanning electron microscope images. [ABSTRACT FROM PUBLISHER]

Bismuth iron oxide (Bi1−xKxFeO3) thin films are prepared using sol-gel and the spin coating method. Films are deposited onto copper substrates and are annealed in the presence of vacuum with 500 Oe magnetic field at 300 °C. Potassium has an ionic radius of 1.64 Å and replaces Bi, which has an ionic radius of 1.17 Å. Based on the ionic radii difference of Bi3+ and K+, the dopant concentration is varied in the range \({ {{{x}} =}}~0.0\) –0.3. X-ray diffractometer analysis shows that at \({{x}} {=} {0.3}\) an impurity phase (K2O) appears, which was not present at low dopant concentrations. It is shown here that ferromagnetic behavior arises in doped BiFeO3 films due to suppression of helical spin structure. In addition, as K+ replaces Bi3+ the charge compensation mechanism gives rise to oxygen vacancies and to the formation of Fe4+ cations, thus inducing ferromagnetic behavior. Variation in dopant concentration strongly affects the dielectric properties. Increase in dielectric constant up to \(\sim 84\) was observed with increase in dopant concentration up to 0.15. Decrease in dielectric constant ( \(\sim 25\) ), beyond 0.15 doping concentration, might have been observed because of the appearance of impurity phase as is observed in structural and magnetic properties. [ABSTRACT FROM PUBLISHER]

Non-stoichiometric YAG powder samples were prepared via a simple sol-gel combustion method by introducing antisite defects YAl,16a intentionally. The investigation of structure and luminescence properties confirmed that the antisite defects with different concentrations can be created through adjusting the composition in YAG at relatively low (1000^\circC) temperature. The X-ray excited luminescence and vacuum ultra-violet spectroscopies show that the luminescence intensity of non-stoichiometric YAG increases with increasing antisite defects concentration, which is much stronger than that of the stoichiometric counterpart under the same conditions. It indicates that non-stoichiometric YAG with antisite defects YAl,16a might be used as a potential candidate for scintillator. [ABSTRACT FROM PUBLISHER]

Bi4Si3O12\!\!:\!Zn^{2+}(BSO\!:\!Zn) polycrystalline powders were successfully prepared by sol-gel method. X-ray diffraction measurements confirm that the Zn^2+-doped materials are all monophasic solid solution powders. The influences of doping concentration on the photoluminescence and radioluminescence characteristics have been investigated and discussed. The Zn^2+ doped material shows a better light yield than that of undoped material under X-ray excitation. The fluorescence decay time of the optimal material, excited by UV has been aslso measured. The results show that the Zn^2+ ion doping has a positive effect on the light yield of BSO. But the crystal growth and characterizations of BSO:Zn polycrystalline powders prepared deserve further investigations. [ABSTRACT FROM PUBLISHER]

In the present work, multiferroic (1\-x)\ \BiFeO3\-x (\CoFe2{\O}4) (x=0, 0.3, 0.5) nanocomposite thin films were prepared by sol-gel spin coating process. Structural, electrical and magnetic properties of nanocomposite thin films have been studied. X-ray diffraction study confirmed the co-existence of both perovskite \BiFeO3 (BFO) and spinel \CoFe2{\O}4 (CFO) phases. Atomic force microscopy shows CFO particles distributed in BFO matrix. These nanocomposite thin films exhibit both ferroelectric and ferromagnetic switching at room temperature. The magnetic and dielectric properties are improved by incorporation of CFO grains in matrix of BFO. The saturation magnetization (M_s) increases as x varies from 0 to 0.5. For x=0.5, M_s is found as high as \sim196~\emu/cm^3. Coercivity is increased with CFO concentration and found maximum (H_c\sim1.20~\kOe) for x=0.50. This large increase in coercivity indicates strong magnetoelastic coupling. The dielectric constant of the films is increased from 240 (for x=0) to 370 (for x=0.5). All composite films show ferroelectric behavior, however the ferroelectric properties are found to decrease with incorporation of magnetic phase. [ABSTRACT FROM PUBLISHER]

The role of \Bi2{\O}3 addition on the structural and magnetic properties of NiCuZn-Tb ferrites with composition \Ni0.5{\Cu}0.25{\Zn}0.25{\Tb}0.1{\Fe}1.9{\O}4+{\xBi}2{\O}3 has been investigated, where values of x (in wt %) are 0, 1, 2 and 3. Samples were prepared by the sol-gel auto combustion synthesis. The crystallographic, structural and magnetic properties of the samples were investigated by X-ray diffraction (XRD), scanning electron micrography, vibrating sample magnetometer and permeability measurements. Cubic spinel structure was observed from the XRD pattern for all the samples, implying that the \Bi2{\O}3 additives did not form a visible second phase in \leq 2 wt% of \Bi2{\O}3. Microstructural studies showed that \Bi2{\O}3 forms a liquid-like phase and promotes the grain growth. The average grain size increased for \leq 2 and then decreased for > 2 wt% of \Bi2{\O}3 content. The maximal grain size appears with 2 wt% \Bi2{\O}3. These characteristics evidently affect the magnetic properties, such as saturation magnetization (Ms) and permeability of the NiCuZn-Tb ferrites. \Bi2{\O}3 increase the Ms, bulk density (dB) and permeability effectively, while excessive \Bi2{\O}3 concentration results in the abnormal grain growth and decrease of Ms and dB. [ABSTRACT FROM PUBLISHER]

Nanoparticles of MnFe2O4 were synthesized via sol-gel method, with calcination processes at 400^\circC and 500^\circC in air. The effects of the different calcinations in the formation of the crystal structure and magnetic and optical properties were studied with X-ray diffraction (XRD), electron microscopy, SQUID magnetometer, and optical absorption. The XRD studies reveal the formation of a phase corresponding to cubic spinel structure in both samples and the presence of a second phase identified as Fe2O3, in the case of the sample with higher temperature treatment. The TEM images of the first sample show small nonuniform nanoparticles with a mean size of 7.8 nm, with a strong tendency to form agglomerates. Magnetization studies as a function of temperature were carried following field-cooled (FC)-Zero-field-cooled (ZFC) routines, where the ZFC curves exhibit blocking temperatures close to 250 K in both cases, and the behavior of the samples below this temperature suggests strong interaction between the particles. In the magnetization as a function of magnetic field studies, the curves display a tendency to saturate at low temperatures and the system shows superparamagnetic behavior above the blocking temperature. Saturation magnetization values (at low temperatures) are low compared to the expected ones, according to the Néel model of collinear spins, this can be attributed to canting effects or the presence of a second antiferromagnetic phase, specifically in the sample treated at 500^\circC. No significant differences were observed in the magnetic behavior of the samples. Semiconducting characteristics of the ferrites were confirmed by optical absorption measurements, obtaining an energy gap value close to 2.23 eV at room temperature. [ABSTRACT FROM PUBLISHER]

Electrical stress and 10-keV x-ray and 1.8-MeV proton irradiation and annealing responses are evaluated for graphene-based non-volatile memory devices. The memory characteristics of these structures derive primarily from hysteretic charge exchange between the graphene and interface and border traps, similar to the operation of metal-nitride-oxide-semiconductor memory devices. Excellent stability and memory retention are observed for ionizing radiation exposure or constant-voltage stress. Cycling of the memory state leads to a significant reduction in memory window. [ABSTRACT FROM AUTHOR]

Here we report our study on the lithium-doped ZnO films prepared by sol-gel method. The films are polycrystalline wurtzite structure and the average particle size is about 50 nm. All the films are ferromagnetic, and the film with Li content of 8 at. % has the largest saturation magnetization of about 55 memu/g. The photoluminescence spectra show that the films have weak emission near ultraviolet region and strong emission in visible regions. The Li atoms in Zn sites can induce Zn vacancies and a low acceptor level in the energy gap, which are required for ferromagnetism. The first-principles calculations demonstrate that the ferromagnetism in the Li-doped ZnO originates from the induced magnetic moment of oxygen atoms in the nearest neighbor sites to Li-Zn vacancy pair. [ABSTRACT FROM AUTHOR]

A high-current-density scandate tungsten dispenser cathode was used for the demonstration of a 25 : 1-aspect-ratio 750-\A/cm^2 -current-density sheet beam for the Defence Advanced Research Project Agency High-Frequency Integrated Vacuum Electronics (HiFIVE) program intended for the realization of a wideband (\sim30%) 220-GHz traveling wave tube. The elliptical cathode with homogeneous microstructure was made from 1–2-\mu\m-size tungsten powder added with nanosized Scandia using the sol-gel method; it has a current density of up to 160 \A/cm^2 at 1050 ^\circ\C. A sheet beam gun analyzer was built to test the terahertz sheet beam gun and determine the size and current density of a sheet electron beam produced by the impregnated scandate tungsten dispenser cathode. A sheet electron beam with an aspect ratio of 12.5 : 1 with a current density exceeding 375 \A/cm^2 has been obtained using a BVERI impregnated scandate dispenser cathode without magnetic compression; further magnetic field compression would give the final current density of 750 \A/cm^2. [ABSTRACT FROM PUBLISHER]

The effects of lithium (Li) doping on the performance of solution-processed zinc oxide (ZnO) thin-film transistors (TFTs) grown using the sol–gel method are investigated. Li-doped ZnO films as channel layers are chemically prepared by spin coating the gel with an aqueous solution of zinc acetate dihydrate, Li nitrate, and ethanolamine. TFT devices fabricated with 2 at.% Li-doped films show a good field-effect mobility of 3.31 \cm^2/\V\cdot \s, a subthreshold slope of 0.82 V/dec, and an on–off current ratio of over \10^5. These TFT devices also show good thermal and electrical stability, which is mainly attributed to the compact surface morphology of the channel layer, small carrier concentration, and less oxygen deficiency, which reduces the interface electrical trapping at the gate insulator. [ABSTRACT FROM AUTHOR]

In this study, an effort has been made to synthesize nano-scale barium titanate powder by sol-gel and hydrothermal methods. Characterization of the synthesized Barium Titanate is conducted by using X-ray diffraction for crystallite size, Transmission Electron Microscopy for particle size and scanning electron microscopy for surface morphology. It is observed that the powders prepared by Sol-gel and hydrothermal routes have almost similar average crystallite size of 34 ± 2 nm. Electrical properties such as dielectric constant, dielectric dissipation factor and electrical resistivity have also been measured. Hydrothermal process has enabled the synthesis of material with higher dielectric constant of 4000 compared to the Sol-gel route value of 1600. The dielectric dissipation factor is measured and found to be below 0.3 over a wide range of frequencies for powders generated using both processes. [ABSTRACT FROM AUTHOR]