Fe-doped Films Research Articles

Electrodeposition of Fe-doped Sb2Se3 thin films for photoelectrochemical applications and study of the doping effects on their properties

Sb2Se3 (SSe) has been highlight as a low-cost, less complex, low toxicity, and earth-abundant photovoltaic (PV) absorber not only because of its excellent properties but also because of its demonstrated 5.6% certified efficiency and decent device stability. An understanding of the effects of intentional dopants on the properties of this material would help to further improve SSe PV devices. In this work, Fe-doped SSe thin film was obtained by electrodeposition at different levels of doping, which is an easy, cheap, and scalable technique. At the studied levels, this dopant caused low influence in band gap and morphologic-structural properties of the films; however, it did impact their electronic properties and photoactivity toward hydrogen gas evolution. The film obtained from a deposition bath composed of 5% of Fe presented a photocurrent similar to that shown by the undoped film, despite showing a carrier density that was three orders of magnitude higher. This behavior makes us believe that, compared to the undoped film, a photovoltaic device made with this 5% Fe-doped film would have a higher fill factor and efficiency.

Room Temperature Tunable Multiferroic Properties in Sol-Gel-Derived Nanocrystalline Sr(Ti1-xFex)O3-δ Thin Films.

Sr(Ti1−xFex)O3−δ (0 ≤ x ≤ 0.2) thin films were grown on Si(100) substrates with LaNiO3 buffer-layer by a sol-gel process. Influence of Fe substitution concentration on the structural, ferroelectric, and magnetic properties, as well as the leakage current behaviors of the Sr(Ti1−xFex)O3−δ thin films, were investigated by using the X-ray diffractometer (XRD), atomic force microscopy (AFM), the ferroelectric test system, and the vibrating sample magnetometer (VSM). After substituting a small amount of Ti ion with Fe, highly enhanced ferroelectric properties were obtained successfully in SrTi0.9Ti0.1O3−δ thin films, with a double remanent polarization (2Pr) of 1.56, 1.95, and 9.14 μC·cm−2, respectively, for the samples were annealed in air, oxygen, and nitrogen atmospheres. The leakage current densities of the Fe-doped SrTiO3 thin films are about 10−6–10−5 A·cm−2 at an applied electric field of 100 kV·cm−1, and the conduction mechanism of the thin film capacitors with various Fe concentrations has been analyzed. The ferromagnetic properties of the Sr(Ti1−xFex)O3−δ thin films have been investigated, which can be correlated to the mixed valence ions and the effects of the grain boundary. The present results revealed the multiferroic nature of the Sr(Ti1−xFex)O3−δ thin films. The effect of the annealing environment on the room temperature magnetic and ferroelectric properties of Sr(Ti0.9Fe0.1)O3−δ thin films were also discussed in detail.

Diffuse phase transition of sol-gel deposited BaFexTi2-xO5 thin films

BaFexTi2-xO5 (x = 0, 0.004, 0.008, 0.012) thin films were prepared on Pt/Ti/SiO2/(100)Si substrates via sol-gel process. The phase transition behavior of the BaTi2O5 thin film was investigated using temperature dependent dielectric measurements in conjunction with temperature dependent Raman spectra. Diffuse phase transition was found in BaTi2O5 thin film which exhibited a broad peak without frequency dependence on the ε versus T, ε(T), curves around 370 °C. As the Fe content increased, a broad near-plateau dielectric permittivity maximum occurred in a wide temperature range. For x = 0.012, the value of the broad permittivity maximum was 875 at 100 kHz in the temperature range of 150–300 °C. It means that the Fe-doped BaTi2O5 thin films exhibited enhanced diffuse phase transition behavior. The wide temperature stability of dielectric permittivity was obtained in the Fe-doped BaTi2O5 thin films, which are promising in the high-temperature application.

Influence of Fe-doping on the structural, optical and luminescent behavior of ZnO thin films deposited by spin coating technique

The current work describes the fabrication of Fe-doped zinc oxide thin films on a glass substrate using sol-gel spin coating technique. The undoped and Fe-doped ZnO films were annealed at the 400 °C for 3 h. The structural, optical, morphological and luminescent features were explored by using X-ray diffraction (XRD), diffuse reflectance, scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy techniques. It was noted that XRD patterns showed the polycrystalline nature and demonstrated a hexagonal wurtzite structure of Zn1-xFexO. With the rise in Fe ratio, the grain sizes of the deposited films start to cut as revealed from the SEM images. Interestingly, no variation has been noted in the transmittance value in the visible region. However, a lessening in the band-gap energy with an increment in the Fe concentration has been seen. PL curves exhibit ultraviolet emission peaks at 398 and 485 nm that are associated with the near band edge emission (NBE) and defect emission peak. It has been noted that the NBE emission shifts to longer energy with the rise in the Fe ratio. These results demonstrated the applicability of ZnO thin films as a suitable material for light emitting applications.

Synthesis and characterization of pure and Fe doped TiO2 thin films for antimicrobial activity

Pure and Fe-doped titanium dioxide sol-gel thin films were prepared by spin coating process. Pure and Fe-TiO2 films, containing 3–6% Fe, were annealed at 450 °C for 1h. All thin films were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–vis spectroscopy. From XRD data, the dominant crystalline phase of titanium dioxide was anatase, and the range of the crystal size for the films was 19–26nm. On the other hand, antibacterial activity of pure and Fe-doped titanium dioxide against E. coli and S. aureus was evaluated by international recognized test (JIS Z 2801). The test shows incrementally increasing in antibacterial activity of the thin films when dopant ratio increased under UV light.

Microstructure, magnetic and magneto-optical properties of Fe-doped SmCo5 thin films

The SmCo/Cu, SmCo/Cu/Cr and Fe-doped SmCo films on glass and Si (100) substrates are synthesized by pulsed laser deposition (PLD) technique. The microstructure, magnetism and magneto-optical Kerr effect (MOKE) of Fe-doped SmCo films are studied systematically. The results show that the corcivity and saturation magnetization of films deposited on Si substrates are better than that of on glass subatrates. It is also found that the surface morphology and magnetic properties of Fe:SmCo films are influenced by the annealing temperature. Meanwhile, the X-ray diffraction peaks of SmCo5 phase are enhanced, especially for SmCo5 (001), (002) and (003) peaks after annealing due to the enhancement of Cu (111) peak in the films with Cu buffer layer. Moreover, the MOKE of the samples on both glass and Si substrates are enhanced after Fe doping and the MOKE of samples is controlled by the Fe content, which provides a new way for optimizing the property of SmCo film as the magneto optical storages.

Combinatorial synthesis and high-throughput characterization of structural and photoelectrochemical properties of Fe:WO3 nanostructured libraries

Porous and photoelectrochemically active Fe-doped WO3 nanostructures were obtained by a combinatorial dealloying method. Two types of precursor materials libraries, exhibiting dense and nano-columnar morphology were fabricated by using two distinct magnetron sputter deposition geometries. Both libraries were subjected to combinatorial dealloying enabling preparation and screening of a large quantity of compositions having different nanostructures. This approach allows identifying materials with interesting photoelectrochemical characteristics. The dealloying process selectively dissolved Fe from the composition gradient precursor W–Fe materials library, resulting in formation of monoclinic single crystalline nanoblade-like structures over the entire surface. Photoelectrochemical properties of nanostructured Fe:WO3 films were found to be composition-dependent. The measurement region doped with ∼1.7 at % Fe and a film thickness of ∼ 900–1100 nm displayed highly porous WO3 nanostructures and exhibited the highest photocurrent density of ∼ 72 μA cm−2. This enhanced photocurrent density is attributed to the decreased bandgap values, suppressed recombination of electron–hole pairs, improved light absorption as well as efficient charge transport in the highly porous Fe-doped film with single crystalline WO3 nanoblades.

Resistive states in strontium titanate thin films: Bias effects and mechanisms at high and low temperature

A study on charge transport properties of thin film Fe-doped SrTiO3 epitaxially grown on Nb-doped SrTiO3 is reported. Electric measurements between 350 °C and 750 °C show a transition from predominant ionic to electronic conduction and lower conductivity of the thin films compared to the bulk of polycrystalline samples. Defect chemical changes at elevated temperature were investigated by applying a bias voltage. A model is described which successfully predicts additional features such as inductive loops or extra semicircles measureable by impedance spectroscopy as well as the complicated time dependence of electric DC-measurements. With this model it is also possible to calculate the negligibly small ionic conductivity next to the dominating electronic conductivity in the high temperature regime. The ionic conductivity is referenced by oxygen isotope depth profiling. Changes of resistive states in Fe-doped SrTiO3 thin films at high temperature and moderate fields are compared to room temperature resistive switching phenomena at high electric fields. A conductive filament based switching process is observed at room temperature, and the capability for forming such filaments and their electric properties is further analysed using microelectrodes.

Structure and magnetism of Fe-doped BaSnO3 thin films

BaSnO3 is an excellent candidate system for developing a new class of perovskite-based dilute magnetic semiconductors. In this study, we show that BaSn0.95Fe0.05O3 can be grown from a background pressure of ∼2×10−3 mTorr to oxygen pressures of 300 mTorr with high crystallinity and excellent structural quality. When grown in vacuum, the films may be weakly ferromagnetic with a nonzero x-ray magnetic circular dichroism signal on the Fe L3 edge. Growth with oxygen flow appears to suppress magnetic ordering. Even for very thick films grown in 100 mTorr O2, the films are paramagnetic. The existence of ferromagnetism in vacuum-grown BaSnO3 may be attributed to the F-center exchange mechanism, which relies on the presence of oxygen vacancies to facilitate the ferromagnetism. However, other possible extrinsic contributions to the magnetic ordering, such as clusters of Fe3O4 and FeO or contamination can also explain the observed behavior.

Study of Magnetic Properties of Fe-Doped CuO: Monte Carlo Simulations

Using Monte Carlo simulations, we are studying the magnetic properties of Fe-doped CuO thin films. The total magnetizations and the susceptibilities are studied as a function of the effect doping, external magnetic field, and exchange coupling. The critical temperature is discussed as a function of the effect of iron concentration. On the other hand, we investigate the effect of increasing temperatures on the coercive field for a constant value of exchange coupling and a fixed concentration. The coercive magnetic field is found to decrease with increasing temperature values until reaching its null value. The effect of increasing the exchange coupling amount on the saturation magnetic field H s is illustrated. A linear growth of the saturation magnetic field is found as a function of the exchange coupling interaction. To complete this study, we presented and discussed the magnetic hysteresis cycle loops.

Optical and magnetic properties of PbS thin films doped with Fe2+ ions

PbS and Fe-doped PbS thin films were deposited on glass substrates by spray technique using perfume atomizer. Fe concentration is varied as 0, 1, 2, 3 and 4wt.% and the effect of Fe doping concentration on the structural, morphological, optical, photoluminescence and magnetic properties of the PbS thin films are studied and the results obtained are discussed in this paper. Structural studies show that all the films have face-centered cubic crystal structure with a strong (2 0 0) preferential orientation. Crystallite size estimated from the Scherrer formula decreased from 55.73nm to 31.97nm with Fe doping. Elemental analysis confirmed that the undoped and doped PbS thin films are deficient with sulfur and the presence of emission peak at 485nm in the photoluminescence spectra strongly supports this. Optical band gap is blue shifted with Fe doping. Improved magnetic properties were observed for the doped PbS thin films. The obtained results infer that Fe2+ ions strongly enhanced the optical and magnetic properties of pure PbS thin films.

Conducting mechanisms and magnetic behaviours of Fe-doped In2O3 nanocrystalline films

The relation between conducting mechanism and magnetic behaviour of Fe-doped In2O3 thin films was investigated. The films were prepared by sol gel method followed by spin coating techniques and characterized by X-rays diffractions, field emission electron microscopy, transmission electron microscopy, Hall Effect at room and low temperature, X-ray photoelectron spectroscopy and vibrating sample magnetometer. Films’ lattice parameter decreased with increasing of Fe content. Average grain size of films ranged between 8.4 and 13nm. Oxygen vacancies of films tended to reduce with increasing of Fe doping. Films with x=0.025 and 0.05 showed typical semiconducting behaviour while transition from metallic- to semiconducting-like behaviour was observed at 190K and 230K for films with x=0.075 and x=0.15, respectively. No trend had been found between films saturation magnetization, Ms, and free charge carriers. The magnetic behaviour of films has a correlation with localized electrons of Nearest-Neighbour Hopping conduction.

Local structure and magnetic properties of Fe-doped SnO2 films

Sn1-xFexO2 (x = 0, 0.023, 0.042 and 0.075) films were prepared by radio frequency magnetron sputtering. X-ray diffraction shows that Fe doping does not alter the tetragonal rutile structure of SnO2. X-ray absorption fine structure (XAFS) characterization shows that no Fe metal clusters or secondary phases are formed and that Fe2+ and Fe3+ coexist and substitute the Sn sites with oxygen vacancies to compensate charge nonequilibrium in the Fe-doped SnO2 films. Fe 2p and asymmetric O 1s XPS spectra further verify the existence of Fe2+/Fe3+, lattice oxygen (SnO band) and anionic vacancies. The room temperature ferromagnetism of the films has a strong dependence on Fe-doping level. The saturation magnetization increases with increasing the Fe doping level, whereas the carrier concentration decrease. Which implies that the ferromagnetism is not mediated by carriers. The bound magnetic polarons resulted from the oxygen vacancies play a key role in the observed room temperature ferromagnetism.

Investigation of the structural, optical and magnetic properties of Fe doped ZnO thin films coated on glass by sol-gel spin coating method

Fe doped ZnO thin films with varying Fe concentrations say 0, 3, 5, 7, 10, 15, and 20 at% were prepared on the glass substrate by sol-gel spin coating technique and their structural, morphological, optical and magnetic properties were investigated. XRD results indicated that the prepared samples were single crystalline films with hexagonal wurtzite structure. Secondary phases or impurity clusters were not observed for the samples. SEM images of the prepared samples showed clear fibrous structures. AFM analysis revealed the increase of film roughness for the Fe doped films. Tauc's plot was used to find the band gap of the prepared samples which was found to increase with the increase of Fe concentration and thus showed a redshift. PL spectra showed NBE, violet, blue and green emissions for the undoped and Fe doped films. Magnetic measurements confirmed a clear ferromagnetic behavior for all the prepared samples.

Synthesizing nanostructured crack-free thick films of Fe-doped lead zirconate titanate by sol–gel dip coating method

Lead zirconate titanate is one of the most well-known ferroelectric oxides and has been widely used in nano/micro-electromechanical systems and piezoelectric industries. Doping the lead zirconate titanate thick films by Fe3+ as an acceptor dopant leads to hard lead zirconate titanate piezoelectrics for specific applications including high frequency transducers. In this article, Fe-doped lead zirconate titanate thick films with the thickness of 27 µm are synthesized by using a modified acetic acid/alcoholic based sol–gel method and applying diethanolamine as a complexing agent. Crystallographic measurements are performed considering lattice constants and lattice distortion of the films by means of X-ray diffraction. Pure perovskite phase is obtained by adding the dopant up to 5 at. % Fe. The tetragonal lattice distortion and lattice parameters decrease by adding Fe and reach to its minimum level of c t = 4.024 A and a t = 3.966 A at 3 at. % Fe. The surface morphology and grain size are surveyed using field emission scanning electron microscopy, which shows the reduction in grain size by adding the dopant. Polarization-voltage loops and dielectric constants of the films are calculated by electrical measurement and illustrate reduction in the polarization by increasing Fe dopant. The highest value of coercive voltage is achieved at 3 at. % Fe. Moreover, the lowest dielectric constant of 318 is obtained at 5 at. % Fe. Nanostructured crack-free Fe-doped PZT thick films are successfully prepared by using modified sol–gel route with different Fe dopant percentages (a) surface morphology of PF(3 %)ZT, (b) cross section of PZT thick film.

Effect of Fe doping on the magnetic properties of PbPdO2 nanograin film fabricated by sol-gel method

The single-phase Fe-doped PbPdO2 film was prepared using a sol-gel spin-coating method. The film had a nanograin structure consisting of compacted particles with an average crystallization size of about 35.2nm. Large amount of Pb vacancies were found in the film. The valences of the Pb, Pd and Fe ions of the film were confirmed to be near 2+, 2+ and 3+, respectively. The additional electron provided by Fe3+ and the high ionization energy of Fe3+ ensure the stability of the valence of doped Fe ions. The measurement of hysteresis loops and the theoretical fitting of the zero-field-cooled and field-cooled magnetization versus temperature curve indicated that the ferromagnetism and the paramagnetism coexist in the Fe-doped PbPdO2. And the ferromagnetism persisted up to 380K. A bound magnetic polaron model based on the Pb vacancies, the carriers and the doped Fe ions was utilized to account for the origin of the film's ferromagnetism. The isolated Fe ions or magnetic polarons were believed to be responsible for the paramagnetism in the film.

Optical properties of Fe-doped BaTiO3 films deposited on quartz substrates by sol-gel method

Fe-doped BaTiO3 films were prepared on quartz substrates by sol-gel route. Linearly optical constants of the films were obtained by fitting transmittance spectra with Adachi’s model. With increasing Fe composition, refractive index n at 532 nm increases, single oscillator energy Ec and dispersion energy Ed increase, but optical band gap Eg decreases from 3.78 to 3.63 eV. In addition, nonlinear optical properties of the Fe-doped BaTiO3 films were analyzed by Z-scan method. Nonlinear optical responses of the BaTiO3 films were enhanced by Fe doping. For BaTi0.96Fe0.04O3 film, the third-order nonlinear refractive index coefficient γ, the nonlinear refractive index coefficient n2, the nonlinear absorption coefficient β and the third-order nonlinear susceptibility χ(3) are 1.98 × 10−13 m2/W, 1.03 × 10−6 esu, 1.33 × 10−7 m/W, 2.38 × 10−7 esu respectively. The nonlinearity is predominated by the nonlinear refractive behavior. These results suggest that Fe doping may tune the linear and nonlinear optical properties of BaTiO3 films, which indicates that Fe-doped BaTiO3 films are promising materials for applications in optical devices.

Iron, nitrogen and silicon doped diamond like carbon (DLC) thin films: A comparative study

The X-ray absorption near edge structure (XANES), X-ray photoelectron spectroscopy (XPS), valence band photoemission (VB-PES) and Raman spectroscopy results show that the incorporation of nitrogen in pulsed laser deposited diamond like carbon (DLC) thin films, reverts the sp3 network to sp2 as evidenced by an increase of the sp2 cluster and ID/IG ratio in C K-edge XANES and Raman spectra respectively which reduces the hardness/Young's modulus into the film network. Si-doped DLC film deposited in a plasma enhanced chemical vapour deposition process reduces the sp2 cluster and ID/IG ratio that causes the decrease of hardness/Young's modulus of the film structure. The Fe-doped DLC films deposited by dip coating technique increase the hardness/Young's modulus with an increase of sp3-content in DLC film structure.

Photocatalytic Treatment of Desalination Concentrate Using Optical Fibers Coated With Nanostructured Thin Films: Impact of Water Chemistry and Seasonal Climate Variations.

Treatment of desalination concentrate can reduce concentrate volume for disposal, increase water recovery and convert waste to resource. However, concentrate treatment is costly and energy intensive due to high concentrations of salt and recalcitrant organic matter in concentrate. Photocatalytic oxidation provides a novel energy neutral technology for concentrate treatment by degrading organic contaminants. Polymer-assisted hydrothermal deposition method was used to synthesize innovative pure and Fe-doped TiO2 mixed-phase nanocomposite thin films on side-glowing optical fibers (SOFs). The properties of the photocatalysts-coated SOF were characterized by surface morphology, nanostructure, crystallite size and phase and zeta potential. Photodegradation efficiency and durability of the photocatalysts treating different types of desalination concentrate was studied under natural sunlight. Synthetic solutions and reverse osmosis (RO) concentrates from brackish water and municipal wastewater desalination facilities were tested to elucidate the impact of water chemistry, operating conditions and seasonal climate variations (solar irradiation intensity and temperature) on photocatalytic efficiency. High ionic strength and divalent electrolyte ions in RO concentrate accelerated photocatalytic process, whereas the presence of carbonate species and organic matter hindered photodegradation. Outdoor testing of immobilized continuous-flow photoreactors suggested that the catalyst-coated SOFs can utilize a wide spectrum ofnatural sunlight and achieved durable photocatalytic performance.

Effect of iron doping on the structural and optical properties of CeO2 films

Undoped and Fe-doped CeO2 thin films were fabricated by spin coating on F-doped tin oxide glass substrates followed by annealing at 500 °C for 15 h. The concentration of the dopant was varied from 2 to 10 % iron by weight (metal basic). Glancing angle X-ray diffraction and laser Raman microspectroscopy indicated that the films consisted only of CeO2 without any impurity phases of FexOy. The thickness of the films was determined by dual-beam focused ion beam milling to be ~150 nm for undoped film, while Fe-doped CeO2 films have thickness of ~200 nm for all dopant samples. The transmission spectra from UV–visible spectrophotometry showed a redshift of the absorption edge of the doped films, and the optical indirect band gap of the films decreased from 3.48 to 3.20 eV with increasing dopant concentration. Furthermore, the results have been proposed in the diagram of electron–hole trapping.