Properties Of Fe2O3 Thin Films Research Articles

The role of a tantalum interlayer in enhancing the properties of Fe3O4 thin films.

High spin polarization and low resistivity of Fe3O4 at room temperature have been an appealing topic in spintronics with various promising applications. High-quality Fe3O4 thin films are a must to achieve the goals. In this report, Fe3O4 films on different substrates (SiO2/Si(100), MgO(100), and MgO/Ta/SiO2/Si(100)) were fabricated at room temperature with radio-frequency (RF) sputtering and annealed at 450 °C for 2 h. The morphological, structural, and magnetic properties of the deposited samples were characterized with atomic force microscopy, X-ray diffractometry, and vibrating sample magnetometry. The polycrystalline Fe3O4 film grown on MgO/Ta/SiO2/Si(100) presented very interesting morphology and structure characteristics. More importantly, changes in grain size and structure due to the effect of the MgO/Ta buffering layers have a strong impact on saturation magnetization and coercivity of Fe3O4 thin films compared to cases of no or just a single buffering layer.

Effect of different metallic doping elements on the physical properties of iron oxide thin films

This study investigates the physical properties of pure and Co, Cr, Mn, and Ni-doped Fe2O3 thin films fabricated using spray pyrolysis techniques on glass substrates. The primary aim is to understand how doping influences the structural, optical, and dielectric properties of Fe2O3 thin films. The deposition parameters were kept constant for all samples, with a fixed dopant concentration of 3 weight percent (wt%). X-ray diffraction (XRD) analysis revealed a single diffraction peak indexed as (104), decreasing in crystallite size from 17.27 nm for the pure film to approximately 11.5 nm for all doped films. Field emission scanning electron microscopy (FE-SEM) images displayed non-homogeneous grain formation, characterized by an average grain size larger than the crystallite size, indicating agglomeration. The optical band gap value shifted from 2.54 eV for the pure film to higher values upon doping with various elements, signifying direct allowed transitions. Changes in refractive index dispersion with wavelength were observed based on the dopant type. The application of the Spitzer-Fan model revealed an increase in high-frequency dielectric constant upon doping compared to the pure film, varying across different dopants. Photoluminescence (PL) spectra recorded under excitation at 340 nm exhibited multiple emission peaks within the spectral range of 399 to 600 nm.

Regulation of antiphase boundary density in Fe3O4 thin films and its effect on the electrical and magnetic properties

Antiphase boundaries (APBs) widely exist in Fe3O4 thin films and affect significantly their electrical and magnetic properties. Here, effects of APBs on the electrical and magnetic properties of Fe3O4 thin films have been quantitatively investigated by a combined study of pulsed laser deposition, transmission electron microscopy (TEM) and first-principles calculations. It was revealed that the substrates affected greatly the density of APBs in Fe3O4 thin films but did not change the atomic structures of APBs. The APB density in the Fe3O4 (111) thin film grown on the MgO (111) substrate was one order of magnitude larger than that on the Al2O3 (0001) substrate. Atomic-scale TEM characterizations revealed that the APBs in the Fe3O4 thin films on both substrates had three types of atomic structures. Due to the higher APB density in the Fe3O4/MgO thin film, the electrical resistivity at 300 K was two orders of magnitude larger than that of the Fe3O4/Al2O3 thin film. Meanwhile, the saturation magnetization and the coercivity of the Fe3O4/MgO thin film were reduced by 86 % and 35 %, respectively. First-principles calculations suggested that the antiferromagnetic coupling was easily formed at all the three types of APBs, which led to the decrease of spin polarization and the increase of electrical resistance of the Fe3O4 thin films.

Effect of Mg Doping on the Physical Properties of Fe2O3 Thin Films for Photocatalytic Devices.

Undoped and Mg-doped (y = [Mg2+]/[Fe3+] = 1, 2, 3, and 4 at.%) Fe2O3 thin films were synthesized by a simple spray pyrolysis technique. The thin films were extensively characterized. X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) analysis confirmed the successful insertion of Mg in the rhombohedral structure of Fe2O3. In addition, scanning electronic microscope (SEM) and confocal microscope (CM) images showed a homogenous texture of the film, which was free of defects. The rough surface of the film obtained by spray pyrolysis is an important feature for photocatalysis and gas sensor applications. The direct band gap of the doped Fe2O3 films obtained for [Mg2+]/[Fe3+] = 3 at.% was Edir = 2.20 eV, which recommends the Mg-doped iron oxide as an optical window or buffer layer in solar cell devices. The photodegradation performance of Mg-doped Fe2O3 was assessed by studying the removal of methylene blue (MB) under sunlight irradiation, with an effective removal efficiency of 90% within 180 min. The excellent photodegradation activity was attributed to the strong absorption of Mg-doped Fe2O3 in the UV and most of the visible light, and to the effective separation of photogenerated charge carriers.

Modulation on the magnetic and electrical properties of Fe3O4 thin films through strain relaxation

A series of Fe3O4 thin films with growth temperature ranging from 400 to 600 °C are prepared by magnetron sputtering on α-Al2O3 (0001). XRD and XPS measurements indicate that all the samples are pure Fe3O4 (111) epitaxial thin films. Microscopic strain is highly sensitive to the growth temperature. As a result, the magnetic and electrical measurements show some interesting phenomena related to the strain relaxation. The saturation magnetization demonstrates a monotonous increase in relative change as large as 85.9% originating from the strain relaxation effect. The improvement of magnetic anisotropy in Fe3O4 thin films is attributed to the reduction of strain-induced anisotropy. However, the resistivity changes suddenly at the growth temperature of 450 °C, which is dominated by mesoscopic grain size rather than microscopic strain.

First investigation on (Ni, Co) co-doping effects on the physical properties of Fe2O3 thin films for optoelectronic applications

A simple chemical spray pyrolysis technique was used to fabricate Ni and Co co-doped Fe2O3 thin films. All the co-doped layers are formed of α- Fe2O3 phase. The influence of the dual doping on the physical properties of the as deposited layers was investigated. The SEM and CM images revealed that co-doping changed the surface morphology of the Fe2O3 films. The main particle shape and size were significantly influenced by each dopant. The Optical measurement showed that the band gap varies in the range of [1.99–2.16] eV for direct transition and in the domain of [1.87–1.96] eV for indirect transition, it is affected by the dopant concentrations. The photocatalytic degradation of methylene blue dye under sunlight irradiation was investigated for all the grown layers. The obtained result showed high photocatalytic efficiency. The (Ni 2%, Co 1%) co-doped Fe2O3 thin films showed a degradation efficiency around 50 % after 2 h of sunlight irradiation.

Influence of Al doping on the structure and properties of Fe2O3 thin films: high transparency, wide band gap, ferromagnetic behavior

This paper presents a detailed study of structural, morphological, optical, transport and magnetic properties of aluminum (Al) doped ferric oxide (Fe2O3) thin films deposited onto glass substrates at 350 °C by spray pyrolysis technique. Al concentration was varied from 0 to 10 atomic percentages (at%). The x-ray diffraction patterns of Al doped Fe2O3 thin films showed the corundum structure with the predominant (104) peak. In scanning electron micrographs, the surfaces of the Al doped Fe2O3 thin films were observed to be formed of nanoparticles. Al doped Fe2O3 thin films were transparent in the visible to near infrared region. Transmittance and optical band gap of Al doped Fe2O3 thin films increased with the rise of Al concentration up to 6 at% and then decreased for the 8 and 10 at% Al concentrations. Al doped Fe2O3 thin films showed n-type electrical conductivity with high mobility and Hall coefficient. Electrical resistivity of Al doped Fe2O3 thin films varied from 5.67 × 105 to 8.92 × 105 Ω-cm and carrier concentration was found between 1.56 × 1017 and 8.64 × 1017 cm−3. Hysteresis loops of Al doped Fe2O3 thin films recorded at room temperature matched with the nature of soft ferromagnetic materials and the saturation magnetization decreased with Al concentration in Fe2O3 thin films.

Physical properties and Rietveld analysis of Fe2O3 thin films prepared by spray pyrolysis: Effect of precursor concentration

Iron oxide (Fe2O3) thin films have been prepared starting from iron chloride (FeCl3) precursor by spray pyrolytic decomposition of FeCl3 on an ordinary glass substrate at 450 °C. The precursor concentration (C) has been varied from 0.06 to 0.3 mol l−1 keeping the other deposition parameters fixed. The (C) effect on the structural, optical and electrical properties has been studied. The XRD analysis shows that Fe2O3 thin film has a rhomboedric structure with (104) plane as preferential orientation. A degradation of crystallinity followed by a change in plan orientation from (104) to (110) has been observed, when (C) has been raised to 0.2 mol.l−1.The optical transmittance spectrum shows that T(λ) decreases at higher precursor concentration. Optical band gaps w decreased from 2.21 to 2.08 eV for direct transition and from 2.03 to 1.99 eV for indirect transition when (C) increases from 0.06 to 0.3 mol l−1. The extinction coefficient (k) and refractive index (n) were also has been estimated and studied. The films deposited with C = 0.14 mol l−1 has shown the maximum mobility of 62 cm2 V−1.s−1 at room temperature. All physical properties of Fe2O3 thin films investigated in this work were strongly dependent upon the precursor concentration. The obtained results provide valuable information about structural, optical, photoluminescence and electrical properties of sprayed Fe2O3, which is a very helpful issue for better understanding and perfection of the semiconductor quality for the optoelectronic application.

Optical characteristics of iron oxide thin films prepared by spray pyrolysis technique at different substrate temperatures

The authors devoted this paper to study the influence of the substrate temperature upon optical characteristics of iron oxide thin films. Spray pyrolysis technique, SPT, was used to deposit Fe2O3 thin films onto preheated glass substrates (450 °C$$\geq$$ Tsub $$\geq$$ 250 °C). X-ray diffraction (XRD) revealed that the formed thin-film sample of Tsub 300 °C are hematite samples of polycrystalline nature and they have the rhombohedral structure. The optical properties of the present thin films were studied at room temperature in the wavelength range 300–2500 nm. Transmittance and reflectance measurements were utilized to determine and study the optical properties and optical constants. The absorption coefficient, optical density, the optical energy gap, Urbach energy, steepness parameter, and the electron–phonon interaction of films have been evaluated and discussed. The optical energy gap, Eg, was the result of direct and indirect allowed transitions. Eg increased from 2.10 eV to 2.39 eV when the transition is direct and from 1.87 eV to 1.99 eV for indirect transition. While Urbach’s energy decreased from 223 meV to 143 meV and the electron–phonon interaction from 4.089 to 1.778 when the substrate temperature was increased from 250 °C to 450 °C, respectively. The extinction coefficient and refractive index have been also estimated and studied. All optical properties of Fe2O3 thin films discussed in this research work have been strongly dependent upon the substrate temperature.

Particle size-band gap energy-catalytic properties relationship of PSE-CVD-derived Fe3O4 thin films

Abstract This study reports the control of catalytic properties of Fe3O4 thin films through adjusting the particles size and optical properties. Structure analysis of the obtained materials by X-ray diffraction indicated the formation of pure magnetite structure of Fe3O4. X-ray photoelectron spectroscopy showed that the surfaces of the samples were mainly composed of Fe2+, Fe3+, O2−, CO32− and OH−. Scanning electronic microscopy displayed a smooth films surface with an agglomerated crystallite grains. Both XRD and SEM exhibits particles size increases (∼40 to ∼60 nm) with the substrate temperature (Ts), while micro-strain in the sample decreased. The correlation of the Ts with optical energy band gaps (EgOpt) determined from UV visible (UV–vis) measurements indicated the increase of indirect (2.17 ≤ Eg2Opt≤ 2.25 eV) and direct (2.78 ≤ Eg1Opt≤ 2.95 eV) band gap of Fe3O4. Fe3O4 samples have been successfully tested towards the total oxidation of CO. While the change in EgOpt of Fe3O4 has been explained on the basis of the variation in the grain size and likely adsorbed oxygen (OAds) with Ts, the catalytic performance was suggested to be strongly dependent on the films microstructure, catalysts surface composition and more importantly with the EgOpt and OAds variation. Moreover, theoretical calculations based on DFT method of CO oxidation over Fe3O4 film surface catalyst demonstrated that OAds was the most involved oxygen species during the catalytic process, revealing that the LH mechanism is the most appropriate route for the CO catalytic oxidation over MvK and ER mechanisms. This approach of highlighting the interplay among the particle size, optical and catalytic properties with DFT calculations can pave the way to better understand the catalytic behavior of other transition metal oxides.

Optical Properties of Fe3O4 Thin Films Prepared from the Iron Sand by Spin Coating Method

Research on magnetic oxide is growing very rapidly. This magnetic oxide can be found in nature that is in iron sand. One of the beaches in Sumatera Barat containing iron sand is Tiram Beach, Padang Pariaman District, Sumatera Barat. The content of iron sand is generally in the form of magnetic minerals such as magnetite, hematite, and maghemit. Magnetite has superior properties that can be developed into thin films. The purpose of this research is to investigate the optical properties of transmittance, absorbance, reflectance and energy gap from Fe3O4 thin films. This type of research is an experimental research. The iron sand obtained from nature is first purified using a permanent magnet, then made in nanoparticle size using HEM-E3D with milling time for 30 hours. After that, the process of making thin film with sol-gel spin coating method. In this research, variation of rotation speed from spin coating is 1000 rpm, 2000 rpm and 3000 rpm. Based on XRD results indicated that the iron sand of Tiram beach contains magnetite minerals and the SEM results show that the thickness of the thin films formed is 25μm, 24μm and 11μm. The characterization tool used for characterizing optical properties is the UV-VIS Spectrophotometer. So it can be concluded that the greater the speed of rotation the thickness of the thin layer will be smaller, resulting in the transmittance and reflectance will be greater, while the absorbance will be smaller. Energy gap obtained from this research is 3,75eV, 3,75eV and 3,74eV. So the average energy gap obtained is 3,75eV.

The Effect of Thickness on the Physical Properties of Fe2O3 Thin Films Prepared by DC Magnetron Sputtering

The objective of this study is to assess the influence of nano-particle Fe2O3 thin film thickness on some physical properties which were prepared by magnetron DC- sputtering on glass substrate at room temperature. The structure was tested with X-Ray diffraction and it was to be amorphous and to become single crystal with recognized peak in (003) after annealing at temperature 500oC. The physical properties as a function of deposition parameters and then film thickness were studied. The optical properties such as absorbance, energy gap and some optical constants are measured and found that of about (3eV) energy gap.

Growth and optical properties of Fe2O3 thin films: A study of quantum confinement effects by experiment and theory

Thin iron films in the thickness range 0.7–48nm have been deposited on high quality Corning glass and Si(100) substrates by radio frequency magnetron sputtering. The films were then oxidized by annealing at temperatures of 400−450°C in a furnace in air. X-ray diffraction experiments revealed the formation of single-phase α-Fe2O3. The films were continuous and present negligible surface roughness. Ultraviolet-visible light absorption spectroscopy has shown a blue shift of both, the indirect and direct band gaps of hematite. The experimental results are interpreted as evidences of quantum confinement effects. This is facilitated by theoretical calculations based on Hartree Fock approximation as applied for an electron-hole system, in the framework of effective mass approximation. The agreement between theory and experiment supports the quantum confinement interpretation.

Large third-order optical nonlinearities in iron oxide thin films synthesized by reactive pulsed laser deposition

We report on a study of the third-order nonlinear optical properties of Fe2O3 thin films, grown by the method of laser deposition on silica (SiO2) substrates. The films were synthesized on substrates at different temperatures (293 K and 800 K) and under different oxygen pressures (0.1 Pa, 0.5 Pa, 1.0 Pa). The resulting films were amorphous, if grown on cold substrates (293 K), or polycrystalline otherwise. The third-order optical susceptibility χ(3) of the films was determined by the Z-scan method at the wavelengths of 1064 nm and 532 nm and the laser pulse width of 20 ns. Remarkably high χ(3) values on the order of 10−4 esu at 1064 nm are obtained. The results show that Fe2O3 thin films are promising nonlinear materials for contemporary optoelectronics.

Magnetic, transport, and magnetotransport properties of the textured Fe3O4 thin films reactively deposited onto SiO2/Si

The structural, magnetic, transport, and magnetotransport properties of Fe3O4 thin films with thicknesses from 38 nm to 95 nm are systematically investigated. The occurrence of the Verwey transition in these films at a temperature of about 120 K is established. It is found that the temperature dependences of the magnetic moment have a feature near 40 K, which can be attributed to the multiferroic phase. According to the X-ray diffraction data, the film structure represents a (001) texture. As was established using transmission electron microscopy, the height and width of texture crystallites increase with film thickness. Analysis of the temperature dependences of the resistivity showed that the dominant carrier transport mechanism in the films is thermoactivated tunneling. The thermoactivation energy, along with the room-temperature resistivity, decreases with increasing film thicknesses, which is most likely related to the variation in the crystallite size, especially in the crystallite width. The field dependence of magnetoresistance behaves similarly over the entire temperature range and has a positive MR peak in weak fields, which is related to spin-dependent tunneling through Fe3O4 grains and antiferromagnetically coupled antiphase boundaries.

Magnetic and transport properties of epitaxial Fe3O4 films grown at different oxygen pressure

The performance of spintronic devices depends critically on the ability to control the properties of high spin-polarization materials such as magnetite (Fe3O4) in thin films. In this work, the effect of oxygen pressure on the transport and magnetic properties of Fe3O4 thin films was extensively investigated. The 20 nm Fe3O4 films were grown on MgO (001) substrates using molecular beam epitaxy under different oxygen pressure. The quality of epitaxial Fe3O4 thin films was judged by observation of the Verwey transition and corroborated by x-ray photoemission spectroscopy (XPS). In particular, the resistivity measurements showed the Verwey transition to be as sharp as bulk magnetite, which has not been seen in previous studies for film thicknesses less than 30 nm. Therefore, this work provides insight for the growth of ultrathin magnetite films with high crystal quality and sharp Verwey transition. Furthermore, the magnitude of the magnetization change at the Verwey transition was observed to be sensitive to the oxygen pressure during film growth. These results are consistent with the XPS measurements and indicate a relative narrow range of optimal oxygen pressure for the formation of high quality thin magnetite films with electronic and magnetic properties close to bulk Fe3O4.

Effect of Annealing on Structural and Magnetic Properties of Magnetite Fe3O4 Thin Films Using Radio Frequency Magnetron Sputtering

This research work discusses the effect of magnetic annealing time on the structural and magnetic properties of magnetite thin films. Thin films were made using Radio Frequency Magnetron Sputtering technique in Argon atmosphere. The samples were then annealed magnetically at constant temperature of 3000C. The structural properties of Fe3O4 thin films were investigated using X-Ray Diffraction (XRD) while magnetic properties were studied using Vibrating Sample Magnetometer (VSM). The XRD results of these films confirmed the presence of the Fe3O4. Experimental results indicated the change of alignment of all the atoms of thin film parallel to the direction of applied field.

Growth temperature effect on the structural and magnetic properties of Fe3O4 films grown by the self-template method

We have investigated the effect of growth temperature on the structure, surface morphology, and magnetic properties of Fe3O4 thin films grown on SrTiO3(001) substrates by a self-template method. To eliminate the intermixing of (001) and (111) orientations that usually occurs in spinel films grown on perovskite substrates, a thin self-template layer of (001)-oriented Fe3O4 was deposited on a SrTiO3(001) substrate at 400 °C prior to the main film growth at temperatures of up to 1100 °C. Increasing the growth temperature from 400 °C to 1100 °C resulted in greatly improved crystallinity of the Fe3O4 thin films, with the rocking curve width dropping from 1.41° to 0.28°. Surface analysis by atomic force microscopy showed that raising the growth temperature increased the grain size and the surface roughness, ultimately leading to the formation of regular nanopyramid arrays at 1100 °C. The surface roughening and pyramid formation are caused by the dominance of the lowest surface energy spinel (111) crystal facet. The nanopyramids were fully relaxed but still perfectly (001)-oriented in the out-of-plane direction. The largest pyramids had the lowest coercivity due to a reduction of the demagnetization effect.

Photoelectrocatalytic activity of ferric oxide nanocatalyst: A synergestic effect of thickness

The Fe2O3 thin films have been deposited using ferric trichloride precursor at an optimized substrate temperature and concentration by simple chemical spray pyrolysis technique. Effect of quantity of the spraying solution on physicochemical properties of Fe2O3 thin films has been studied. Photoelectrochemical technique was used to optimize the quantity of a spraying solution. The PEC study shows that, Fe2O3 films are photoactive with relatively higher values of Isc=34.2μA and Voc=190mV respectively at 50ml quantity (thickness ~239nm). Effects of thickness on crystalline structure, morphology and optical properties have been studied. X-ray diffraction study confirms that the films are polycrystalline with rhombohedral crystal structure. The SEM and AFM micrographs depicts that the films are compact and needle shaped grains with grain size ~160–250nm. The direct band gap energy of Fe2O3 thin films is found to be in the range of 2.16–2.47eV. Four characteristic luminescence peaks having near band-edge, violet, blue and green emission are observed in the photoluminescence spectra. Photocatalytic degradation of benzoic acid by using Fe2O3 photoelectrode under visible light illumination has been investigated. The amount of mineralization is confirmed by COD and TOC analysis.

The structure, magnetic and transport properties of Fe3O4 thin films on different substrates by pulsed laser deposition

Magnetite thin films (10–300 nm) are deposited on different substrates including single crystals ((0001)-Al2O3, (001)-Si, (110)-SiO2), textured polycrystalline oxide underlayers (ZnO), amorphous glass, at temperature from room temperature to 550 °C by the pulsed laser deposition technique. Strong (111)-texture can be obtained on single crystal Si, SiO2, amorphous glass, and (0001)-textured ZnO layer, no matter whether they have either a huge lattice mismatch or no matching at all with Fe3O4. The film on single crystal Al2O3 (sapphire) shows a (111)-epitaxial structure with a strong in plane compressive strain. The saturated magnetization for magnetite thin films grown on SiO2 and Si substrates can reach 440 emu/cc while the epitaxial films grown on Al2O3 have a magnetization around 310 emu/cc when the film thickness is 40 nm. The substrate-induced strain in the films grown on Al2O3 substrates significantly affects the magnetic anisotropy and the magnetic coupling at the anti-phase boundaries in the films.