Pulsed Laser Deposition Technique Research Articles

Optical and Structural Analysis of TiO2-SiO2 Nanocomposite Thin Films Fabricated via Pulsed Laser Deposition Technique.

TiO2-SiO2 nanocomposite thin films have gained the attention of the scientific community due to their unique physical and chemical properties. In this paper, we report on the fabrication and characterization of a TiO2-SiO2 nanocomposite disk-shaped target. The target was used for the deposition of TiO2-SiO2 nanocomposite thin films on fluorine-doped tin oxide/glass substrates using the pulsed laser deposition (PLD) technique. The thicknesses of the thin films were fixed to 100 nm, and the deposition temperature ranged from room temperature to 300 °C. As revealed by the microstructural and morphological characterizations revealed, the TiO2-SiO2 nanocomposite thin films are amorphous and display homogeneous distribution. The determined values of the indirect optical band gap range from 2.92 to 3.07 eV, while those of the direct optical band gap lie between 3.50 and 3.55 eV. Additionally, as the deposition temperature decreases, the light transmission increases in the visible and in the ultraviolet ranges, which is suitable for flexible perovskite solar cells. This research can uncover new insights into the fabrication of amorphous TiO2-SiO2-based nanostructured thin films using the PLD technique for perovskite solar cell technology.

Effect of thickness on the superconducting properties of the thin films of FeTe0.55Se0.45 deposited on YSZ substrates using Pulsed laser deposition (PLD) technique

We report the successful fabrication of thin films of thickness ∼26 nm, 59 nm, 76 nm, and 158 nm of the composition FeTe0.55Se0.45 on the (100)-oriented Yttria-stabilized zirconia (YSZ) substrate using the pulsed laser deposition (PLD) technique. The effect of thickness on the structure and superconducting properties of the thin films has been investigated. X-ray diffraction study reveals the growth of thin films along the c-axis. The temperature-dependent resistivity measurements confirm superconductivity in all the fabricated thin films, and the highest ∼ 16.2 K has been observed for the thin film of thickness ∼59 nm, which is higher than the corresponding value of the polycrystalline target sample. The superconducting parameters such as upper critical magnetic field coherence length thermally activated energy (TAE) U0, and vortex phase state have been measured by magnetotransport measurements near in the different applied magnetic fields up to 12 T. The TAE values determined from the conventional and modified thermally activated flux flow (TAFF) models are discussed and compared. A crossover from 2-dimensional (2D) vortex to 3-dimensional (3D) vortex behaviour has been observed. The vortex phase diagrams are used to observe the transition from the vortex liquid to the vortex glass state in the grown thin films. Moreover, magnetoresistance (MR) measurements show non-saturating linear magnetoresistance (LMR) in the high field region, indicating the presence of the possible topological state in the grown thin films. The values of magnetic field dependent transport critical current density, have been evaluated from the current-voltage (I-V) curves. Furthermore, the normalised pinning force density has been used to characterize the pinning processes using the Dew Hughes’ scaling rule which reveals that the grown thin films contain δl-surface pinning centers.

Enhanced visible and IR light-sensing performance of photoconductive VO2 (M1) nanorods thin film

In this article, we report on the enhanced photo-response of VO2 (M1) nanorods (NRs) thin film upon exposure to visible and near Infrared (NIR) light. The growth of photoconductive VO2 (M1) NRs thin film has been carried out using a pulsed laser deposition (PLD) technique. Field emission scanning electron microscopy (FESEM) showed the formation of NRs-like structures on the deposited thin film. The semiconductor-to-metal transition (SMT) properties at ∼64.8 °C and ∼59.8 °C during the heating and cooling cycle respectively confirm the deposition of VO2 (M1) thin film. The formation of VO2 (M1) thin film is also validated by Raman spectroscopy and X-ray diffraction (XRD) techniques. The photoconductivity of the pulsed laser deposited VO2 (M1) NRs thin film has been studied using the simple planar geometry upon exposure to the visible light (650 nm) and NIR light (980 nm) at 2 V and 5 V bias voltages. The estimated rise time and fall time of the photoconductive VO2 (M1) NRs thin films were about 1.88 ms and 1.9 ms upon exposure to the visible light and 1.89 and 2.4 ms upon exposure to the NIR light respectively. The photo-responsivity values of ∼1120 mA/W and ∼138 mA/W have been achieved for the visible and NIR light respectively at 5 V bias voltage. The photoconductive VO2 (M1) NRs thin film reveals highly responsive and fast visible and NIR light-sensing performance with simple planar geometry (Ag/ VO2 (M1) NRs thin film/Ag).

A Comparison Study the Effect of Doping by Ga2O3 and CeO2 On the Structural and Optical Properties of SnO2 Thin Films

This research deals with the effect of gallium oxide and cerium oxide as dopants on the structural and optical characteristics of tin oxide. Gallium and cerium oxide doped tin oxide was prepared with different doping concentrations (0, 0.03, 0.05 and 0.07) wt. pure and doped tin oxide thin films were prepared by the pulsed laser deposition technique. X-ray diffraction and UV-Visible spectrophotometer were employed to investigate both oxides doping effects. Results showed that all prepared samples have poly-crystalline structure with a preferred plane of crystal growth along (110), where the crystal size grew from 40.3 nm to 64.5 nm and to 43.5 nm for Ga2O3 and CeO2 doped tin oxide thin films, respectively. Transmittance decreased drastically by increasing the doping ratio of gallium oxide. In contrast, it increased by increasing the doping ratio of cerium oxide. The optical energy gap was found to change in nonsystematic sequence with the increase of Ga2O3 doping concentration, while it decreased monotonically by increasing the CeO2 doping concentration.

Hydroxyapatite Thin Films of Marine Origin as Sustainable Candidates for Dental Implants.

Novel biomaterials with promising bone regeneration potential, derived from rich, renewable, and cheap sources, are reported. Thus, thin films were synthesized from marine-derived (i.e., from fish bones and seashells) hydroxyapatite (MdHA) by pulsed laser deposition (PLD) technique. Besides the physical-chemical and mechanical investigations, the deposited thin films were also evaluated in vitro using dedicated cytocompatibility and antimicrobial assays. The morphological examination of MdHA films revealed the fabrication of rough surfaces, which were shown to favor good cell adhesion, and furthermore could foster the in-situ anchorage of implants. The strong hydrophilic behavior of the thin films was evidenced by contact angle (CA) measurements, with values in the range of 15-18°. The inferred bonding strength adherence values were superior (i.e., ~49 MPa) to the threshold established by ISO regulation for high-load implant coatings. After immersion in biological fluids, the growth of an apatite-based layer was noted, which indicated the good mineralization capacity of the MdHA films. All PLD films exhibited low cytotoxicity on osteoblast, fibroblast, and epithelial cells. Moreover, a persistent protective effect against bacterial and fungal colonization (i.e., 1- to 3-log reduction of E. coli, E. faecalis, and C. albicans growth) was demonstrated after 48 h of incubation, with respect to the Ti control. The good cytocompatibility and effective antimicrobial activity, along with the reduced fabrication costs from sustainable sources (available in large quantities), should, therefore, recommend the MdHA materials proposed herein as innovative and viable solutions for the development of novel coatings for metallic dental implants.

Terahertz emission enhancement of GaAs-based photoconductive antennas via the nanodecoration of their surface by means of pulsed-laser-deposition of gold nanoparticles

We report a systematic study of free-space terahertz (THz) emission from photoconductive antennas (PCAs) nanodecorated with gold nanoparticles (Au-NPs) deposited by using the pulsed laser deposition (PLD) technique. H-shaped dipole micro-structured PCAs fabricated on semi-insulating GaAs substrates were decorated under various PLD conditions. Thus, by increasing the number of laser ablation pulses (NLP) of the Au target, both the average size of Au-NPs and the surface loading of PCAs increase. Compared with non-decorated PCAs, those decorated with Au-NPs exhibit significant enhancement in the radiated THz pulse amplitude. A maximum enhancement of ∼2.3 was achieved at NLP = 1250. Under this optimal NLP condition, not only is the average Au-NP size (of ∼15 nm) favorable for light absorption via localized surface plasmons, but also the inter-distance between NPs, the light reflectance, and facilitated transport of photocarriers, all combine to yield a stronger THz field emission. For higher NLP (≥2000), NPs coalesce and tend to form continuous film NPs, which not only significantly limits the light scattering toward the GaAs underlying substrate, but also electrically shorts the PCA. Finally, the Au-NP decoration of GaAs PCAs was also found to improve their overall thermal conductivity, making them much more thermally stable than their non-decorated counterparts.

Growth and Characterizations of Superconducting FeSe Films on Flexible F-Mica Substrates

This work first reports the preparation of superconducting FeSe films on fluorophlogopite-mica (F-mica) substrates by pulsed laser deposition (PLD) technique. The quality of films is significantly improved by optimizing the deposition conditions, such as substrate temperature and laser energy. Through mechanical exfoliation of F-mica substrates, the films obtain excellent flexibility. After repeated bending in the atmosphere, the surface morphology and superconducting properties of these films substantially remain unchanged. Furthermore, we use a homemade device to apply different stains to the film and conclude that the superconducting transition temperature could be enhanced under compressive strain, whereas reduced under tensile strain. This paper shows the great potential of FeSe superconducting films to integrate with future flexible electronic devices.

Impact of substrate -target distance on the hemispherical expansion plume generated by the deposit of SnSe nanoparticle thin films

The pulsed laser deposition technique utilised to deposit SnSe thin films on quartz substrates utilises Nd:YAG laser at the temperature of 573 ​K with different substrate–target distances (Ds-t) of 2, 2.5, 3 and 3.5 ​cm. X-ray diffraction of the thin films revealed an orthorhombic phase with a polycrystalline structure. Crystallite size decreased when Ds-t increased. Field emission scanning electron microscopy showed the film morphology and revealed the formation of spherical and nanorod structures with increasing Ds-t. The energy band gap calculated from transmittance data increased in the range of 1.71–3.65 ​eV with increasing Ds-t. The absorption coefficient, refractive index, loss factor (loss tangent), extinction coefficient and optical conductivity were affected by Ds-t variation.

Ordered LiFe5O8 thin films prepared by pulsed laser deposition as an anode material for all-solid thin film batteries

The search for obtaining a Co free low-cost and high-capacity anode thin film material for high energy density all-solid thin film batteries has been driving the increasing innovation and research in Li-ion battery (LIB) technology. In the present case, LiFe5O8 (LFO) thin films are prepared by pulsed laser deposition (PLD) technique and their electrochemical properties, Li ion dynamics, conducting processes at various frequencies and current rates are explored. LFO thin films are seen to crystallize in ordered α -phase with an inverse spinel structure. Chemical state of all the elements is analysed using X-ray photoelectron spectroscopy method. Cyclic voltammeter (CV) study carried out between 0–3 V shows the reduction peak at 0.76 V initially and in the later cycles at 0.86 V with a small shift depicting the exact conversion type behaviour of the LFO thin film. LFO thin film exhibits specific discharge capacity of 25 μAh/cm2 at 10 μA/cm2 current density during the first cycle. Rate capability measurements are carried out at various current densities of 10, 20, 30, 40, 50 and 10 μA/cm2. Li-ion diffusion coefficient during the de-lithiation and lithiation process is seen to be 3.78 × 10−14 cm2/s and 1.41 × 10−13 cm2/s, respectively. CV studies at various scan rates indicates that the mechanism of Li+ storage is dominated by a diffusion-controlled process at low scan rates and with increasing scan rate it becomes a surface-controlled process. Electrochemical impedance studies at various frequencies shows the decrease in charge transfer resistance with increasing cycles. Combined structural, chemical, electrochemical and impedance studies of LFO thin films indicates that these films can be employed for fabricating Co and Ni free all-solid thin film Li-ion batteries for energy storage applications.

Laser ablated uniform deposition of bismuth oxide film as efficient anode for zinc based flow battery

Zinc based redox flow batteries are the most proficient and attractive candidature for large scale energy storage applications. However, zinc dendritic formation and inhomogeneous deposition of zinc hamper the cyclability of zinc-based flow batteries. Herein, we have successfully decorated Bi2O3 on the felt by using the pulsed laser deposition (PLD) technique and tested it as a negative electrode in zinc bromine redox flow battery. The Bi2O3 felt provides more robust nucleation sites for zinc nuclei, lowers the potential of hydrogen evolution reaction, minimizes the surface diffusion of zinc, lowers zinc nucleation overpotential, and triggers homogenous zinc deposits. Compared to pristine (57.7 %), Bi2O3 felt exhibited an energy efficiency of 70.6 % at 100 mA cm−2. Interestingly, the morphological evolution of zinc deposits demonstrates that zinc deposition on the Bi2O3 felt is more homogeneous than pristine at an initial time (30 sec of charging at 20 mA cm−2). Moreover, Bi2O3 felt shows a stable long cycling performance over 200 cycles with minimized charge discharge overpotential and exhibited an avg. coulombic efficiency of 96.78 % which is superior than pristine. Thus, Bi2O3 felt is a prominent anode material for improving the electrochemical performance of zinc based redox flow batteries.

Thickness-dependent microstructure, resistive switching, ferroelectric, and energy storage properties of pulsed laser deposited 0.85[0.6Ba(Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3]-0.15SrTiO3 thin films

In this work, we have studied the effect of thickness on structural, morphological, resistive switching (RS), ferroelectric, and energy storage properties of 0.85[0.6Ba (Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3]-0.15SrTiO3 (BZCT-STO) thin films deposited by the pulsed laser deposition technique. X-ray diffraction (XRD) analysis suggests that BZCT-STO thin films exhibit a polycrystalline tetragonal structure. The lattice parameters and tetragonality ratio approaching to bulk value with an increase of thickness, confirm strain relaxation in thicker films. SEM analysis reveals a dense columnar structure with a different grain size that varies from 3 nm to 60 nm as thickness increased from 160 to 360 nm. The P-E loops suggest that the relaxor behaviour increases with a decrease of thickness due to interface low dielectric layer, substrate clamping effect, small grain size, and high back switching ratio. The RS effect observed in Pt/BZCT-STO/Au capacitors is attributed to polarization modulation of the Schottky barrier and is found to be significant at low thickness. The effect of electric field and frequency on energy storage properties of BZCT-STO films is also investigated. The Pt/BZCT-STO/Au capacitor with a thickness of 160 nm exhibited 6.0 J/cm3 with an efficiency of 72% at a field of 800 kV/cm. It also exhibited a robust energy storage performance in the frequency range of 50–2000 Hz and also up to 108 cycles passing through the capacitor.

Study on physical properties of nanostructured ZnO prepared by pulse laser deposition

Zinc Oxide thin film of 2 μm thickness has been grown on glass substrate by pulsed laser deposition technique at substrate temperature of 500 oC under the vacuum pressure of 8×10-2 mbar. The optical properties concerning the absorption, and transmission spectra were studied for the prepared thin film. From the transmission spectra, the optical gap and linear refractive index of the ZnO thin film was determined. The structure of the ZnO thin film was tested with X-Ray diffraction and it was formed to be a polycrystalline with many peaks.

Resistive switching behavior in ZnO:Ca thin films deposited by a pulsed laser deposition technique

Calcium-doped ZnO (CZO) nanopowders were synthesized using the sol–gel method. The structural characteristics were investigated by X-ray diffraction (XRD) and the analysis reveals that our samples are crystalized in a wurtzite hexagonal structure. The morphological properties and the chemical composition of the nanoparticles were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The obtained powders are stoichiometric with crystallites in a nanometric scale aggregated in micrometric particles. Then, pulsed laser deposition (PLD) technique was used to grow Ca-doped ZnO thin films with different doping concentrations (1, 3, and 5%), on p-type Si substrates. The Ca doping effect on the electrical properties of the CZO films was investigated by current–voltage characteristics. A resistive switching (RS) effect was observed in the ITO/ZnO:Ca/Au structures. The RS behavior is dependent on the Ca doping concentration. The charge transport mechanisms of the devices were studied. In the positive bias voltage region, the transport is dominated by Ohmic and space-charge limited conduction mechanisms under low and high electric fields, respectively.

Structural, magnetic and magnetocaloric properties of hexagonal MnCoGe-based thin films

The characteristic size of the magnetocaloric materials in magnetic refrigerators, thermomagnetic regenerators and energy harvesters is usually down to micrometer and nanometer length scales, which provides the largest possible contact surface area to the heat transfer liquid. Therefore, it is pivotal to investigate the structural, magnetic and magnetocaloric properties of magnetocaloric materials at micrometer and nanometer length scales. In the present study, we have successfully fabricated MnCoGe-based thin films using the pulsed laser deposition (PLD) technique. The as-deposited film shows a dense surface, homogeneous chemical distribution and a preferred orientation along the c-axis of the hexagonal Ni2In-type structure. In-situ temperature-dependent X-ray diffraction measurements on the as-deposited films reveal an irreversible structural degradation above 300 °C due to the considerable evaporation of the Mn atoms, which causes the formation of microscale pores in the films. The thermomagnetic behavior of the film annealed at 250 °C displays a reversible second-order ferromagnetic transition of the hexagonal phase at Curie temperature TC = 275 K, and a first-order hexagonal-orthorhombic structural transition below 200 K. The decoupling of the magnetic and structural transitions brings reversible magnetocaloric effect with the entropy change ΔS values of 2.5 J/(kgK) and the refrigeration capacity reaching 89 J/kg in Δμ0H = 5 T, which are comparable to other reported magnetocaloric thin films. Moreover, antiferromagnetic coupling in the low-temperature orthorhombic phase was observed, which has rarely been reported in the MnCoGe-based bulk alloys. The different magnetic ground states between the thin film and the bulk alloys may be originated from the strain effect imposed by the Al2O3 substrate. Consequently, this work not only provides insights into the structural, magnetic and magnetocaloric properties of the MnCoGe-based alloys at a nanometer length scale, but also offers a new idea for tailoring the multifunctional properties for this material family.

Nanosecond laser irradiation of Yttria stabilized Zirconia: Pulsed laser ablation and surface treatment

Nanosecond pulsed laser irradiation resulting in material ablation and surface micro structuring of Yttria Stabilized Zirconia (YSZ) targets, has been investigated. Our study aims to evaluate suitable ablation conditions enabling either, creation of desired YSZ surfaces having micro porosity for directed use, or generation of YSZ vapors for deposition of homogenous, dense and particle free YSZ films via conventional Pulsed Laser Deposition (PLD) technique. The work being reported here involves a thermal model based theoretical simulation describing heat transport, melting and vaporization of a laser irradiated YSZ target. Our simulation has been validated against our experimental data on nanosecond laser ablation from a sample target of ceramic YSZ. Surface porosity generated on laser irradiated YSZ targets for low laser fluence levels ∼ 1 ​J/cm2 has been explained in terms of pore formation via entrapment of gas bubbles in the solidifying interface on laser melting and re-solidification thereafter, of the YSZ target. To understand surface crater formation on laser irradiated YSZ targets at high laser fluence levels ∼10 ​J/cm2 maximum temperature reached by the laser irradiated YSZ target has been compared with the thermodynamic critical temperature of YSZ. Our study confirms that judicious choice of laser fluence enables either, creation of surfaces having micro porosity of desired nature on YSZ target, or controlled generation of YSZ vapors for deposition of good quality YSZ films and coatings using laser deposition technique.

Nano-Biocomposite Materials Obtained from Laser Ablation of Hemp Stalks for Medical Applications and Potential Component in New Solar Cells

The study in this paper presents a new material that was produced as a thin film by the Pulsed Laser Deposition technique (PLD) using a 532 nm wavelength and 150 mJ/pulse laser beam on the hemp stalk as target. The analyses performed by spectroscopic techniques (Fourier Transform Infrared Spectroscopy-FTIR, Laser-Induced Fluorescence Spectroscopy-LIF, Scanning Electron Microscopy coupled with Energy Dispersive X-ray-SEM-EDX, Atomic Force Microscopy-AFM and optical microscope) evidenced that a biocomposite consisting of lignin, cellulose, hemicellulose, waxes, sugars and phenolyc acids p-coumaric and ferulic, similar to the hemp stalk target was obtained. Nanostructures and aggregated nanostructures of 100 nm to 1.5 μm size were evidenced. Good mechanical strength and its adherence to the substrate were also noticed. It was noticed that the content in calcium and magnesium increased compared to that of the target from 1.5% to 2.2% and from 0.2% to 1.2%, respectively. The COMSOL numerical simulation provided information on the thermal conditions that explain phenomena and processes during laser ablation such as C-C pyrolisis and enhanced deposition of calcium in the lignin polymer matrix. The good gas and water sorption properties due to the free OH groups and to the microporous structure of the new biocomposite components recommends it for studies for functional applications in medicine for drug delivery devices, filters in dialysis and for gas and liquid sensors. Functional applications in solar cells windows are also possible due to the conjugated structures of the contained polymers.

Sub-ps Pulsed Laser Deposition of Boron Films for Neutron Detector Applications.

In view of the demand for high-quality thermal neutron detectors, boron films have recently attracted widespread research interest because of their special properties. In this work, we report on the deposition of boron films on silicon substrates by sub-picosecond pulsed laser deposition (PLD) at room temperature. Particular emphasis was placed on the investigation of the effect of the laser energy density (fluence) on the ablation process of the target material, as well as on the morphological properties of the resulting films. In addition, based on the study of the ablation and deposition rates as a function of the fluence, the ablation/deposition mechanisms are discussed. We show that well-adherent and stable boron films, with good quality surfaces revealing a good surface flatness and absence of cracks, can be obtained by means of the PLD technique, which proves to be a reliable and reproducible method for the fabrication of thick boron coatings that are suitable for neutron detection technology.

Interfacial interaction driven enhancement in the colossal magnetoresistance property of ultra-thin heterostructure of Pr0.6Sr0.4MnO3 in proximity with Pr0.5Ca0.5MnO3

The ultra-thin heterostructure of Pr0.6Sr0.4MnO3(15 nm)/Pr0.5Ca0.5MnO3(15 nm)/SrTiO3 fabricated using pulsed laser deposition technique exhibits the phase-segregated nature wherein the ferromagnetism of Pr0.6Sr0.4MnO3, and the antiferromagnetic state of Pr0.5Ca0.5MnO3 coexist in proximity. The observation of two exciting phenomena in the grown ultra-thin heterostructure, namely, the kinetic arrest and training effect, confirms its phase-segregated nature. The melting of the antiferromagnetic state in Pr0.5Ca0.5MnO3 into a ferromagnetic state due to the interfacial interaction arising from the magnetic proximity of the ferromagnetic clusters of Pr0.6Sr0.4MnO3 have been observed. A metal–insulator transition (TMIT) found at 215 K, close to its Curie temperature (TCurie) observed at 230 K, reveals a strong correlation between the electrical transport and the magnetization of the ultra-thin heterostructure. The electrical conduction in the high-temperature regime is explained in terms of the adiabatic small polaron hopping model. While the resistance in the metallic regime for temperatures above 100 K is contributed by the inelastic scattering due to the two-magnons, in the metallic regime below 100 K, the one-magnon inelastic scattering contribution is prevalent. An enhanced colossal magnetoresistance property near room temperature is obtained in the ultra-thin heterostructure arising from the proximity-driven interfacial interaction, making it a suitable candidate for technological applications near room temperature.

The Effect of Atomization Force on the Structural Properties of NiTi Thin Films

A study using a pulsed laser deposition (PLD) technique was accomplished by growing NiTi nanoparticles on glass and stainless steel 316L substrates. The effects of laser energy state of deposition on the granule size of the NiTi nanoparticle and the structural properties of its thin film were discussed. X-ray diffraction analyses revealed that the films prepared at 65[Formula: see text]W, 75[Formula: see text]W, 85[Formula: see text]W, 100[Formula: see text]W exhibited amorphous structures. AFM results confirmed that the thin films consist of evenly distributed spherical particles. The results also showed an exponential increase in those particles’ sizes.

Laser‐Assisted Growth of Fe3O4 Nanoparticle Films on Silicon Substrate in Open Air

This work presents a growth of Fe3O4 nanoparticle films on silicon substrate. The iron oxide is deposited applying a pulsed laser deposition technique. The process is performed in open air in the absence and presence of external magnetic field. In fact, the morphologies of the obtained Fe3O4–Si samples are similar. The Fe3O4 nanoparticles are spherical with average diameters of 30 nm and are densely agglomerated on the Si substrate. The Fe3O4–Si material prepared in the absence of magnetic field has revealed more intense signals during X‐ray diffraction and Raman measurements. The magnetic investigations indicate that the Fe3O4 nanoparticles are significantly coupled with the Si substrate and do not exhibit superparamagnetic behavior. Moreover, the Verwey transition is 98 K for both investigated Fe3O4–Si samples.