Glow Discharge Reactor Research Articles

Thickness Dependent Direct Current Electrical Conduction in Plasma Polymerized Pyrrole Monolayer Thin Films

The thickness dependent direct current electrical conduction mechanism in plasma polymerized pyrrole (PPPy) monolayer thin films has been discussed in this paper. A parallel plate capacitively coupled glow discharge reactor was used to deposit PPPy thin films at room temperature onto glass substrates. The Fourier Transform Infrared (FTIR) analyses showed that the spectrum of PPPy is very much different than that of the pyrrole monomer and indicated that the monomer has undergone the re-organization during the plasma polymerization. The current density-voltage (J-V) characteristics of PPPy monolayer thin films of different thicknesses indicated an increase in electrical conductivity in the thin films of lower thickness. It is seen that in the low voltage region, the current conduction obeys Ohms law while the charge transport phenomenon appears to be the space charge limited conduction (SCLC) in the higher voltage region. The permittivity, free charge carrier density, and the mobility of the charges of the PPPy monolayer thin films have been calculated from the experimental data of J-V characteristics and found to be 1.07 × 10-10 C2N-1m-2, (3.56 ± 0.01) × 1022 m-3, (4.4 ± 0.01) × 10-19 m2 V-1s-1 respectively.

Effect of Aging on the Optical Properties of Plasma Polymerized 1,1,3,3‐Tetramethoxypropane Thin Films

ABSTRACTPlasma‐polymerized 1,1,3,3‐tetramethoxypropane (PPTMP) thin films of pale brown color were prepared using a capacitively coupled glow discharge reactor. The Fourier transform infrared spectroscopic investigation revealed that PPTMP thin films might have a certain amount of conjugation. Optical properties were investigated by ultraviolet–visible spectroscopic measurements on as‐deposited and aged PPTMP thin films. From the optical absorption data, absorption coefficient and direct and indirect energy band gaps were calculated for the as‐deposited unaged and aged PPTMP thin films. The aging effect on the structural and optical properties is also discussed. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2013, 32, 21347; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21347

Nanocrystalline silicon thin films prepared by low pressure planar inductively coupled plasma

The present work deals with the optimization of nano-crystalline silicon films at a low substrate temperature, using planar inductively coupled low pressure plasma CVD. The films have been produced at 300°C using 1.5sccm SiH4 diluted by 50.0sccm H2 in the rf glow discharge reactor. By varying the gas pressure in the plasma from a very low (15mTorr) to moderate value (200mTorr), nC-Si films with high crystalline volume fraction, φc=86%, could be prepared. The preferred crystallographic orientation of the silicon crystallites gradually changes from 〈111〉 towards 〈220〉 at an optimum pressure of 50mTorr. At higher pressure, the material quality is deteriorated in terms of crystalline volume fraction, network density and surface roughness, due to intense etching by atomic hydrogen on the growing surface. While at very low pressure the precise development of the material is hampered due to very low density of the available precursors as well as low H+ and atomic H density. The nC-Si films with grain size down to 4–5nm, having crystalline volume fraction φc ~36%, are produced by varying the rf-power applied to the substrate at an optimum gas pressure. The nC-Si films exhibit photoluminescence in the visible region. The blue shift of PL peak position with the decrease in grain size during lowering of rf power identifies the quantum confinement phenomena occurring in the silicon grains within nano dimension.

Heat treatment and aging effect on the structural and optical properties of plasma polymerized 2,6-diethylaniline thin films

The monomer, 2,6-diethylaniline has been used to deposit plasma polymerized 2,6-diethylaniline (PPDEA) thin films at room temperature on to glass substrates by a capacitively coupled parallel plate glow discharge reactor. A comparative analysis on the changes of morphological, structural and optical properties of as-deposited, heat treated and aged PPDEA thin films is ascertained. Scanning electron microscopy shows uniform and pinhole free surface of PPDEA thin films and no significant difference in the surface morphology is observed due to heat treatment. Electron dispersive X-ray and Fourier transform infrared spectroscopic investigations indicate some structural rearrangement in PPDEA thin films due to heat treatment. Differential thermal analysis, thermogravimetric analysis and differential thermogravimetric analysis suggest that the PPDEA is thermally stable up to about 580K. The study on the optical absorption spectra of as-deposited, heat treated and aged PPDEA thin films of different thicknesses lead to the determination of the allowed direct and indirect transition energies ranging from 3.63 to 2.73 and 2.38 to 1.26eV respectively. Urbach energy, steepness parameter and extinction coefficient are also assessed. It is observed that the optical parameters of as-deposited PPDEA thin films change due to heat treatment and do not change appreciably due to aging.

The Potential of Nitrogen Rich Surfaces to Distinguish between Cells of the Nucleus Pulposus and Annulus Fibrosus

Introduction Mesenchymal stem cells (MSCs) have been proposed for the purposes of tissue engineering and repair of intervertebral disk (IVD) tissue. These cells would be induced to differentiate into cells with a disc-cell like phenotype, as an alternative treatment for against disk degeneration. One major drawback is that there currently exists no simple way to distinguish a nucleus pulposus (NP) cell from its annulus fibrosus (AF) or hyaline cartilage counterparts. In addition, immature NP cells produce similar macromolecules to those of hyaline cartilage1; therefore, it is difficult to confirm MSCs differentiation into a disk cell phenotype. Our previous studies have shown that surfaces rich in primary amines, -NH2, can influence the adhesion properties of cells.2 In this study, we created reproducible NH2-rich surfaces by low-pressure plasma polymerization of ethylene-ammonia mixture (so-called “L-PPE: N”) to test the hypothesis that selective adhesion of disk cells can be used to distinguish between an NP and an AF phenotype. This would serve as a marker to distinguish an appropriate NP, generated by tissue engineering techniques, from other cartilaginous phenotypes that may be inappropriate for function in the disc. Materials and Methods Surface preparation L-PPE: N coatings approximately 100 nm thick were prepared as previously described.3 These deposits, which contain about 7.5% NH2, were deposited on poly(ethylene terephthalate) (PET) film in a low-pressure (L) capacitively coupled radio-frequency glow-discharge plasma reactor. However, half of the films' surfaces were masked, so as to remain uncoated, bare PET. Cell isolation and culture Adult bovine tails (2 to 3 years old) were obtained 2 hours after slaughter at a local abattoir. The IVDs were dissected from their adjacent vertebral bodies and separated into nucleus pulposus (NP) and AF. Both tissues of the AF and the NP were first weighed (wet weight) and then subjected to a pronase digestion (0.2% W/V), followed by a digestion of collagenase 1A (0.04% W/V) for NP tissue and collagenase II (0.04% W/V) for AF tissue. After isolation, the AF cells and the NP cells were separately cultured on the half-coated surfaces in DMEM high glucose, supplemented with 10% FBS and 1% penicillin/streptomycin in a concentration of 1 × 106 cells/mL. Regular polystyrene culture dishes (TCPS) were used as a control. After 4 days of culture, cells were washed with ddH20, fixed and stained with Safranin-O. Images were captured of both cell types before and after wash, using an optical microscope. Results AF cells adhered preferentially to the L-PPE: N-coated surface, but did not adhere to the bare part of the PET surface (Fig. 1). NP cells, however, indiscriminately adhered to both PET and L-PPE: N surfaces. Both NP and AF cells adhered to regular TCPS dishes after 4 days. After washing with ddH20, which was meant to remove any nonadherent cells, and to provide a clearer image to be captured, AF cells remained bound to L-PPE:N surfaces; however, NP cells were completely removed from both surfaces. Conclusion In this study, we show that AF cells adhered preferentially to the substrate's portion that was L-PPE: N-coated, whereas NP cells did not manifest any preference to coated or uncoated portions. This preferential attachment to an amine-containing surface can be used to distinguish NP from AF cells; together with the production of a high GAG-to-hydroxyproline (proteoglycan-to-collagen) ratio by NP cells, it could help in identifying an NP-like phenotype. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared Mwale F, et al. European Cells and Materials 2004;8:58–64 Girard-Lauriault PL, et al. Macromolecular Bioscience 2009;9:911–921 Girard-Lauriault PL, et al. Plasma Processes and Polymers 2005;2:263–270

Direct current electrical characterization of plasma polymerized pyrrole-N,N,3,5 tetramethylaniline bilayer thin films

The direct current conduction mechanism in plasma polymerized pyrrole-N,N,3,5 tetramethylaniline (PPPy-PPTMA) bilayer thin films has been discussed in this article. A parallel plate capacitively coupled glow discharge reactor was used to deposit PPPy, PPTMA, and PPPy-PPTMA thin films at room temperature onto glass substrates. The Fourier Transform Infrared analyses showed that the PPPy-PPTMA bilayer thin films contained the structural characteristics of both the PPPy and PPTMA. The current density-voltage characteristics of PPPy-PPTMA bilayer thin films of different deposition time-ratios indicated an increase in electrical conductivity as the proportion of PPTMA was increased in the bilayer films. It is also observed that the conductivity of the bilayer thin film is reduced compared with its component thin films. It is seen that in the low voltage region the current conduction obeys Ohm's law, while the charge transport phenomenon appears to be the space charge limited conduction in the higher voltage region. The mobility of the charges, the free charge carrier density, and the permittivity of the PPPy, PPTMA and PPPy-PPTMA bilayer thin films have been calculated. The permittivity for PPPy, PPTMA and PPPy-PPTMA bilayer thin films were found to be 1.07 × 10−10, 2.2 × 10−11, and 1.26 × 10−10 C2 N−1 m−2, respectively; the free charge carrier density were (3.56 ± 0.01) × 1022, 2 × 1021 and (5.19 ± 0.02) × 1022 m−3 respectively; and the mobility of the charges were found to be (4.4 ± 0.01) × 10−19, 1.3 × 10−13 and (2.1 ± 0.01) × 10−19 m2 V−1 s−1 respectively. PACS: 72.80.Le, 73.21.Ac, 73.40.Rw, 73.50.Gr, 73.61.Ph. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

An improved multi-anode contact glow discharge electrolysis reactor for dye discoloration

To promote treatment efficiency of organic pollutant, an improved multi-anode contact glow discharge reactor was developed for dye discoloration. This paper investigated how and what extent multi-anode contact glow discharge electrolysis (m-CGDE) could improve the discoloration efficiency of Acid Orange 7 (AO). I– V characteristic of m-CGDE was also studied in details. It was found that the critical voltage of m-CGDE was same to that of single anode. The concentration of H 2O 2 in the anolyte and discoloration rates of AO increased with increasing treatment time and anode number. Furthermore, an improved m-CGDE reactor was designed by replacing platinum wire with stainless steel wire. Under the same conditions, multiple stainless steel anodes greatly enhanced the discoloration of AO. The trace amount of iron ion from stainless steel anodes played Fenton-like reaction important role.

Comparison of the surface tension of 5.25% sodium hypochlorite solution with three new sodium hypochlorite‐based endodontic irrigants

To investigate the surface tension characteristics of 5.25% sodium hypochlorite and three recently introduced sodium hypochlorite solutions, which had been modified to reduce their surface tension: Chlor-Xtra, Hypoclean A and Hypoclean B. Freshly produced MilliQ water was used as a reference liquid. All measurements of surface tension were taken by the Wilhelmy plate technique, using a Cahn DCA-322 Dynamic Contact Angle Analyzer at the temperature of 22 °C. A glow-discharge cleaned glass slide was immersed in 5 mL of the test liquid in a beaker cleaned with hot chromic acid, rinsed with MilliQ water and finally air plasma-cleaned in a glow-discharge reactor. The force on the glass slide was recorded continuously by the instrument software as the beaker was raised and withdrawn at the constant speed of 40 micron/s, until at least 1 cm of the glass slide was immersed. The typical accuracy was 0.5 mJ m(-2). For each sample, fifteen measurements were taken, and mean values were calculated. A Kruskal-Wallis anova analysis, followed by Mann-Whitney's U rank sum test for pair-wise comparisons, was used to compare surface tension values. Statistical significance was set at α = 0.05. MilliQ water (72.13 mJ m(-2)) and 5.25% sodium hypochlorite (48.90 mJ m(-2) ) had the highest surface tension values (P < 0.01) compared to Chlor-Xtra (33.14 mJ m(-2)), Hypoclean B (30.00 mJ m(-2) ) and Hypoclean A (29.13 mJ m(-2)). Hypoclean A had the lowest surface tension (P < 0.01). The new 5.25% sodium hypochlorite solutions modified with surfactants, Hypoclean A and Hypoclean B, had surface tension values that were significantly lower (P < 0.01) than Chlor-Xtra and 5.25% NaOCl. Because of their low surface tension and increased contact with dentinal walls, these new irrigants have the potential to penetrate more readily into uninstrumented areas of root canal system as well as allow a more rapid exchange with fresh solution, enabling greater antimicrobial effectiveness and enhanced pulp tissue dissolution ability.

DIELECTRIC PROPERTIES OF PLASMA POLYMERIZED N,N,3,5 TETRAMETHYLANILINE THIN FILMS

Plasma polymerized thin films of aluminium/thin film/aluminium configuration were deposited at room temperature by a parallel plate capacitively coupled glow discharge reactor using N,N,3,5 tetramethylaniline (TMA) as a precursor. The infrared spectroscopic analyses revealed that plasma polymerized TMA (PPTMA) films contained an aromatic ring structure with NC and CH side groups, presence of C = O was also evident. The differential thermal analysis and thermogravimetric analysis of PPTMA thin film was thermally stable up to about 505 K. The scanning electron microscopy of PPTMA thin film showed a smooth, flawless and pinhole free surface. The capacitance and ac electrical conductance of PPTMA thin films were measured as functions of frequency (100 &lt; f &lt; 105 Hz) and temperature (300 &lt; T &lt; 450 K). The electrical conductivity is more dependent on temperature in the low frequency region than that in the high frequency region. In PPTMA thin films the conduction may be dominated by hopping of carriers between the localized states at low temperatures and thermally excited at the high temperatures. The activation energies are estimated to be about 0.05 eV in the low temperature and 0.23 eV in the high temperature. Dielectric constant decreases with the increase of frequency and that decreases with the increase of temperature but dielectric loss increases with increasing frequency with a minimum in the low frequency region. The temperature-dependence of the Cole-Cole diagram shows the existence of distribution of dielectric relaxation times in the PPTMA thin films.

Electrical transport mechanism in plasma polymerized 2, 6, diethylaniline thin films

Plasma polymerized 2, 6, diethylaniline (PPDEA) thin films were deposited at room temperature on to glass substrates by a capacitively coupled parallel plate glow discharge reactor. The surface of the PPDEA thin films has been found uniform and pinhole free from the scanning electron micrographs. The observation by electron dispersive X-ray analysis indicates the presence of carbon, nitrogen and oxygen in the PPDEA thin films. The current density–voltage characteristics of aluminum (Al)/PPDEA/Al structure of different film thicknesses have been studied at different temperatures. In the low voltage region, the conduction current obeys Ohm's law while the charge transport phenomenon appears to be Schottky type in the higher voltage region. The temperature dependence of the current density for different bias voltages was also investigated which confirms the possibility of Schottky emission in PPDEA thin films as well.

Parametric Study for Selective Growth of Single-Walled Carbon Nanotubes in Plasma Enhanced Chemical Vapor Deposition

Carbon nanotube (CNT) growth mechanism in plasma enhanced chemical vapor deposition (PECVD) is presented. Previously developed atmospheric pressure glow discharge reactor was modified and used for this purpose. First, pressure-dependent transition (20–100 kPa) of CNT morphology was investigated with fixed input power (60 W) and different catalyst loading (Fe/Al2Ox: 20 nm). High-purity, vertically-aligned single-walled CNTs (SWCNTs) were synthesized when capacitively coupled non-thermal plasma was generated at atmospheric pressure. On the other hand, fraction of double-walled and multi-walled CNTs increased as total pressure decreased. Although CNT growth rate was decelerated at reduced input power (5–20 W), SWCNTs were also synthesized in the root growth regime at 20 kPa. Plasma-generated reactive species are the important driving force of CNT growth; however, generation and transportation of those species must be properly suppressed for selective growth of single-, double-, and multi-walled CNTs.

Microsecond time-resolved Fourier transform infrared analytics in a low pressure glow discharge reactor

A low pressure glow discharge reactor has been designed to allow time-resolved infrared spectroscopic investigation of the discharge zone in practical conditions. The benefits of such reactor are demonstrated through the study of the evolution in the infrared spectra of air/CO(2) gas mixture at the microsecond time-scale. It has been shown that the spectra are greatly affected by the electrical discharge in the 2400-2200 cm(-1) region, where the asymmetric stretch mode of CO(2) falls. The CO(2) molecules are excited through a collision with excited N(2) molecules, where the transfer of energy occurs by a resonant effect. The mechanisms involved are reversible and following plasma pulses.

Conversion of natural gas to C 2 hydrocarbons via cold plasma technology

The plasma technology served as a tool in unconventional catalysis has been used in natural gas conversion, because the traditional catalytic methane oxidative coupling reaction must be performed at high temperature on account of the stability of methane molecule. The focus of this research is to develop a process of converting methane to C 2 hydrocarbons with non-equilibrium plasma technology at room temperature and atmospheric pressure. It was found that methane conversion increased and the selectivity of C 2 hydrocarbons decreased with the voltage. The optimum input voltage range was 40-80 V corresponding to high yield of C 2 hydrocarbons. Methane conversion decreased and the selectivity of C 2 hydrocarbons increased with the inlet flow rate of methane. The proper methane flow rate was 20-40 ml/min (corresponding residence time 10-20 s). The experimental results show that methane conversion was 47% and the selectivity of C 2 hydrocarbons was 40% under the proper condition using atmospheric DBD cold plasma technology. It was found that the breakdown voltage of methane V B was determined by the type of electrode and the discharge gap width in this glow discharge reactor. The breakdown voltage of methane V B, min derived from the Paschen law equation was established.

Direct current electrical conduction mechanism in plasma polymerized thin films of tetraethylorthosilicate

The plasma polymerized tetraethylorthosilicate (PPTEOS) thin films were deposited on to glass substrates at room temperature by a parallel plate capacitively coupled glow discharge reactor. The current density–voltage ( J– V) characteristics of PPTEOS thin films of different thicknesses have been observed at different temperatures in the voltage region from 0.2 to 15 V. In the J– V curves two slopes were observed — one in the lower voltage region and another in the higher voltage region. The voltage dependence of current density at the higher voltage region indicates that the mechanism of conduction in PPTEOS thin films is space charge limited conduction. The carrier mobility, the free carrier density and the total trap density have been calculated out to be about 2.80 × 10 − 15 m 2V − 1 s − 1 , 1.50 × 10 22m − 3 and 4.16 × 10 33m − 3 respectively from the observed data. The activation energies are estimated to be about 0.13 ± 0.05 and 0.46 ± 0.07 eV in the lower and higher temperature regions respectively for an applied voltage of 2 V and 0.09 ± 0.03 and 0.43 ± 0.10 eV in the lower and higher temperature regions respectively for an applied voltage of 14 V. The conduction in PPTEOS may be dominated by hopping of carriers between the localized states at the low temperature and thermally excited carriers from energy levels within the band gap in the vicinity of high temperature.

Comprehensive simulation of the effects of process conditions on plasma enhanced chemical vapor deposition of silicon nitride

A numerical model for the deposition of silicon nitride using silane and ammonia mixture in a radio frequency plasma reactor has been developed. Plasma enhanced chemical vapor deposition process is simulated by combined analysis for the glow discharge, fluid flow and chemical reactions. The main goal is to investigate the effect of variations of the process parameters on the deposition rate, and uniformity of the resulting layer. The approach used is based on the theoretical partial differential equation models, without any empirical approximation of the critical data being used. Owing to the fact that the relevant equations are highly nonlinear, the discretization method is of great importance. A finite boxes method is used to solve the partial differential equations (PDEs), and a Scharfetter–Gummel method is used to discretize the electron and ion flux terms.

On the Mechanism of Nitrogenated Carbon Film Deposition by PACVD in the Presence of Nitrogen. A Cryo‐Trapping Assisted Mass Spectrometric Study

AbstractThe well‐documented effect of film inhibition/perturbation that nitrogen molecules have in the plasma‐assisted (PA)CVD of a‐C/N:H films in a DC glow discharge reactor under low pressure is investigated. Plasma parameters, gas‐phase composition, and film characteristics are recorded using several diagnostic techniques, including the newly developed cryo‐trapping assisted mass spectrometry (CTAMS). Five gas mixtures are investigated; CH4/H2, CH4/N2/H2, and CH4/Ar/H2 as precursors for the films, at low relative concentration of the hydrocarbon molecule (methane), and H2/N2 and He/N2 as film etchers. There are found to be strong differences in the composition of reaction product between systems in which plasma/surface interactions are dominated by ion‐induced processes (sputtering), and those where chemical reactions with nitrogenated species would behave as scavengers of the film precursor. The implications of these findings for the proposed mechanisms of a‐C/N:H film growth are addressed. The application of the scavenger technique for the inhibition of tritium‐containing carbon co‐deposits in the divertor region of fusion reactors, as an international thermonuclear experimental reactor (ITER) in the carbon‐dominated scenarios, is analyzed in the light of these findings.

Effect of substrate on hydrogen in and out diffusion from a-Si:H thin films

We present a detailed study on the effect of the substrate on the structure and hydrogen evolution from p-type hydrogenated amorphous silicon thin films co-deposited on the grounded and RF electrodes of an asymmetric radio frequency glow discharge reactor, as well as the similar films exposed to an hydrogen plasma. We used spectroscopic ellipsometry and hydrogen evolution measurements to analyze the effects of the substrate, ion energy and hydrogen plasma on the films microstructure, thickness, hydrogen content, hydrogen binding and hydrogen evolution. The hydrogen evolution spectra show a strong substrate dependence. In particular on crystalline silicon substrate, we observe the formation of bubbles. For the various substrates, ion energy and hydrogen plasma treatment do not affect the hydrogen evolution spectra. These results indicate that the action of hydrogen in a-Si:H is modified by the nature of the substrate.

Space charge limited conduction in plasma polymerized N, N,3,5 tetramethylaniline thin films

Plasma polymerized N, N,3,5 tetramethylaniline (PPTMA) thin films were deposited at room temperature by a parallel plate capacitively coupled glow discharge reactor. The current density–voltage ( J– V) characteristics of PPTMA thin films of different thicknesses have been investigated at different temperatures. The J– V characteristics show two slopes at the lower and higher voltage regions. It is observed that space charge limited conduction is operative in the higher voltage region in PPTMA thin films. From the experimental studies the carrier mobility, the free carrier density, and the total trap density are found to be about 1.3 × 10 − 13 m 2 V − 1 s − 1 , 2 × 10 21 m − 3 and 4 × 10 30 m − 3 respectively. From the Arrhenius plots of J vs. 1 / T for the applied voltages 2 and 10 V, the activation energies (Δ E) are estimated to be about 0.19 ± 0.02 and 0.85 ± 0.05 eV in the lower and higher temperature regions respectively. At lower temperatures, the available thermal energy is not sufficient to ionize the traps, so hopping mobility is observed. While at higher temperatures, the higher values of Δ E indicate a transition from a hopping process to a distinct energy level process.

Effects of ion energy on the crystal size and hydrogen bonding in plasma-deposited nanocrystalline silicon thin films

We present a detailed study of the effects of the substrate temperature, radio-frequency (rf) power, and total pressure on the crystal size and hydrogen bonding in nanocrystalline silicon thin films codeposited on the grounded and rf electrodes of an asymmetric radio frequency glow discharge reactor. Raman spectroscopy, x-ray diffraction, and spectroscopic ellipsometry measurements show that by varying the deposition parameters we can obtain crystal sizes in the range of 3–10nm and crystalline fractions in the range of 20% up to 97%. The obtaining of small crystallite sizes (4–5nm) in films submitted to high-energy (100–300eV) ion bombardment is highlighted by infrared-absorption and hydrogen evolution measurements, which display characteristic features of hydrogen bonded at the surface of the crystallites. Therefore, hydrogen bonding is a unique way to demonstrate the presence of small crystallites in films at the transition between amorphous and nanocrystalline, films which look amorphous when characterized by standard techniques such as Raman spectroscopy and x-ray diffraction.

Magnetic and transport properties of nanocomposite Fe/Fe3−δO4 and Fe3−δO4 films prepared by plasma-enhanced chemical vapour deposition

Reflective, pinhole-free Fe/Fe3O4 and Fe3−δO4/Fe2O3 nanocomposite films were obtained by reacting iron pentacarbonyl, Fe(CO)5, in an inductively-coupled radio frequency glow discharge reactor. The conductivity of the Fex/(Fe3O4)1−x (x > 7%) composite films exhibits metallic characteristics and the conductivity decreases as the α-Fe content decreases. The metal-to-insulator transition temperature of the Fex/(Fe3O4)1−x (x ∼0.07) films shifts to a higher temperature as compared with Fe3−δO4 due to the increased conductivity from α-Fe. The magnetization versus temperature (M–T) curves show the transition temperature ranging from 95 to 136 K, corresponding to the Verwey temperature, which is dependent on the film composition. The Fe3−δO4 film exhibits a negative magnetoresistance of about 4% and 8% at room temperature and 80 K, respectively.