Mn Films Research Articles

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.

Magnetization switching by spin-orbit torque in crystalline (Ga,Mn)(As,P) film deposited on a vicinal GaAs substrate

Magnetization switching by spin-orbit torque in crystalline (Ga,Mn)(As,P) film deposited on a vicinal GaAs substrate

Synthesis of Mn doped nanostructured zinc oxide thin films for H2 gas sensing

Thin films of zinc oxide and (ZnO:Mn) with 1% and 3% concentrations were created at 400 °C by spray pyrolysis. According to X-ray diffraction (XRD) investigation, ZnO films are polycrystalline and have a cubic structure with a distinct peak in one direction (101). The grain size increases as manganese content rise, from 12.66 nm to 14.66 nm. While the strain (ε) for ZnO reduced after manganese doping, it decreased from 27.36 to 23.63. Surface topography and nanostructure study reveal that as the manganese (Mn) content of ZnO films increased, cluster grain size, average roughness, and root mean square roughness (Rrms) all significantly reduced. SEM images show substantial morphological changes from flat islands to spherical nano-grains post-manganese via Mn content. The average transmittance was >70% in the visible area for Undoped ZnO and 1, 3% Manganese doping optical transmittance demonstrates exceptional optical transparency. When doping levels are increased by 1% or 3%, the absorption coefficient rises. The optical band gap widens in ZnO: Mn film for allowed direct transition has been decreased from (3.32 to 3.21) eV. Results illustrate that the films' refractive index and extinction coefficient decreases with increasing Mn Doped. Hydrogen gas decreases resistance in ZnO films, suggesting p-type behavior. Doping with 3% Mn increases resistance. Decreased sensitivity with higher Mn content after hydrogen gas exposure indicates increased electrical resistance in the film.

Facile synthesis of Mn doped ZnO for the sensing of ammonia

The variation of possessions of Mn doped in ZnO thin films grown by SILAR technique for various Mn concentrations presented. Thin films of Mn doped ZnP were deposited and uniformly annealed at 300 °C for a 30 min. The annealed films are then characterized by various methods like XRD, SEM, EDAX, VSM respectively. The x-ray diffraction studies confirm the emergence of ZnO. From the SEM, various morphologies were identified based on concentration of the solution bath employed. Due to this reason, spherical shoot, rice and flower morphologies were observed on the surface of the films. These morphologies may influence the application of ammonia gas sensor. From compositional analysis (EDAX), the presence of dopant and the variation in composition of doped materials were estimated. Magnetic studies shows, these films show ferromagnetic behaviour at room temperature. The ammonia gas response of the Mn doped ZnO thin films varied with Mn concentration of 0, 5 and 10. The outcomes of the gas sensing experiments showed that the Mn doped ZnO thin film was more sensitive to ammonia, but that sensitivity decreased as gas pressure increased. Ammonia gas showed an increase in the acidic surface properties of Mn-doped ZnO thin film. At room temperature, Mn-doped ZnO (0 %, 5 % and 10 %) showed responses of 19.20, 27.61 and 32.26 to 100 ppm NH3 gas, which were significantly higher than those of ZnO. The Mn-doped ZnO sensor shows excellent selectivity compared to ZnO and has good stability.

Formation of Mn-rich interfacial phases in Co2FexMn1-xSi thin films

We report the formation of Mn-rich regions at the interface of Co2FexMn1-xSi thin films grown on GaAs substrates by molecular beam epitaxy (MBE). Scanning transmission electron microscopy (STEM) with electron energy loss (EEL) spectrum imaging reveals that each interfacial region: (1) is 1–2 nm wide, (2) occurs irrespective of the Fe/Mn composition ratio and in both Co-rich and Co-poor films, and (3) displaces both Co and Fe indiscriminately. We also observe a Mn-depleted region in each film directly above each Mn-rich interfacial layer, roughly 3 nm in width in the x = 0 and x = 0.3 films, and 1 nm in the x = 0.7 (less Mn) film. We posit that growth energetics favor Mn diffusion to the interface even when there is no significant Ga interdiffusion into the epitaxial film. Element-specific X-ray magnetic circular dichroism (XMCD) measurements show larger Co, Fe, and Mn orbital to spin magnetic moment ratios compared to bulk values across the Co2FexMn1-xSi compositional range. The values lie between reported values for pure bulk and nanostructured Co, Fe, and Mn materials, corroborating the non-uniform, layered nature of the material on the nanoscale. Finally, SQUID magnetometry demonstrates that the films deviate from the Slater-Pauling rule for uniform films of both the expected and the measured composition. The results inform a need for care and increased scrutiny when forming Mn-based magnetic thin films on III-V semiconductors like GaAs, particularly when films are on the order of 5 nm or when interface composition is critical to spin transport or other device applications.

Soil redox maps: assessment of small field-scale redox zonation by Mn and Fe oxide-coated IRIS films

PurposeIntra-field redox zonation across depth in soils can be heterogeneous and account for the presence of biogeochemical “hot spots.” Understanding the spatial distribution of hot spots is desirable but hard to obtain.Materials and methodsIn this study, low-cost manganese (Mn) and iron (Fe) oxide-coated Indicator of Reduction In Soils (IRIS) films were installed at a wetland. A grid soil sampling approach within a monitoring plot (20 × 20 m; 2-m raster cells) featured a microrelief of 29 cm above the water table (WT). Data of Mn and Fe oxide removal along IRIS films and natural (newly formed) Fe oxides along Mn IRIS served to spatially resolve digital redox maps by ordinary kriging.Results and discussionA distinctive redox zonation due to the microrelief could be differentiated with the lowest oxide loss at elevated terrain. Located at 9 to 29 cm above the WT, small-scaled pattern of oxide loss of a few cm2 occurred due to anoxic microsites (zone I). Zone II was located at 4 to 9 cm above the WT (Fe2+ sink), whereas zone III extended below and a few cm above the WT (Fe2+ source). Mn IRIS displayed three times more oxide loss, compared to Fe IRIS. Thereupon, natural Fe oxides formed to a major extent along Mn IRIS with on average 80% in redox zone I and II. Thus, Fe2+ was an omnipresent constituent in soil solution, while no or only minor synthetic Fe oxide along Fe IRIS were removed. This highlights the clear difference between the reducibility of pedogenic Fe oxides and synthetic Fe oxides. Overall, the large reactive surface area of IRIS can circumvent problems associated with misclassification of the soil redox status using redox electrodes, which are more susceptible to soil spatial variability.ConclusionsHomogeneity and representativeness of redox sensitive topsoil samples or soil solutions can in fact only be guaranteed within a range < 5 m for this particular study site. IRIS can be utilized to investigate both: microsite-driven features such as neo-formed natural Fe oxides along Mn IRIS (< mm to cm scale) and geo-referenced oxide loss from IRIS at the plot scale (tens to hundreds of meters). Soil redox maps deliver important spatial information for the worldwide growing demand for high-resolution digital soil maps.Graphical

Structural investigations of ZnO nanostructure

Undoped and Mn-doped ZnO samples with different percentages of Mn content (1, 5 and 10 at%) were synthesized by a dip coating sol–gel method. We have studied the structural, chemical and optical properties of the samples by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible spectroscopy. The XRD spectra show that all the samples are hexagonal wurtzite structures. We note that doping favors c-axis orientation along (002) planes. Up to 5 at% of Mn doping level, the c- axis lattice parameter shifts towards higher values with the increase of manganese content in the films. The expansion of the lattice constant of ZnO–Mn indicates that Mn is really doped into the ZnO. The SEM investigations of all samples revealed that the crystallites are of nanometer size. The sur- face quality of the ZnO–Mn film increases with Mn doping but no significant change of the grain size is observed from SEM images. The transmittance spectra show that the trans parency of all the samples is greater than 85 %. We note, also, that a small doping (1 %) lowered the refractive index while the thickness of the layers and the gap increase. However, on raising the proportion of Mn beyond 5 %, practically the same values of index and gap as pure ZnO are found.

In-situ synthesis and performance evaluation of novel color coatings for galvanized steel

Traditional hot-dip galvanized coatings, typically single-silver in color, present increasing aesthetic challenges in diverse applications, while prevailing organic coating methods involve complex processes with high energy consumption and pollution emissions. In this study, a novel hot-dip process for in-situ synthesis of color coating on steel was proposed, capable of producing various uniform color coating. The microstructure of color coatings on steel was systematically examined, and an assessment of their corrosion and weather resistance was conducted. The results demonstrate the sequence of typical color variation is gold, purple, blue, cyan, red, green, and grey. By controlling the immersion temperature range, and regulating the final stable color of the oxide film. The coloration mechanism mainly is attributed to the light interference on the Mn oxide film. The cyan and brown coatings mainly consist of the dense rod-like ζ-FeZn13 phases which provide a structural foundation for corrosion resistance. Furthermore, the brown coating exhibited excellent weather resistance.

Perpendicular magnetic anisotropy and magneto-optical properties of Bi,Mn:YIG epitaxial films

Bi,Mn co-doped Y3Fe5O12 films with good crystallinity, great magneto-optical properties and high perpendicular magnetic anisotropy field (&gt;3000 Oe) were prepared via liquid phase epitaxy.

Suppression of phase segregations in Ge–Fe–Co–Ni–Mn films by high-entropy effect

Fe–Co–Ni–Mn films doped with different concentrations of Ge were prepared on the Si substrates by using radio frequency magnetron sputtering. Transmission electron microscopy (with an energy dispersive x-ray spectrometer) and an x-ray diffractometer were used to systematically study the microstructure evolution of the Fe–Co–Ni–Mn–Ge films. The results indicate that the Fe–Co–Ni–Mn films doped with a large amount of Ge show significant element segregation after rapid high-temperature annealing. However, with the decrease in the doping amount of Ge to approximately equal molar ratio with magnetic elements, Ge and magnetic elements achieve perfect mutual dissolution at the same annealing conditions, forming single-phase solid solution. Electrical transport tests suggest that its electrical property is close to semiconductors. The mechanism of enhanced mutual solubility between semiconductor elements and magnetic elements is discussed in detail.

Comparative study of Cu2XSnS4 (X = Ni, Co, Mn or Fe) films synthesized by spray pyrolysis under air atmosphere, as suitable absorber layers for photovoltaic applications

The present work deals with the synthesis of an absorber Cu2XSnS4 sulfide (X = Ni, Fe, Co or Mn) thin films by a spray pyrolysis method on hot substrate and under air atmosphere for low cost solar cell. Chemical composition analyzes by energy-dispersive X-ray spectroscopy (EDS) revealed the presence of all the chemical elements (Cu, Sn, S and Co, Ni, Mn or Fe) with a composition close to the stoichiometry of the layers of Cu2NiSnS4 (CNTS), Cu2CoSnS4 (CCTS) and far from the stoichiometry for the layers of Cu2MnSnS4 (CMTS) and Cu2FeSnS4 (CFTS). The X-ray diffraction (XRD) analyzes showed the crystallization of the desired phase such as the cubic phase of CNTS with a preferential orientation (111) and the stannite phase of CCTS and CMTS with a preferential orientation (112), except for the CFTS film which is poorly crystallized. SEM analyzes show that CNTS, CCTS and CMTS layers exhibit a rather homogeneous and compact surface with nodule distribution. The CFTS layer surface shows excrescences separated by voids leading to a porous and diffusing surface. The optical analyzes indicated a high absorption coefficient of the order of 104 cm−1 in the visible range for all the layers and an optical band gap of 1.62, 1.58 and 1.64 eV for the layers CNTS, CCTS and CMTS respectively, whereas the direct band gap of CFTS film is higher (∼ 2.23 eV). The comparison of CXTS films synthesized in the same conditions demonstrates that the CNTS and CCTS films have the most suitable features (optical, electrical, mechanical and oxidation resistance) to be used as absorbing layer in low cost solar cell.

Obtaining of thin films of manganese silicides on a Si surface by the method of solid-phase deposition and investigation of their electronic structure

The regularities of the formation of thin Mn/Si (111) nanofilms during solid-phase deposition of Mn on Si under conditions of ultrahigh vacuum ([Formula: see text][Formula: see text]Pa) and thin Mn4Si7/Si (111) nanofilms during annealing of the Mn/Si system have been studied. It has been established that silicon atoms diffuse into the Mn film up to a thickness of [Formula: see text]–12 monolayers, and Mn in Si up to [Formula: see text]–10 monolayers, therefore, a transition layer of nonstoichiometric MnxSiy silicide is formed at the Mn–Si interface. After heating at [Formula: see text][Formula: see text]K, the higher manganese silicide (HMS) Mn4Si7 is formed. In particular, it was found that the bandgap of Mn4Si7is [Formula: see text][Formula: see text]eV, and the electron affinity is [Formula: see text][Formula: see text]eV and in the work, the optimal thermal diffusion conditions for the formation of stoichiometric Mn4Si7 silicide are determined. It is shown that at [Formula: see text][Formula: see text]K, a partial formation of a chemical bond between manganese and silicon atoms occurs. At 1100[Formula: see text]K, a thin Mn4Si7 film with a good stoichiometric composition is formed.

Tunable Phase Structure in Mn-Doped Lead-Free BaTiO3 Crystalline/Amorphous Energy Storage Thin Films

For dielectric energy storage materials, high polarization and high breakdown strengths are a long-standing challenge. A modulating crystalline/amorphous phase structure strategy is proposed by Mn-doping and annealing temperature to enhance the energy storage performance of pure BaTiO3 (BT) films. In this study, lead-free Mn-doped BT films were prepared on Pt/Ti/SiO2/Si substrates via the sol-gel method, and the effects of the crystalline/amorphous phase ratio on polarization and electric properties were analyzed. A small amount of Mn-doping in BT could reduce the annealing temperature and enhance polarization with an Mn content of 8%. In addition, the energy storage properties of BT-8%Mn films achieve the best energy storage performance in terms of energy density and efficiency of 72.4 J/cm3 and 88.5% by changing the annealing temperature to 640 °C. BT-8%Mn energy storage films also possess good stability over a wide temperature range of 20 °C–200 °C, which demonstrates that crystalline/amorphous engineering is a simple and effective way to enhance energy storage applications of dielectric films.

Influence of Mn doping on electrical properties of TiO2/Si heterojunction diode

AbstractIn this special work, two types of material, which are undoped and Mn doped TiO2thin films, have been produced by spin coating technique, and then their structural, morphological and optical properties have been measured at different Mn doping rates. Four different doping ratios, undoped, 1, 3 and 5% Mn doped TiO2have been both experimentally and theoretically investigated and some significant enhancements have been reported. The results of X-ray diffraction (XRD) such as dislocation density, strain, and crystallite size have indicated that undoped, 1, 3 and 5% Mn doped TiO2thin films had the phase of anatase at 450 °C. It has been observed that the peak intensity of 3% Mn doped TiO2films has decreased compared to undoped and 1% Mn doped TiO2while the peak intensity has increased for 5% Mn doped TiO2. The refractive indices and dielectric coefficients of the undoped and Mn doped TiO2thin films have also been calculated. The undoped and Mn doped TiO2/p-Si heterojunction diodes has exhibited photosensitive behaviour in the illuminated environment. 1% Mn doped TiO2/p-Si heterojunction diode indicated the highest photocurrent. The electrical parameters of all diodes have been calculated and compared to the conventionalJ–Vand Norde methods. Additionally, 1% Mn doped TiO2/p-Si heterojunction diode has been modelled by using the SCAPS-1D program, andJphvalues have also been calculated based on the shallow donor density (ND). The experimental and theoreticalJphvalues of this diode were found to be compatible with each other.

Multilevel states driven by spin-orbit torque in a P-composition graded (Ga,Mn)(As,P) film

We have studied spin-orbit torque (SOT) magnetization switching in a (Ga,Mn)(As,P) film with vertically-graded magnetic anisotropy. The magnetization switching chirality during current scans reveals that strain-induced Dresselhaus-type spin-orbit field does the major role for spin polarization of carriers causing SOT in the system. The volume fraction of SOT magnetization switching significantly depends on the magnitude and direction of the applied bias field. This feature leads to the realization of stable multilevel magnetic states in composition-graded (Ga,Mn)(As,P) film. The experiment demonstrates that multiple magnetic state can be robustly set by using appropriate bias fields. This characteristic can be used to realize SOT-driven multi-state memories and/or memristor devices, which are key ingredients for neuromorphic computing.

Formation and Properties of Thermistor Chips Based on Semiconductor 3D Metal Oxide Films Obtained by RF-Magnetron Sputtering

The formation of oxide semiconductor films of the (Mn,Co,Cu)3O4 type by radio frequency magnetron sputtering is presented. The conditions of deposition and subsequent heat treatment make it possible to obtain films with electrophysical characteristics close to those of the bulk ceramic materials used as a target for magnetron sputtering. Two variants of thermistor geometry were implemented. In the first case, the working layer of oxide semiconductor was deposited directly on the dielectric substrate (planar geometry), and in the second case on the layer with high electrical conductivity (Ni or Al) forming the inner electrode (layered geometry). The lower limit of the nominal resistance of the planar thermistor while maintaining high temperature nonlinearity is ~ 10 kΩ. The layered structure with the inner electrode makes it possible to reduce the lower limit of resistance up to ~ 50 Ω without losing the temperature nonlinearity of the thermistor. In addition, heat treatment above 450 °C or current self-heating with sufficient power output leads to the appearance of a pronounced voltage nonlinearity, which increases the thermal constant B of thermistors from 2400-3400 to 5000-5500 K. The fields of application of oxide-film structures for the correction of linear resistors and the implementation of integration approaches in the construction of linearized sensors are discussed.

Synergistic effect enhances energy storage properties of BNT-based relaxor ferroelectric thin films

Lead-free thin film capacitors with high energy density and efficiency are promising candidates for pulse power systems in advanced electronic industries due to their low cost, lightweight, and integration development. In this study, 0.6Bi0.5Na0.5TiO3-0.4Sr0.7Bi0.2TiO3+x mol Mn (BNT-SBT-xMn) thin films are fabricated on Pt/Ti/SiO2/Si substrates via sol-gel method. The BNT-SBT-xMn films with perovskite phase possess uniform grain size, well density, and low roughness. The introduction of Mn ions compensates for valence unbalances of A-site vacancy of BNT-based films and forms defective dipoles. Their synergism hinders the transmission of carriers, reduces the leakage current density, and improves polarization and breakdown behavior. Therefore, the BNT-SBT-2% Mn film achieves a high recoverable energy density of 85.35 J/cm3 together with an enhanced energy efficiency of 73.17% under an electric field of 3114 kV/cm. Meanwhile, the BNT-SBT-2% Mn film displays a good frequency (10 Hz-2k Hz), temperature (20–200 °C), and fatigue (1-105 cycles) stability in electrical energy storage properties, suggesting that it would be a promising candidate for the advanced power systems.

Self-recoverable near-infrared mechanoluminescence from ZnS:Mn by controlling manganese clusterization

Near-infrared (NIR)-emitting mechanoluminescence (ML) materials are highly desirable since they are biological transparency and suitable for deep-imaging inside biological tissues. So far, NIR emission can be found in very limited number ML materials. Moreover, reported NIR ML materials suffer from limitations associated with the incompetence in self-reproducibility. Herein, we observe sustainable and self-recoverable NIR ML emission in pulsed laser deposition (PLD) method grown ZnS:Mn film, for the first time. ML emission in ZnS:Mn can be explained by the piezoelectricity-induced detrapping model. Broad ML emission covering both red and NIR ranges arises from the presence of (Mn)n clusters, which facilitates the energy transfer from excited Mn2+ ions to them. During the PLD growth, high laser fluence and deposition rate contribute to the formation of (Mn)n clusters, which was verified by electron paramagnetic resonance EPR and X-ray photoelectron spectroscopy XPS analysis. The device exhibits durable NIR ML over 105 repeated mechanical stresses, suggesting new possibilities aiming for constructing self-recoverable NIR ML materials.

Spin orbit torque switching of magnetization in the presence of two different orthogonal spin–orbit magnetic fields

Switching of magnetization by spin–orbit torque in the (Ga,Mn)(As,P) film was studied with currents along ⟨100⟩ crystal directions and an in-plane magnetic field bias. This geometry allowed us to identify the presence of two independent spin–orbit-induced magnetic fields: the Rashba field and the Dresselhaus field. Specifically, we observe that when the in-plane bias field is along the current (I ∥ Hbias), switching is dominated by the Rashba field, while the Dresselhaus field dominates magnetization reversal when the bias field is perpendicular to the current (I ⊥ Hbias). In our experiments, the magnitudes of the Rashba and Dresselhaus fields were determined to be 2.0 and 7.5 Oe, respectively, at a current density of 8.0 × 105 A/cm2.

Design and fabrication of thermopower and electrical resistivity setup for bulk and thin film systems

An experimental setup has been designed and fabricated with a new configuration for measuring both thermopower as well as resistivity of different type of samples (bulk and thin film) in the temperature range 80–300 K. The setup utilizes a differential method for measuring the thermopower of samples. The sample holder in the present setup has been designed in such a way that, samples of lengths ∼2.5–15 mm can be loaded easily with the help of spring–shaft arrangement. Electrical leads, as well as controlled ΔT by chromel-AuFe (0.07 %) thermocouple, are mounted on the copper blocks. Manganin wires of resistance 50 Ω are used as heating elements and wound on the copper blocks. Generated emf of the sample and the thermocouple are measured using nanovoltmeter. The present configuration allows simple way of applying temperature difference to bulk and thin film systems. The setup allows continuous ΔT control across the sample by chromel-AuFe (0.07 %) thermocouple to achieve accuracy and precision with the nanovoltmeter, scanner switching system and Visual Basics software programme used for automatic measurements. The measurements are carried on standard bulk samples Mn, Mo and Mo thin film. Results are well in agreement with reported values.