Mn Films Research Articles

New insights into graphite paper as electrocatalytic substrate for oxygen evolution reaction

Designing highly efficient electrocatalysts for oxygen evolution reaction is important to meet the requirement of various renewable energy storage and conversion devices. Generally, the performance of OER catalysts can be significantly improved by synergistic action of the underlying conductive substrate. In this work, a commercial graphite paper was used as a facile substrate with catalytic activity. Graphite paper produced 10mAcm−2 at an overpotential of 447mV with a Tafel slope of 62mVdec−1. By depositing NiFe hydroxide or Mn oxide film onto the graphite paper, the electrode presented a superior activity for water oxidation, which was believed to be synergistically contributed by their available electrochemically active sites associated with the deposited film and the active substrate. High activities were also accompanied by remarkable durability at large current density levels. Our results illustrated a guideline to the design of inexpensive and highly active composite electrode for water oxidation.

Hierarchical Metal Oxide Topographies Replicated from Highly Textured Graphene Oxide by Intercalation Templating.

Confined assembly in the intersheet gallery spaces of two-dimensional (2D) materials is an emerging templating route for creation of ultrathin material architectures. Here, we demonstrate a general synthetic route for transcribing complex wrinkled and crumpled topographies in graphene oxide (GO) films into textured metal oxides. Intercalation of hydrated metal ions into textured GO multilayer films followed by dehydration, thermal decomposition, and air oxidation produces Zn, Al, Mn, and Cu oxide films with high-fidelity replication of the original GO textures, including "multi-generational", multiscale textures that have been recently achieved through extreme graphene compression. The textured metal oxides are shown to consist of nanosheet-like aggregates of interconnected particles, whose mobility, attachment, and sintering are guided by the 2D template. This intercalation templating approach has broad applicability for the creation of complex, textured films and provides a bridging technology that can transcribe the wide variety of textures already realized in graphene into insulating and semiconducting materials. These textured metal oxide films exhibit enhanced electrochemical and photocatalytic performance over planar films and show potential as high-activity electrodes for energy storage, catalysis, and biosensing.

Magnetic Effects in Films of Mn12-Acetate

Pulsed laser deposition has been optimized to deposit Mn12-acetate films. Extensive DC and AC susceptibility measurements on these films reveal the presence of two peaks due to (i) a single molecule spin blocked species below ∼3 K as in crystalline Mn12-acetate, and (ii) a magnetic species at 28 K due to significant additional interactions (below ∼40 K). Lattice deformation and random distribution of magnetic ions resulting from laser ablation may account for the presence of a new species with enhanced magnetic anisotropy leading to a higher transition temperature. Results suggest that the high temperature species stabilizes the spin blocked species and the two-species system may display an exchange bias effect.

Optimizing ductility and fracture of amorphous metal thin films on polyimide using multilayers

Aluminum–manganese (Al–Mn) thin films with manganese concentration up to 20.5 at.% were deposited on polyimide (PI) substrates. A variety of phases, including supersaturated fcc (5.2 at.% Mn), duplex fcc and amorphous (11.5 at.% Mn), and completely amorphous phase (20.5 at.% Mn) were obtained by adjusting alloying concentration in the film. Tensile deformation and subsequent fracture of strained Al–Mn films on PI were investigated experimentally and by finite element simulations. Compared with crystalline and dual phase counterparts, amorphous thin film exhibits the highest fracture stress and fracture toughness, but limited elongation. Based on the fracture mechanism model, a multilayer scheme was adopted to optimize the ductility and the fracture properties of the amorphous film/PI system. It was found that by sandwiching the amorphous film (20.5 at.% Mn) between two ductile Cu layers, the elongation can be improved by more than ten times, and the interfacial fracture toughness by more than twenty times. This design provides important guidelines to obtain optimized mechanical properties of future flexible electronics devices.

Effect of Mn addition on corrosion properties of biodegradable Mg-4Zn-0.5Ca-xMn alloys

The corrosion properties of biodegradable Mg–4Zn–0.5Ca–xMn alloys (x = 0, 0.4, 0.8 wt%) in Hank's solution were investigated. According to the electrochemical measurements, the corrosion resistance of the alloys was effectively improved by Mn addition. In addition, the analysis of corroded surface with high resolution transmission electron microscopy (HR-TEM) and time of flight secondary ion mass spectrometry (ToF-SIMS) revealed that the depth of the corrosion product was decreased by Mn addition. It was observed that the microstructural changes had little effect on corrosion properties and Mn oxide film acts as a helpful barrier against chloride ions penetration.

Defect formation and its effect on electronic structure and magnetic properties of GaN:Mn films

GaN:Mn thin films were fabricated by implanting Mn ions into Mg-doped GaN epilayer. X-ray diffraction study reveals that all the samples are in single phase wurtzite crystalline structure. Raman spectra exhibit additional excitations attributed to the vibrational mode of defects caused by Mn ion implantation and the Mn related local vibrational mode in the vicinity of E2high. The X-ray photoelectron spectroscopy results indicate that the Mn ions were successfully incorporated into the GaN host lattice by substituting the Ga sites. The magnetization curve as a function of the magnetic field at 300K indicates that room ferromagnetisms exist in GaN:Mn thin films. The effect of vacancy defect on the magnetic properties of MnMg co-doped GaN has been studied by first principles calculations. Based upon experimental and theoretical results, it is believed that the alteration of ferromagnetism with annealing temperature is directly related to the variation of magnetic exchange interaction with microstructure in this material system.

Effect of manganese concentration on physical properties of ZnS:Mn thin films prepared by chemical bath deposition

ZnS:Mn thin films were grown by chemical bath deposition technique on glass substrates for different doping ratios y = [Mn2+]/[Zn2+] (y = 0, 6, 12 and 18 at. %). Structural, morphological, optical and electrical properties were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), UV–Vis–NIR spectrophotometry, spectrofluorimetry, Hall effect measurement. In fact, the XRD analysis showed that ZnS:Mn films were poorly crystalline. The average transmittance of all films was greater than 70 % in the visible range. The effect of Mn doping on refractive index, extinction coefficient and other optical parameters was also investigated. Measured electrical resistivity decreased slightly from 7.586 × 104 to 6.819 × 104 Ω cm with increasing of doping concentration from 0 to 6 at. % then it increased again to achieve 16.73 × 104 Ω cm for \(y\) equals to 18 at. %.

Growth of epitaxial Mn and Zn codoped BiFeO3 thin films and an enhancement of photovoltage generated by a bulk photovoltaic effect

Recently, the bulk photovoltaic effect of BiFeO3 (BFO) thin films has attracted much attention because of its above bandgap photovoltage for realizing novel photovoltaic devices. In this study, the epitaxial growth of 1-µm-thick Mn and Zn codoped BFO thin films has been demonstrated, and the effects of Mn and Zn codoping on the ferroelectric and bulk photovoltaic properties of the BFO thin films have been investigated. A 0.5% Mn and 0.5% Zn codoped BFO (BFMZO050) thin film on a SrRuO3-buffered vicinal-SrTiO3(001) substrate showed an atomically flat surface with a step-and-terrace structure, a low leakage current of 1.5 × 10−6 A/cm2 at 100 kV/cm, and well-saturated ferroelectric electric displacement–electric field (D–E) hysteresis loops. In addition, a Pt/BFMZO/Pt coplanar capacitor with an interelectrode distance of 260 µm illuminated by a violet laser (λ = 405 nm) showed an enhanced photovoltage of 145 V owing to the reduction in photoconductance by Mn and Zn codoping.

Квазикласичне та квантове перенесення заряду в полікристалічних плівках $\alpha$-Mn нанометрової товщини

Квазикласичне та квантове перенесення заряду в полікристалічних плівках $\alpha$-Mn нанометрової товщини

Antiferromagnet-induced perpendicular magnetic anisotropy in ferromagnetic/antiferromagnetic/ferromagnetic trilayers

This study demonstrates the effect of antiferromagnet-induced perpendicular magnetic anisotropy (PMA) on ferromagnetic/antiferromagnetic/ferromagnetic (FM/AFM/FM) trilayers and reveals its interplay with a long-range interlayer coupling between separated FM layers. In epitaxially grown 12 monolayer (ML) Ni/Co/Mn/5 ML Co/Cu(001) films, magnetic hysteresis loops and element-resolved magnetic domain imaging showed that the magnetization direction of the top layers of 12 ML Ni/Co films could be changed from the in-plane direction to the perpendicular direction, when the thickness of the Mn films (${\mathrm{t}}_{\mathrm{Mn}}$) was greater than a critical value close to the thickness threshold associated with the onset of AFM ordering (${\mathrm{t}}_{\mathrm{Mn}}=3.5$ ML). The top FM layers exhibited a significantly enhanced PMA when ${\mathrm{t}}_{\mathrm{Mn}}$ increased further, and this enhancement can be attributed to a strengthened AFM ordering of the volume moments of the Mn films, as evidenced by the presence of induced domain frustration. By contrast, the long-range interlayer coupling presented clear effects only when ${\mathrm{t}}_{\mathrm{Mn}}$ was at a lower coverage.

White Light Emission from ZnS:Mn Thin Films Deposited on GaN Substrates by Pulsed Laser Deposition**Supported by the Science and Technology Plan Projects of Colleges and Universities in Shandong Province under Grant No J15LN33, the Scientific Research Foundation of Binzhou University under Grant No BZXYG1512, and the Doctoral Scientific Research Foundation of Binzhou University under Grant No 2014Y15.

ZnS:Mn thin films are grown on GaN substrates by pulsed laser deposition. The structure, morphology and optical properties are investigated by x-ray diffraction, scanning electron microscopy and photoluminescence (PL). The obtained ZnS:Mn thin films are grown in preferred orientation along β-ZnS (111) direction corresponding to crystalline structure of cubic phase. The deposition temperature has an obvious effect on the structure, surface morphology and optical properties of ZnS:Mn thin films. PL measurements show that there are two emission bands located at 440 nm and 595 nm when the films are deposited at temperatures from 100°C to 500°C. The relative integrated intensity of the blue emission and orange-red emission is determined by the deposition conditions. At the proper deposition temperature of 300°C, the color coordinate is closest to (0.33, 0.33). The ZnS:Mn films on GaN substrates can exhibit white light emission.

Structural changes induced spin-reorientation of ultrathin Mn films grown on Ag(001)

The strained body centered tetragonal (bct) Mn ultrathin film from lattice parameter a=2.89Å to lattice value of 2.73Å induces anti-ferromagnetic behavior between Mn layers. The magnetic easy axis of Mn film was demonstrated theoretically to switch from the in-plane to out-of-plane by magneto-optical Kerr effect investigation. By including spin–orbit coupling in full potential linearized augmented plane waves and linearized muffin-tin orbitals methods, manganese ultrathin film displays different magnetic behaviors and the spin-reorientation transition is shown to be correlated to these structural changes. The calculated magnetic moment of manganese planes are enhanced and reach a value of ~4.02μB. The polar magneto-optical Kerr effect is calculated for a photon energy range extended to 15eV. It shows a pronounced peak in visible light.

Synthesis and optical properties of nanostructured ZnS:Mn films

The experimental results on the synthesis of ZnS:Мn nanoparticles, as well as the study of their structure and optical and photoluminescence characteristics, are reported. The ZnS:Мn nanoparticles and thin films on silicon and glass substrates are grown via hydrochemical deposition from the solution containing thiourea, zinc chloride, manganese chloride, and dimethyl sulfoxide. The internal structure of the samples is probed via X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The spectral dependence has allowed a determination of the bandgap width in ZnS:Мn nanoparticles. It is found the photoluminescence peak intensity increases with the enlargement of nanoparticles.

Enhancement in some physical properties of spray deposited CdO:Mn thin films through Zn doping towards optoelectronic applications

This paper reports the enhancement in the structural, morphological and opto-electrical properties of spray deposited CdO:Mn thin films through Zn doping. Mn concentration is maintained as 1 at.% for all the films whereas Zn concentration in CdO:Mn film is varied as 1, 2 and 3wt.%. XRD studies showed that the crystalline quality of pure CdO deteriorates with Mn doping which got enhanced with Zn doping. The entire doped films exhibit a (1 1 1) preferential orientation similar to that of the undoped film. Cauliflower shaped nanostructures are evinced for all the films from the FESEM images. The decreased transparency of pure CdO with Mn doping increases with Zn doping and a maximum transmittance of 89.8% is obtained for the CdO:Mn film coated with 2wt.% Zn concentration. Optical band gap of pure CdO which exhibits a red shift with Mn doping got blue shifted with Zn doping. Electrical studies showed that the CdO:Mn film is more resistive than the undoped film which experience a decrement with Zn doping. The obtained results confirm that CdO:Mn film when doped with zinc finds application in optoelectronic devices due to their enhanced opto-electrical properties.

Effect of Mn doping on the structural, magnetic, optical and electrical properties of ZrO2–SnO2 thin films prepared by sol–gel method

Manganese doped ZrO2–SnO2 (ZrO2–SnO2: Mn) nanocomposite thin films were prepared using sol – gel dip coating technique. The structural, morphological, magnetic, optical and electrical properties of the films were studied for undoped and different (15 mol %) manganese doping concentrations. X-ray diffraction pattern (XRD) of films showed the formation of tetragonal phase of SnO2 and orthorhombic ZrSnO4. Decrease in crystallinity with increase of Mn concentration was observed for the films. Scanning electron microscopy (SEM) showed the formation of grain growth with an increase in Mn concentration. X-ray photo electron spectroscopy (XPS) confirmed the presence of Zr4+, Sn4+ and Mn2+ ion in ZrO2–SnO2: Mn films. Vibrating sample magnetometer (VSM) measurements reveal the presence of magnetic properties in Mn doped nanocomposite thin films. Antiferromagnetic interactions were observed for 5 mol % Mn doping. An average transmittance >80% (UV - Vis region) was observed for all the films. Band gap of the films decreased from 4.78 to 4.41 eV with increase in Mn concentration. Photoluminescence (PL) spectra of the films exhibited emission peaks in visible region of the electromagnetic spectra. Conductivity of the film increased up to 3 mol % Mn doping and then decreased.

Kinetic patterns in the formation of nanosized manganese–manganese oxide systems

Transformations in nanosized manganese films are studied by means of optical spectroscopy, microscopy, and gravimetry at different film thicknesses (d = 4–108 nm) and temperatures of heat treatment (T = 373–673 K). It is found that the kinetic curves of conversion are satisfactorily described in the terms of linear, inverse logarithmic, cubic, and logarithmic laws. The contact potential difference is measured for Mn and MnO films, and photo EMF is measured for Mn–MnO systems. An energy band diagram is constructed for Mn–MnO systems. A model for the thermal transformation of Mn films is proposed that includes stages of oxygen adsorption, the redistribution of charge carriers in the contact field of Mn–MnO, and manganese(II) oxide formation.

Structural and magnetic features of solid-phase transformations in Mn/Bi and Bi/Mn films

Solid-phase transformations at different annealing temperatures in Mn/Bi (Mn on Bi) and Bi/Mn (Bi on Mn) films have been studied using X-ray diffraction, electron microscopy, and magnetic measurements. It has been shown that the synthesis of the α-MnBi phase in polycrystalline Mn/Bi films begins at a temperature of ~120°C and the Mn and Bi layers react completely at 300°C. The resulting α-MnBi(001) samples have a large perpendicular magnetic anisotropy (Ku ≃ 1.5 × 107 erg/cm3) and a coercive force H > HC ~ 3 kOe. In contrast to Mn/Bi, the ferromagnetic α-MnBi phase in Bi/Mn films is not formed even at annealing processes up to 400°C and Mn clusters are formed in a Bi melt. This asymmetry in phase transformations occurs because chemosorbed oxygen existing on the surface of the Mn film in Bi/Mn films suppresses a solid-phase reaction between Mn and Bi. The analysis of the results obtained implies the existence of new low-temperature (~120°C) structural transformation in the Mn–Bi system.

Crystalline Quality and Structure of MBE-Grown Ferromagnetic Semiconductor ZnSnAs2:Mn Thin Films Revealed by High-Resolution X-ray Diffraction Measurements

Abstract The crystalline structure and quality of ZnSnAs2:Mn films grown by molecular beam epitaxy (MBE) on InP substrates are two of the most important issues in preparing spintronic structures such as magnetic quantum wells and spin-based transistors. We conducted high-resolution X-ray diffraction (XRD) measurements to clarify the crystalline structure of ZnSnAs2:Mn thin films. The XRD measurements reveal with very high accuracy that the samples have a sphalerite structure with high epitaxial quality. These results, within the limits of measurement accuracy support the previous assumption that ZnSnAs2:Mn thin films are coherently clustered ferromagnetic semiconductors without breaking the continuity of the sphalerite structure, leading to ferromagnetism with a high Curie temperature close to that of zincblende MnAs.

Effects of glycine and current density on the mechanism of electrodeposition, composition and properties of Ni–Mn films prepared in ionic liquid

The effects of glycine on the mechanism of electrodeposition of Ni–Mn alloy film prepared in ChCl–urea ionic liquid were studied in order to control the composition, microstructure and properties of the film. The cyclic voltammograms revealed that the presence of glycine in the ionic liquid can inhibit the reduction of Ni2+ ions but promote the reduction of Mn2+ ions in the cathodic scan. However, it promoted the dissolution of both Ni and Mn deposits in the ChCl–urea ionic liquids during the reverse scan. Glycine changed the mode of Ni–Mn film growth from Volmer–Weber mode into Stranski–Krastanov mode. The Mn content in the Ni–Mn film increased with the increase of concentration of glycine and current density. The Ni–Mn alloy film with 3.1at.% Mn exhibited the lowest corrosion current density of 3×10−7A/cm2 compared with other films prepared and exhibited better corrosion resistance than pure Ni film in 3.5wt.% NaCl solution.

Photoluminescence and structure of sputter-deposited Zn2SiO4:Mn thin films

Mn-doped Zn2SiO4 thin films were deposited on Si (100) substrates by radio-frequency (RF) magnetron sputtering. The deposited films were then annealed at temperatures ranging from 600 to 1200 °C in an air ambient for 1 hour. The as-deposited Zn2SiO4:Mn films exhibited an amorphous structure having a smooth surface and showed no photoluminescence (PL). Annealing at 600 °C was found to have little effect on the properties of the films. The films still remained amorphous with no PL. After annealing at 800 °C, the films were crystallized in a mixture of orthorhombic β-Zn2SiO4 and rhombohedral α-Zn2SiO4 phases. These films showed a PL emission spectrum that could be resolved into two bands, one centered at 520 nm in the green region and the other at 571 nm in the yellow region. The green PL emission originated from the 4T1 → 6A1 intrashell transition of Mn2+ ions in the α-Zn2SiO4 phase while the yellow emission was attributed to Mn2+ ions in β-Zn2SiO4. The films annealed at and above a temperature of 900 °C exhibited only the α-Zn2SiO4 phase, and the PL spectra of these films showed only the green emission band with a peak maximum at around 523 nm. The PL emission intensity increased with increasing annealing temperature, which was due to the better crystalline quality and the rougher surface morphology of the Zn2SiO4:Mn films annealed at higher temperatures.