Mn Films Research Articles

Mn Doped PbZrTiO3 Thick Films for the Renewable Piezoelectric Energy Harvesters for Mobile Communications

Renewable energy systems including piezoelectric, thermoelectric, and photovoltaic devices have been intensively considered for the for the internet of things. Small energy sources with sustainable and robust properties for sensors, actuators, and communications were indispensable for the next industrial revolution. In this research, Mn doped PbZrTiO3 thick films piezoelectric renewable energy harvesters were prepared and employed for the sustainable energy sources for the energy harvesters. Nano sized powders were prepared by the high energy ball milling process. Calcination and sintering processes were sequentially processed for the device applications. Generated output energies were measured and tested by the impedance matching circuits and applied to the energy sources.

Promoting control of antiferromagnet-induced perpendicular magnetic anisotropy in magnetic multilayers: Effects of applying in-plane magnetic supporting layers

We report that antiferromagnet-induced perpendicular magnetic anisotropy (PMA) occurring in magnetic thin films can be effectively controlled by applying ultrathin in-plane magnetic supporting layers with high ferromagnetic ordering temperature through magnetic proximity effects. In a series of epitaxially grown 12-ML Ni/Co/Mn/Co/Cu(001) films, we observed that the PMA of the top 12-ML Ni/Co films and the long-range antiferromagnetic ordering of Mn film were enhanced concurrently with the establishment of ferromagnetic ordering of the bottom Co film. This clearly proves the underlying mechanism of magnetic proximity effects, and offers another degree of freedom for the control of perpendicular-based magnetic logical devices.

Preparation of hybrid photoelectrode based on defect-poor Zn-CuInSe2 QDs sensitized nanoporous ZnO nanosheets with an application in azo dye removal

The glutathione (GSH) and mercaptopropionic acid (MPA) modified internal defect-rich, surface defects-poor near infrared (NIR) Zn–CuInSe2 (ZCISe) QDs were synthesized. Nanoporous ZnO nanosheets (NS) were firstly loaded with those ZCISe QDs to improve photoelectrochemical response in the NIR light region. Then loading Mn doping CdS thin film onto the ZCISe/ZnO NS was further used to reduce the interfacial recombination between different components of hybrid photoelectrode, in addition to enhance the light absorption and resist the photo-oxidation decomposition of the photocatalysts. Successively introducing ZCISe and Mn–CdS onto ZnO NS can increase the photocurrent intensities from 1 mA/cm2 for naked ZnO NS, 2.2 mA/cm2 for ZCISe/ZnO NS, to 9 mA/cm2 for Mn–CdS/ZCISe/ZnO NS. Here, excellent performance of ZCISe based ZnO NS photoelectrode is mainly attributed to an intrinsic defect state-related donor–acceptor pair (DAP) in ZCISe QDs with long-lived photogenerated carriers. Photocatalytic properties of Mn–CdS/ZCISe/ZnO NS were evaluated by removing azo dyes with an efficiency of 83%, an enhancement of 97% compared to that of ZnO NS.

MnGa and (Mn,Ga)N-like alloy formation during annealing of Mn/GaN(0001) interface

In this paper the behaviour of the Mn/GaN system under the influence of annealing is presented. The interface is formed by Mn vapour deposition onto the GaN crystal, (0001)-oriented, non-doped under ultrahigh vacuum. Physicochemical properties and structural changes of the interface induced by annealing are investigated in situ by employing X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction (LEED). The impact of annealing on the subsurface layer morphology is observed. Annealing effects, which have been confirmed by XPS and UPS, demonstrate Ga diffusion into the Mn film and Mn dissolution in the bulk GaN. LEED patterns confirm MnGa alloy formation, which in the plane parallel to the substrate surface is arranged in a square lattice with lattice constant equal to about 3.9 Å, and exists in epitaxial configuration relative to the substrate. Incorporation of Mn atoms into the GaN lattice results in the creation of (Mn,Ga)N-like alloy.

A Study on the Characteristics of Cu–Mn–Dy Alloy Resistive Thin Films

Cu–Mn–Dy resistive thin films were prepared on glass and Al2O3 substrates, which was achieved by co-sputtering the Cu–Mn alloy and dysprosium targets. The effects of the addition of dysprosium on the electrical properties and microstructures of annealed Cu–Mn alloy films were investigated. The composition, microstructural and phase evolution of Cu–Mn–Dy films were characterized using field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. All Cu–Mn–Dy films showed an amorphous structure when the annealing temperature was set at 300 °C. After the annealing temperature was increased to 350 °C, the MnO and Cu phases had a significant presence in the Cu–Mn films. However, no MnO phases were observed in Cu–Mn–Dy films at 350 °C. Even Cu–Mn–Dy films annealed at 450 °C showed no MnO phases. This is because Dy addition can suppress MnO formation. Cu–Mn alloy films with 40% dysprosium addition that were annealed at 300 °C exhibited a higher resistivity of ~2100 μΩ·cm with a temperature coefficient of resistance of –85 ppm/°C.

Nonlinear optical and optical power limiting studies of Zn1-xMnxO thin films prepared by spray pyrolysis

Zn1-xMnxO (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) thin films were deposited at 723 K temperature on glass substrate using a solution of molarity of 0.0125 M through spray pyrolysis method. X-ray diffractogram (XRD) analysis confirmed that all the films have (0 0 2) as a preferential orientation with hexagonal wurtzite structure. The increase of dopant marginally changed the crystallite size and lattice parameters. Surface morphology changes fibrous to spherical structure with an increase in doping. X-ray photoelectron spectroscope (XPS) measurements proved the occurrence of manganese is in the Mn2+ transition state along with Oxygen and Zinc content. The films showed ˜90-80% transmittance in the visible region with increasing in Mn concentration. The energy band-gap reduced with increase in dopant, due to sp-d exchange interactions. The nonlinear optical (NLO) properties were studied using z-scan technique under continuous wave (CW) diode pumped solid-state (DPSS) laser operating at 532 nm wavelength. Reverse saturable absorption (RSA) behaviors observed in both undoped and Mn doped films which is attributed to two-photon absorption (TPA) process. The optical limiting properties were also studied, which suggests that the prepared thin films could be used as optical limiters in the visible region.

Topological Hall effect in thin films of Mn1.5PtSn

Spin chirality in metallic materials with non-coplanar magnetic order can give rise to a Berry phase induced topological Hall effect. Here, we report the observation of a large topological Hall effect in high-quality films of Mn$_{1.5}$PtSn that were grown by means of magnetron sputtering on MgO(001). The topological Hall resistivity is present up to $\mu_{0}H \approx 4~$T below the spin reorientation transition temperature, $T_{s}=185$~K. We find, that the maximum topological Hall resistivity is of comparable magnitude as the anomalous Hall resistivity. Owing to the size, the topological Hall effect is directly evident prior to the customarily performed subtraction of magnetometry data. Further, we underline the robustness of the topological Hall effect in Mn\textsubscript{2-x}PtSn by extracting the effect for multiple stoichiometries (x~=~0.5, 0.25, 0.1) and film thicknesses (t = 104, 52, 35~nm) with maximum topological Hall resistivities between $0.76~\mu\Omega$cm and $1.55~\mu\Omega$cm at 150~K.

Influence of the Magnetic Anisotropy Dispersion in Ge3Mn5 Clusters on the Temperature Dependences of Magnetization in Thin Ge:Mn Films

The temperature dependences of magnetization M(T) of thin ion-implanted Ge:Mn (4 at % Mn) films containing Ge3Mn5 clusters were measured on samples cooled in the absence of magnetic field (zero field cooled, ZFC) and in a magnetic field of 10 kOe (field-cooled, FC). It has been established that the shape of ZFC–FC differential M(T) curves is determined by lognormal distribution of the size-dependent magnetic anisotropy energy of Ge3Mn5 clusters. Analysis of the observed ZFC–FC magnetization curves allowed the magnetic anisotropy dispersion (variance) and magnetic anisotropy constant to be estimated.

Nanostructured ZnS : Cu(Mn) Coatings on the Surface of Porous Anodic Alumina for Optical Applications

The results of X-ray diffraction, electron microscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and X-ray photoelectron spectroscopy studies of nanostructured ZnS : Cu(Mn) coatings obtained by ultrahigh vacuum thermal deposition onto the surface of anodic Al2O3 porous matrices are presented. A comparison with data obtained for films on glass substrates is made. Deposition is carried out during the independent evaporation of ZnS powder, metallic Cu, and MnS powder at various temperatures of the evaporation of impurity-ion sources. For the first time, porous nanostructured ZnS : Cu(Mn) films are shown to be formed on the surface of a porous matrix, the structure of which depends on the parameters of the porous structure of the matrices.

Dielectric and Ferroelectric Properties of PZN-4.5PT Nanoparticles Thin Films on Nanostructured Silicon Substrate for Ferrophotovoltaic and Energy Storage Application

The integration of ferroelectric materials as thin films has attracted considerable attention these last years thanks to their outstanding performances that allow considering new features for the realization of photovoltaic devices. Our study focuses on investigating structural, dielectric and ferroelectric properties of undoped and Mn doped PZN-4.5PT nanoparticles thin films on Silicon substrate. We fabricate very stable PZN-4.5PT nanoparticles thin films deposited on nanostructured silicon substrate with giant relative dielectric permittivity of 2.76 × 104 and 17.7 × 104 for respectively the undoped and Mn doped thin films. These values are very large compared to those found in single crystals and might be explained by the influence of the gel in which nanoparticles were dispersed. The SEM images show the crystallization of new hexagonal phases on the film surface probably coming from interaction between Si and the gel. The hysteresis loops permitted to determine the spontaneous polarization (Ps), remnant polarization (Pr) and coercive field Ec which are equal to 11.73 μC/cm2, 10.20 μC/cm2 and 20 V/cm, respectively for the undoped nanoparticles thin film and 22.22 μC/cm2, 19.32 μC/cm2 and 20 V/cm respectively for the Mn doped one. These values are high and correspond to the best ones found in literature compared to typical ferroelectric thin films.

Влияние дисперсии магнитной анизотропии кластеров Ge-=SUB=-3-=/SUB=-Mn-=SUB=-5-=/SUB=- на температурные зависимости намагниченности тонких пленок Ge:Mn

AbstractThe temperature dependences of magnetization M ( T ) of thin ion-implanted Ge:Mn (4 at % Mn) films containing Ge_3Mn_5 clusters were measured on samples cooled in the absence of magnetic field (zero field cooled, ZFC) and in a magnetic field of 10 kOe (field-cooled, FC). It has been established that the shape of ZFC–FC differential M ( T ) curves is determined by lognormal distribution of the size-dependent magnetic anisotropy energy of Ge_3Mn_5 clusters. Analysis of the observed ZFC–FC magnetization curves allowed the magnetic anisotropy dispersion (variance) and magnetic anisotropy constant to be estimated.

Magnetocrystalline anisotropy and exchange probed by high-field anomalous Hall effect in fully compensated half-metallic Mn2RuxGa thin films

Magnetotransport is investigated in thin films of the half-metallic ferrimagnet Mn$_2$Ru$_x$Ga in pulsed magnetic fields of up to 58 T. A non-vanishing Hall signal is observed over a broad temperature range, spanning the compensation temperature 155 K, where the net magnetic moment is strictly zero, the anomalous Hall conductivity is 6673 $\Omega^{-1}.m^{-1}$ and the coercivity exceeds 9 T. Molecular field modelling is used to determine the intra- and inter-sublattice exchange constants and from the spin-flop transition we infer the anisotropy of the electrically active sublattice to be 216 kJ/m$^3$ and predict the magnetic resonances frequencies. Exchange and anisotropy are comparable and hard-axis applied magnetic fields result in a tilting of the magnetic moments from their collinear ground state. Our analysis is applicable to collinear ferrimagnetic half-metal systems.

Solid-state synthesis and characterization of ferromagnetic Mn5Ge3 nanoclusters in GeO/Mn thin films

Mn5Ge3 films are promising materials for spintronic applications due to their high spin polarization and a Curie temperature above room temperature. However, non-magnetic elements such as oxygen, carbon and nitrogen may unpredictably change the structural and magnetic properties of Mn5Ge3 films. Here, we use the solid-state reaction between Mn and GeO thin films to describe the synthesis and the structural and magnetic characterization of Mn5Ge3(Mn5Ge3Oy)-GeO2(GeOx) nanocomposite materials. Our results show that the synthesis of these nanocomposites starts at 180°С when the GeO decomposes into elemental germanium and oxygen and the resulting Ge atoms immediately migrate into the Mn layer to form ferromagnetic Mn5Ge3 nanoclusters. At the same time the oxygen atoms take part in the synthesis of GeOx and GeO2 oxides and also migrate into the Mn5Ge3 lattice to form Mn5Ge3Oy Nowotny nanoclusters. Magnetic analysis assumes the general nature of the Curie temperature increase in carbon-doped Mn5Ge3Cx and Mn5Ge3Oy films. Our findings prove that not only carbon, but oxygen may contribute to the increase of the saturation magnetization and Curie temperature of Mn5Ge3-based nanostructures.

Probing the magnetic properties of ultrathin Pt/Mn bilayers

We report on the interplay between surface morphology and the magnetic properties of Pt/Mn ultra-thin bilayers by measuring the temperature dependence of the resistivity of Hall bars cooled under application of an external magnetic field. The resistivity (ρ) versus temperature (T) curves measured under a magnetic field applied along the x-, y- and z- directions exhibit a clear difference between the zero-field-cooled (ZFC) and field-cooled (FC) traces. The disparity between the ZFC and FC traces allowed us to determine the direction of the magnetic easy-axis. The ρ vs. T characteristic of the Pt/Mn bilayers revealed the existence of antiferromagnetic (AF) order below 79 K, in agreement with the Néel temperature observed in temperature dependent susceptibility curves. We also investigated the morphological evolution of the Mn films as a function of Mn thickness by atomic force microscopy (AFM). We observed the formation of a Mn layered structure on a 2nm-thick Al2O3 buffer layer for films thicker than 2.5 nm. Our results suggest that bilayer structures consisting of non-magnetic noble metals on ultra-thin antiferromagnetic metals can be used as a probe to explore the complex magnetic properties of the AF layer.

Tailoring the visible emissions in ZnS:Mn films for white light generation

Abstract This paper reports the effect of manganese incorporation on the structural, optical and luminescence properties of the as-deposited ZnS films prepared by RF magnetron sputtering process. Mn act as a nucleation centre for the growth of highly crystalline defect free ZnS films with mixed cubic and hexagonal phases. The +2 valence state of Mn ions in ZnS lattice is confirmed by the XPS analysis. An absorption band due to d-d transition of Mn2+ ions is visible in the absorption spectra of ZnS film with highest Mn doping concentration. ZnS:Mn films present an intense orange emission along with the host emissions of ZnS. Optimum Mn content for superior orange emission from ZnS:Mn films is found to be 3 wt %. Origin of orange photoluminescence emission due to the incorporation of Mn2+ in Zn2+ host lattice and its quenching due to cross-relaxation mechanism in the films with higher Mn doping concentration is discussed in detail. We report the possibility of one-step generation of white light emission from the as-synthesized ZnS:Mn films by the adequate tailoring of ZnS host emissions in the blue and green regions (445 nm and 530 nm respectively) and Mn related emission in the orange region (585 nm) employing only one excitation wavelength by suitably tuning the Mn doping concentrations. PL decay of the orange emission is monitored to explore the luminescence mechanism and lifetime of the emission.

Improved white light emission from ZnS:Mn/ZnO/GaN core-shell nanorods array

By depositing ZnS:Mn films using PLD technique to coat ZnO nanorods which were grown on GaN substrate using hydrothermal method, high quality ZnS:Mn/ZnO/GaN core-shell nanorods array was prepared. The PL spectrum of ZnS:Mn/ZnO/GaN core-shell array ranges from blue-violet light to red light (400–700 nm). It consists of four luminous bands: UV light at 375 nm originating from the free exciton emission of ZnO, a blue light emission at 450 nm from GaN, an orange light emission at 590 nm mainly from ZnO nanorods and Mn2+ in ZnS, and a green light emission at about 530 nm related to ZnS:Mn/ZnO interface. The mechanism of green light emission is analyzed in detail. The color coordinate of ZnS:Mn/ZnO/GaN core-shell array is (0.3347, 0.318), and the color temperature is 5375 K, much closer to the standard white light when compared with other systems.

The Growth and Crystalline Structure of Ultrathin Mn Films on Ni(111)

The growth and crystalline structure of ultrathin Mn films are studied in terms of thickness and temperature by scanning tunneling microscopy (STM) as well as medium‐ and low‐energy electron diffraction. We show that the Mn films deposited at room temperature exhibit a thickness‐dependent growth behavior with a layer‐by‐layer growth mode up to 5.3 monolayers. Two transitions in the growth mode can be observed in this range. Atomically resolved STM images of a submonolayer of Mn on Ni(111) reveal a lateral lattice distortion which becomes less significant after the islands form a wetting layer at room temperature. The low‐temperature‐deposited wetting layer shows a metastable lattice distortion which vanishes after annealing to room or higher temperatures. This phenomenon may be attributed to a temperature‐dependent metastable arrangement of the Mn adlayer as well as the distinct interaction strength between Mn–Mn and Mn–Ni atoms. Low‐temperature‐grown thick Mn films exhibit a Stranski–Krastanov growth mode with a stable 30° reconstruction, which remains stable up to room temperature.

ZnO-Based Schottky and Oxide Multilayer Devices for Visibly Transparent Photovoltaic Applications

Autonomous smart windows may be integrated with a stack of active components, such as electrochromic devices, to modulate the opacity/transparency by an applied voltage. This voltage may be generated with a visibly transparent photovoltaic device. This paper describes the processing and performance of zinc oxide (ZnO) films for integration with electrochromic stacks. Sputtered ZnO (2% Mn) films on indium–tin oxide with transparency in the visible range were used to fabricate metal–semiconductor (MS), metal–insulator–semiconductor, and p-i-n heterojunction devices, and their photovoltaic conversion under ultraviolet (UV) illumination was evaluated with and without oxygen plasma-treated surface electrodes (Au, Ag, Al, and Ti/Ag). The MS Schottky parameters were fit against the generalized Bardeen model to obtain the density of interface states ( ${D}_{\textsf {it}} \approx \textsf {8.0}\times \textsf {10}^{\textsf {11}}$ eV−1cm−2) and neutral level ( ${E}_{o} \approx -\textsf {5.2}$ eV). These devices have exhibited a photoconductive behavior at $\lambda = \textsf {365}$ nm, and low-noise Ag-ZnO detectors have exhibited the responsivity ( ${R}$ ) and photoconductive gain ( ${G}$ ) of $\textsf {1.93}\times \textsf {10}^{-\textsf {4}}$ A/W and $\textsf {6.57}\times \textsf {10}^{-\textsf {4}}$ , respectively. Confirmed via matched-pair analysis, postmetallization oxygen plasma treatment of Ag and Ti/Ag electrodes has resulted in increased Schottky barrier heights, which maximized with a 2-nm SiO2 electron blocking layer, coupled with the suppression of recombination at the MS interface and blocking of majority carriers. For interdigitated devices under monochromatic UV-C illumination, the open-circuit voltage ( ${V}_{\textsf {oc}}$ ) was 1.2 V and short-circuit current density ( ${J}_{\textsf {sc}}$ ), due to minority carrier tunneling, was 0.68 mA/cm2.

Modulated electrical and magnetic properties of Mn thin film by structural deformation of BaTiO3

A ferrimagnetic ordering with a magnetic moment of 0.66 μB/Mn has been obtained in an epitaxial Mn thin film on a BaTiO3 substrate. The structural deformation of the Mn film was modulated by thermal strain due to the thermal expansion difference between the Mn film and BaTiO3. Three jumps in the resistivity at 185, 290, and 390 K and two jumps in the magnetization at 290 and 365 K in the Mn film correspond to structural phase transitions of BaTiO3 at below 400 K. These results indicate the feasibility of tuning the electrical and magnetic properties of the Mn film by modulating the interface strain via phase changes of BaTiO3.

Analysis of optical dispersion parameters and electrochromic properties of manganese-doped Co3O4 dendrite structured thin films

Nebulized spray pyrolysis method was employed to deposit pristine and manganese (Mn) -doped Co3O4 thin films for different Mn concentrations (4, 6 and 8 at.%). The structural properties revealed that the obtained films show predominant orientation along (311) plane and significant peak shift was observed upon an increase in Mn doping confirms the substitution of Mn in Co3O4 lattice. The pristine Co3O4 film shows clustered grains and dendrite patterns appearing with the increase in Mn content as evident from SEM studies. The optical dispersion parameters of the prepared films of pristine and Mn doped Co3O4 films were determined from UV transmission spectra. The phase purity and elemental analysis of the films revealed single phase with better stoichiometric films were obtained. The XPS core level spectra of 6 at.% Mn doped Co3O4 films exhibited the presence of two different oxidation states (Mn2+ and Mn3+). The electrical resistivity of the films decreased with increase in Mn dopant concentration was observed from linear four probe method. The Co3O4 film deposited using 6 at.% of Mn exhibited a maximum optical modulation of 35% and coloration efficiency of 29 cm2/C.