High enhanced magnetization in carbon-doped Mn3Ga thin films

Carbon-doped Mn₃Ga thin films were grown on Si/SiO₂ substrates using rf magnetron sputtering technique. The tetragonal D0₂₂–type crystalline structure of ferrimagnetic Mn₃Ga is preserved on the Mn₃GaC_x films upon carbon concentrations up to x = 0.5, whereas higher concentrations lead to the formation of the antiperovskite Mn₃GaC phase. Geometry optimization calculations using the density functional theory were performed on a 2 × 2 × 2 Mn₃GaC_0.25 supercell with C in different positions in order to find that the most stable position for the C is interstitial octahedral site. Magnetic M(H) loops show that saturation magnetization M_s of Mn₃GaC_0.25 is enhanced to 200 kAm⁻¹ (from M_s = 90 kAm⁻¹ for undoped films). The increase of the C concentration leads to a reduction of the Curie temperature from 770 K to ∼420 K at the same time that the lattice cell suffers an expansion. The enhancement of M_s is explained in terms of a 90° ferromagnetic superexchange Mn-C-Mn interaction.     

Structure, magnetization, and magnetostriction of Sm-R-Fe （R = Pr, Nd） thin films

The structure, magnetization, and magnetostriction of Sm0.9Pr0.1Fex and Sm1-xNdxFel.9 thin films have been investigated using X-ray diffraction, vibrating sample magnetometer, and optical cantilever method. It is found that the structure of Sm0.9Pr0.1Fex thin films consists of an Sm-Pr-Fe amorphous phase when x≤2.69 and that of Sm1-xNdxFel.9 thin films consists of an Sm-Nd-Fe amorphous phase. The in-plane magnetization of Sm0.91Pr0.1Fex thin films increases with increase in the Fe content, and low values of the in-plane coercivity occur in the range of 1.62≤ x≤ 2.28. The magnetostriction value of Sm0.91Pr0.1Fex thin films increases with increasing the Fe content when x ≤ 1.94 and decreases when x 〉 1.94. The in-plane magnetostriction of Sm1-xNdxFe1.9 thin films under low magnetic fields has been improved by the substitution of Nd for Sm when x = 0.2.     

Structure and electrical properties of PbZrO3 antiferroelectric thin films doped with barium and strontium

In this paper, we report on the structure and electrical properties of lead zirconate (PbZrO₃) thin films doped with barium (Ba²⁺) and strontium (Sr²⁺) deposited on platinum-buffered silicon substrates by a sol-gel method. Effects of Ba²⁺ and Sr²⁺ dopants on microstructure and electrical properties of the PbZrO₃ antiferroelectric thin films were investigated in details. X-ray diffraction patterns and scanning electron microscope micrographs illustrated that orientation and surface microstructure of these antiferroelectric films were dopant-dependent. The dielectric measurements showed that Sr²⁺ doping stabilized the antiferroelectric phase, while Ba²⁺ doping destabilized the antiferroelectric phase. It was also found that fatigue property of the antiferroelectric PbZrO₃ thin films was improved remarkably by the dopants.     

Controlled biaxial deformation of nanostructured W/Cu thin films studied by X-ray diffraction

The deformation behaviour of 150 nm thick W/Cu nanocomposite deposited on polyimide substrates has been analysed under equi-biaxial tensile testing coupled to X-ray diffraction technique. The experiments were carried out using a biaxial device that has been developed for the DiffAbs beamline of SOLEIL synchrotron source. Finite element analysis has been performed to study the strain distribution into the cruciform shape substrate and define the homogeneous deformed volume. X-ray measured elastic strains in tungsten sub-layers could be carried out for both principal directions. The strain field was determined to be almost equi-biaxial as expected and compared to finite element calculations.     

Annealing effects on microstructure and properties of Ta-Al thin film resistors

The Ta-Al thin film resistor has been used as a heating element of the thermal bubble inkjet printhead with several millions of thermal cycle operations between room temperature and about 350 °C. In this paper, the thermal stability of Ta-Al alloy films was investigated by the variation of phase transformation, microstructure and resistivity at annealing temperatures of 450-650 °C for 1 h. Three kinds of Ta-Al films were prepared with average Ta/Al atomic composition ratios of about 2/1, 1/1 and 1/2, respectively. The Ta-Al film with composition ratio of about 1/1 exhibits amorphous-like microstructure with nanocrystalline grains embedded in an amorphous matrix. The thermal stability is strongly related to the composition and microstructure in Ta-Al alloy. The best thermal stability of Ta-Al films occurs in Ta-rich alloy up to 650 °C and the worst occurs in Al-rich alloy with phase transformation as low as 450 °C. The amorphous-like Ta-Al alloy is stable up to 550 °C, but then exhibits polycrystalline multiphase formation at 650 °C. The resistivity of Ta-Al films is also related to the annealing temperature. The resistivity of Ta-rich Ta-Al film increases to about 13.5% from as-deposited to after annealing at 450 °C while that is doubled in the Al-rich Ta-Al film. In contrast, the resistivity of the amorphous-like Ta-Al film increased by about 6.1% at 450 °C and then remains nearly stable at 1.5% variation on annealing at 450-550 °C. The as-deposited amorphous-like Ta-Al film has the merits of high resistivity, smooth morphology and good thermal stability at annealing temperatures of up to 550 °C. These attributes are beneficial for the thermal bubble inkjet application with thermal cycling at maximum temperatures below 400 °C.     

Nano-grain Al2O3 crystals grown by sputtering of aluminium on CoCrPt thin films for potential application in ultra-high-density recording media

Designing supraceramic assemblies based on Al₂O₃ has remained a challenge due to the problems associated with the suitable dispersion in neat compounds and ability to control the preferred orientation in a unique fashion. Herein, granular HCP-(CoCrPt)_100−X(Al₂O₃)_X (X represents the percent weight) thin films with Si(1 0 0) substrates have been fabricated using sputtering technique followed by annealing treatment. Structural and magnetic properties of thin film have been investigated for potential application in magnetic recording media. It was shown that coercivity increased from 0.5 to 2.5 kOe by increasing the nano-grain Al₂O₃ content in the CoCrPt magnetic layers. In CoCrPt-Al₂O₃ thin films coercivity of 2.5 kOe has been obtained with increasing the Al₂O₃ content from 3 to 13 wt.% in the annealed thin films. The structural properties of the samples were studied using X-ray diffraction (XRD) and transmission electron microscope (TEM) equipped with selected area electron diffraction (SAED). The magnetic properties of the samples were measured with a vibrating sample magnetometer (VSM). The VSM results showed that the HCP-CoCrPt-Al₂O₃ granular films are a promising candidate for ultra-high-density recording media because of its low Al₂O₃ content and simple manufacturing process.     

Microstructure and thickness dependent magnetic properties of nanogranular Co-Zn-O thin films for microwave applications

Co-based granular thin films with in-plane anisotropy were deposited on Si substrate by magnetron sputtering. The films have a phase structure of Co nanocrystallites and amorphous Zn-O inter-granular phases. The Co nanograins with uniform size of 8-10 nm are evenly distributed in the amorphous matrix. This structure gives the films relatively high resistivities. The as-deposited films with thickness larger than 100 nm have low coercivity (<10 Oe) along both easy and hard directions. The dynamic properties in the frequency range up 5 GHz for the films with various thicknesses have been investigated. High values of permeability (μ′ up to 560 and μ″ up to 1000) and ferromagnetic resonance frequency (FMR) up to 4.1 GHz have been obtained in these films. The FMR frequency decreases with increasing thickness, because of the increases in real and imaginary permeabilities. The high frequency characteristics have complicated dependences on the resistivity, anisotropy field, and magnetization. The microwave properties of Co-Zn-O films can be adjusted in a relatively wide range by changing film thickness, which makes these films promising for absorber applications.     

Characteristic evaluation on spray-deposited WFTO thin films as a function of W doping ratio

In this work, F and F+W simultaneously doped SnO2 highly transparent conducting thin films were deposited on glass substrates at(500 ± 5) °C temperature by the spray pyrolysis method. Microstructural, morphological,electrical and optical properties of FTO films were investigated as a function of tungsten(W) doping, in the range from0 to 5 at%. X-ray diffraction patterns show that the films exhibit a tetragonal cassiterite structure and(200) preferential orientation of FTO film, and the relative strength of these peaks changes with altering the W doping ratio. The preferred growth of(211) changed to(200) plane with 2 at% W doping level and 3 at% W-doped film had(200) orientation and with further doping, this changed to(110) orientation.The scanning electron microscopy and atomic force microscopy images of the films indicate that the films are made up of dense small particles of a pyramidal shape and have a smooth surface. It was observed that the surface morphology of the films did not change much when the W element was inserted to the FTO structure. It was found that the sheet resistance values of the films varied with W doping ratio, and 2 at% W-doped FTO thin film exhibited the lowest values of sheet resistance(1.12 X). Also, the highest figure of merit, infrared reflectivity and optical band gap values were calculated for 2 at% W-doped FTO film as 50.9 9 10-2X-1,98.82 % and 4.13 eV, respectively. These results make the films an effective candidate for usage in many optoelectronic applications and photo-thermal conversion of solar energy.     

Growth of CdS thin films and nanowires for flexible photoelectrochemical cells

In this study, cadmium sulfide (CdS) nanocrystal thin films and nanowires have been deposited onto mechanically flexible substrates via dc-electrodeposition, which is a very suitable technique for large area manufacturing. For the first time with this study, flexible CdS nanocrystal thin films were integrated into photoelectrochemical (PEC) cells and their performances were compared with CdS nanowires. It has been demonstrated that PEC performance of both nanocrystal thin films and nanowires were a strong function of production conditions such as deposition time and voltage. The maximum power conversion efficiency of the CdS nanocrystal thin films obtained in this study was 0.3%. On the other hand, higher efficiencies (about 1.4%) were observed for the CdS nanowires. UV-vis analysis confirmed that both transmittance and band gap energies of the CdS nanowires were lower than that of CdS nanocrystal thin films. X-ray diffraction analysis revealed that both nanocrystal thin films and nanowires have a preferred orientation at 26° (2θ), which can be attributed to the CdS (0 0 2) structure.     

Structural and magnetic characterization of martensitic Ni–Mn–Ga thin films deposited on Mo foil

Three martensitic Ni_51.4Mn_28.3Ga_20.3 thin films sputter-deposited on a Mo foil were investigated with regard to their crystal and magnetic domain structures, as well as their magnetic and magnetostrain properties. The film thicknesses, d, were 0.1, 0.4 and 1.0μm. X-ray and electron diffraction patterns revealed a tetragonal modulated martensitic phase (10 M) in the films. The surface topography and micromagnetic structure were studied by scanning probe microscopy. A maze magnetic domain structure featuring a large out-of-plane magnetization component was found in all films. The domain width, δ, depends on the film thickness as . The thickness dependencies of the saturation magnetization, saturation magnetic field and magnetic anisotropy were clarified. Beam cantilever tests on the Ni–Mn–Ga/Mo composite as a function of magnetic field showed reversible strains, which are larger than ordinary magnetostriction.     

Low temperature processed highly conducting, transparent, and wide bandgap Gd doped CdO thin films for transparent electronics

Gadolinium (Gd) doped cadmium oxide (CdO) thin films are grown at low temperature (100 °C) using pulsed laser deposition technique. The effect of oxygen partial pressures on structural, optical, and electrical properties is studied. X-ray diffraction studies reveal that these films are polycrystalline in nature with preferred orientation along (1 1 1) direction. Atomic force microscopy studies show that these films are very smooth with maximum root mean square roughness of 0.77 nm. These films are highly transparent and transparency of the films increases with increase in oxygen partial pressure. We observe an increase in optical bandgap of CdO films by Gd doping. The maximum optical band gap of 3.4 eV is observed for films grown at 1 × 10⁻⁵ mbar. The electrical resistivity of the films first decreases and then increases with increase in oxygen partial pressure. The lowest electrical resistivity of 2.71 × 10⁻⁵ Ω cm and highest mobility of 258 cm²/Vs is observed. These low temperature processed highly conducting, transparent, and wide bandgap semiconducting films could be used for flexible optoelectronic applications.     

Structural characteristics and optical properties of plasma assisted reactive magnetron sputtered dielectric thin films for planar waveguiding applications

Thin films of aluminum oxide (Al₂O₃), tantalum pentoxide (Ta₂O₅), titanium oxide (TiO₂), yttrium oxide (Y₂O₃) and zirconium oxide (ZrO₂) were deposited by plasma assisted reactive dual magnetron sputtering to determine their suitability as a host for a rare earth doped planar waveguide upconversion laser. The effect of deposition parameters such as cathode, plasma power and oxygen gas flows were studied and the operational working points were determined. Both power and lambda control were used to optimize the optical quality of each material. By using lambda control feedback system, the magnetron power fluctuates to sustain a fixed oxygen flow in the target area reducing the compound layer growth on the material and maintaining a healthy deposition rate. The optical properties, structure and crystalline phase of each film were found to be dependent on the process parameters. X-ray diffraction (XRD) analysis revealed that the thin films varied from amorphous to highly crystalline depending on the deposition conditions. X-ray photoelectron spectroscopy (XPS) was utilized for surface compositional analysis revealing that films had varying stoichiometric ratios which are controlled for each material by the deposition parameters chosen. The waveguide loss for the thin film layers was investigated and Ta₂O₅ was shown to have a slab waveguide loss of ~ 1 dB/cm at both visible and infra-red wavelengths making it ideal for planar waveguide and laser applications. TiO₂, Y₂O₃ and ZrO₂ were found to deposit in a highly crystalline phase. Waveguiding in the TiO₂ layers was not possible at 633 nm or in the infrared region. The Y₂O₃ samples gave low loss (2–4 dB/cm) at the 1.3 and 1.5 μm wavelengths but no waveguiding at 633 nm or 833 nm was possible. Atomic force microscopy showed rough surface topography for TiO₂, Y₂O₃ and ZrO₂ akin to their crystalline growth with the SEM images confirming the regular crystalline columnar structure for the case of Y₂O₃ and ZrO₂.     

Improved design of inverted magnetrons used for deposition of thin films on wires

The inverted type of cylindrical magnetron sputtering has not been widely used, although this system is useful for only certain types of applications such as fibre coatings. This paper presents two types of electrode configurations which improved the complicancy of target assembly by using positive voltage power supply. One is a simple type which has no endplate (type I), and the other is a modified type which has a target constructed with a large cylindrical part, a conical part and a small cylindrical part (type II). When positive voltage was applied to an anode for both types, a stable glow discharge was established and a high deposition rate was obtained. The substrate bias current was monitored to estimate the effect of ion bombardment. As a result, it was found that the substrate current was larger in type II than in type I. Microstructure and morphology of titanium films deposited on thin wires were investigated by scanning electron microscopy in relation to preparation conditions. High level ion bombardment was found to be effective in obtaiing a good adhesion for wire coatings.     

CuS-based thin films for architectural glazing applications produced by co-evaporation: Morphology, optical and electrical properties

Copper sulphide thin films in the 90–300 nm thickness range have been deposited on soda–lime glass substrates by thermal co-evaporation of Cu and S. Depending on the film thickness, the optical transmittance in the visible region is of about 50% for the thinnest film and 19% for the thickest film, with the corresponding near-infrared transmittance dropping from 11% to near-zero at 2500 nm as the film thickness increases from 90 to 300 nm. A resistivity of ρ ~ 10^− 4 Ω cm has been obtained for the films. The optoelectronic properties of the films remained practically unchanged after one year stored under laboratory ambient. The optical properties obtained for selected CuS-based films make them suitable for their use as effective solar control glazings in warm climates.     

Substrates effect on Zn1−xMnxO thin films grown by RF magnetron sputtering

In this paper, we have presented the surface effect of the substrates on Mn doped ZnO (Zn_1−xMn_xO) thin films grown on Si(1 0 0) and sapphire [i.e. Al₂O₃(0 0 0 1)] by RF magnetron sputtering. These grown films have been characterized by X-ray diffraction (XRD), photoluminescence (PL) and vibrating sample magnetometer (VSM) to know its structural, optical and magnetic properties. All these properties have been found to be strongly influenced by the substrate surface on which the films have been deposited. The XRD results show that the Mn doped ZnO films deposited on Si(1 0 0) exhibit a polycrystalline nature whereas the films on sapphire substrate have only (0 0 2) preferential orientations indicating that the films are single crystalline. The studies of room temperature PL spectra reveal that the Zn_1−xMn_xO/Si(1 0 0) system is under severe compressive strain while the strain is almost relaxed in Zn_1−xMn_xO/Al₂O₃(0 0 0 1) system. It has been observed from VSM studies that Zn_1−xMn_xO/Al₂O₃(0 0 0 1) system shows ferromagnetic nature while the paramagnetic behaviour observed in Zn_1−xMn_xO/Si(1 0 0) system.     

Effect of V doping on phase composition and electrical properties of K0.4Na0.6Nb1−xVxO3 thin films

Lead-free K_0.4Na_0.6Nb_1−xV_xO₃ thin films were prepared by chemical solution deposition method. The effects of V doping on the phase composition and electrical properties of the films were studied at room temperature. The results indicate that the films are composed of orthorhombic and tetragonal phases, and the phase composition is affected by V content. It is also found that the ferroelectric and dielectric properties are improved by V doping (2P_rmax = 35.5 μC/cm, ?_max = 1189). The enhanced electrical properties are attributed to the more T-phase content and better quality of K_0.4Na_0.6Nb_1−xV_xO₃ (x = 0.015) film.     

Deposition and characteristics of chromium nitride thin film coatings on precision balls for tribological applications

Thin film hard coatings on rolling element surfaces can enhance the overall wear resistance of rolling element bearings, as demonstrated previously for coated tapered, cylindrical, and spherical roller bearings. Hard coatings in ball bearings are less common because of the difficulty in achieving uniform film thickness on a ball surface. This limitation is overcome by a new process for depositing chromium nitride coatings with uniform thickness on precision balls using ion beam assisted deposition (IBAD) e-beam evaporation. Scanning electron microscopy indicated that the deposited films were smooth and conformal on the ball surfaces with no areas of localized delamination. Auger electron spectroscopy confirmed that Cr₂N and CrN bulk film stoichiometry was achievable by modulating the argon to nitrogen process gas ratio during deposition. Transmission electron microscopy revealed dense, polycrystalline film structure. Film hardness and elastic modulus as measured using nanoindentation on the coated balls met expectations for chromium nitride, and tribological testing of the coated balls in angular contact ball bearings under moderate contact stress levels demonstrated adequate film adhesion for practical use of these coatings in bearing applications.     

Growth of conformal copper films on TaN by electrochemical deposition for ULSI interconnects

Seedless copper electrochemical deposition (ECD) becomes a potential interconnect technology while device dimension keeps shrinking in ULSI design. In seedless copper ECD on TaN, which is a widely used diffusion barrier, uniform growth of copper film on TaN is hindered because a robust native Ta₂O₅ exists on TaN surface. Complete removal of the native Ta₂O₅ can be attained using a saturated KOH solution that is assisted by an anodic voltage. This then permits that copper film grows on the pretreated TaN surface in a copper-citrate (Cu-Cit) complex electrolyte. Its growing morphology and deposition rate are dependent on the etching depth of as-deposited TaN in the KOH solution. Even for a very short etching time of 0.8 s, thin Ta₂O₅ is totally etched off and the activated TaN surface appears. Thin and conformal copper films grown in a layer-by-layer mode on the TaN surface are proper to function as an ECD seed or metal lines for ULSI interconnects.     

Synthesis of layered birnessite-type manganese oxide thin films on plastic substrates by chemical bath deposition for flexible transparent supercapacitors

Layered birnessite-type manganese oxide thin films are successfully fabricated on indium tin oxide coated polyethylene terephthalate substrates for flexible transparent supercapacitors by a facile, effective and inexpensive chemical bath deposition technology from an alkaline KMnO₄ aqueous solution at room temperature. The effects of deposition conditions, including KMnO₄ concentration, initial molar ratio of NH₃·H₂O and KMnO₄, bath temperature, and reaction time, on the electrochemical properties of MnO₂ thin films are investigated. Layered birnessite-type MnO₂ thin films deposited under optimum conditions display three-dimensional porous morphology, high hydrophilicity, and a transmittance of 77.4% at 550 nm. A special capacitance of 229.2 F g⁻¹ and a capacitance retention ratio of 83% are obtained from the films after 1000 cycles at 10 mV s⁻¹ in 1 M Na₂SO₄. Compressive and tensile bending tests show that as-prepared MnO₂ thin film electrodes possess excellent mechanical flexibility and electrochemical stability.