Improvement of magnetic characteristics and electrical properties of FeCoHfO/AlOx multilayered films

High permeability magnetic films can enhance the inductance of thin-film inductors in DC-DC converters. In order to obtain high permeability, effective uniaxial anisotropic field should be as low as possible. A multilayered technique (laminating the magnetic layers with oxide spacers) was exploited to improve the magnetic properties of thick films. The FeCoHfO/AlO_x multilayered films were fabricated by dc reactive magnetron sputtering. Inserting an insulator (AlO_x) layer can decrease the magneto-elastic anisotropy by reducing the residual stress of the FeCoHfO magnetic films. The anisotropic field and resistivity of the FeCoHfO/AlO_x multilayered films were evidently improved by multilayered coating. With this optimum configuration of 9 layers structure [FeCoHfO (133 nm)/AlO_x (10 nm)]₉, low anisotropic field (H_K = 65 Oe) and high resistivity (ρ ∼ 1350) μΩ cm were achieved.     

Effects of the stacking levels on permeability characteristics and soft magnetic properties in FeCoHfAlO/AlOx multilayered films

In the communication industry, miniaturization is highly required for inductor devices. In order to miniature the dimension of inductors, high inductance is necessary. For this purpose, to employ high-permeability magnetic films enhances the inductance of inductors. For high-permeability, in-plane uniaxial anisotropy is a critical demand. The FeCoHfAlO/AlO_x multilayered films were fabricated by dc reactive magnetron sputtering. Due to the insertion of AlO_x layers, the out-of-plane uniaxial anisotropy of the FeCoHfAlO magnetic films is reduced and their resistivity is also raised. Therefore, the permeability of the FeCoHfAlO/AlO_x multilayers will be increased further. With the optimum configuration of a seven-layer structure [FeCoHfAlO (171 nm)/AlO_x (10 nm)]₇, high resistivity (ρ ~ 7490 μΩcm) and high-permeability (μ′ > 90 at 30-50 MHz) were obtained. The permeability increased nearly ten times from 9 (3 layers) to 98 (7 layers).     

Deposition and properties of ZrNx films produced by radio frequency reactive magnetron sputtering

Thin ZrN_x films have been prepared by reactive radio frequency magnetron sputtering. The radio frequency power has been chosen as a sputtering parameter and the effect on the compositional and optical properties of the films was systematically studied. The films have been analyzed by X-ray photoelectron spectroscopy. The reflectance and transmittance of the samples have been recorded by a spectrophotometer in the UV-Vis-IR range. The effects of the different powers (in the range 100-400 W) on the stoichiometry of ZrN_x films have been studied. The components revealed on N 1s photoelectron peaks were correlated with different bounding states for the zirconium nitride. The threshold power value between N-rich ZrN_x films and Zr-rich ZrN_x ones is 270 W. A correlation has been observed between the optical properties and the stoichiometry of the films. In fact, the samples catalogued as N-rich by X-ray photoelectron spectroscopy analyses are optically insulating and the Zr-rich ones show a metallic behaviour. A simple growth model has been set up in order to explain the different chemical states detected from the compositional measurements.     

Characterization of Ni0.92V0.08Ox thin films deposited by the pulse sputter method

Based on the use of 8 at.%V-92 at.%Ni alloy target, Ni_0.92V_0.08O_x thin films are deposited via the pulse sputter method to avoid the ferromagnetic disadvantage when using a pure Ni metallic target. Crystallinity, microstructure and electrochromic (EC) properties are investigated systematically by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The optical properties of the Ni_0.92V_0.08O_x films are analyzed by a UV/VIS spectrophotometer (UV–Visible). Electrochromic tests are performed using an electrochemical analyzer. Experimental results indicate that the thickness, chemical composition, microstructure, and electrochromic properties heavily depend on the plasma power and the argon/oxygen ratio. The XPS and XRD analyses reveal that Ni²⁺, Ni³⁺, V⁴⁺ and V⁵⁺ co-exist in the Ni_0.92V_0.08O_x films and form an ideal stoichiometric compound at plasma power above 250 W, demonstrating that V can stabilize the valence state of Ni²⁺. Films deposited at 100 W yields the optimal electrochromic properties, with high optical modulation, high coloration efficiency and the lowest color memory effect at wavelengths of 400, 550 and 800 nm.     

Deposition of amorphous Fe-Zr alloys by magnetron co-sputtering

In the last decades, amorphous metal alloys were under intensive research because of their specific properties. Furthermore, amorphous magnetic metallic alloys, also known as metallic glasses, are important because of their application in electronic industry, information technology, recording media, etc. [Shen J, Kirschner J. Surf. Sci. 2002;500:300-322; Bass J, Pratt Jr WP. Physica 2002;B321:1-8; Dugaev VK, Vygranenko Yu, Vieira M, et. al. Physica 2003;E16:558-562]. Fe_1−xZr_x amorphous films co-condensed by magnetron sputtering were studied. X-ray diffraction methods were applied for studying a glass forming range vs. the composition of the elements. Electrical properties of the samples were measured by so-called four-probe and Van der Pauw methods. The surface morphology was investigated by SEM. The results show that amorphous Fe_1−xZr_x alloys with 1.5 nm crystallites could be synthesized by magnetron co-sputtering on the substrates at room temperature when the alloy's composition was Fe_0.91Zr_0.09 with a very smooth surface. The grain size of alloys decreased increasing the Zr concentration. The resistivity of the thin films of these alloys depends on the crystalline size and structure.     

Magnetic and electronic transport properties of antiperovskite Mn3Cu(Ge)N thin films

The antiperovskite structure Mn₃Cu(Ge)N thin films were grown on single crystal Si (100) substrates by facing target magnetron sputtering. It is found that the films exhibit (100) preferred orientation. Ge-doping does not change the antiperovskite structure but leads to obvious changes in surface morphologies, magnetic and electronic transport properties. As a function of temperature, the resistivity of the films shows a semiconductor-type behavior. Moreover, it is worth noting that an abrupt change of resistivity is observed and magnetic ordering of the films changes from ferrimagnetic (FI) to antiferromagnetic (AFM) due to Ge-doping. In addition, both the transition temperature (T_t) and Néel temperature (T_N) move towards higher temperature with increasing Ge content.     

Optimization of sputtering parameters for deposition of Al-doped ZnO films by rf magnetron sputtering in Ar + H2 ambient at room temperature

The effects of sputtering pressure and power on structural and optical-electrical properties of Al-doped ZnO films were systemically investigated at substrate temperature of room temperature and H₂/(Ar + H₂) flow ratio of 5%. The results show that carrier concentration and mobility of the films show nonmonotone change due to the evolution of microstructure and lattice defect of the films caused by introduction of H₂ with increasing sputtering pressure and power. The transmittance of the films is also found to be related to the introduction of H₂ in addition to usually considered surface roughness and crystallinity. Finally, optimized sputtering pressure and power are 0.8 Pa and 100 W, respectively, and obtained minimum resistivity and highest transmittance are 1.43 × 10^− 3 Ω·cm and 90.5%, respectively. In addition, it is found that E_g of the films is mainly controlled by the carrier concentration, but crystallite size and stress should also be considered for the films deposited at different powers.     

The effect of substrate temperature on the physical properties of tantalum oxide thin films grown by reactive radio-frequency sputtering

Thin films of TaO_x were deposited on Si(1 0 0) by radio-frequency magnetron sputtering at substrate temperatures of 25, 100, 200, 300, 400, and 500 °C. The properties of TaO_x thin films deposited with different oxygen-to-argon gas ratios and substrate temperatures were evaluated. The results show that the films with lowest leakage current density were obtained at ambient temperature with an oxygen mixture ratio (OMR) of 60% and the oxygen-to-tantalum ratio has a minimum with increasing deposition substrate temperature. From the current–voltage (I–V) characteristics of the TaO_x thin films as a function of deposition substrate temperature, we found that the leakage current density in the TaO_x thin films increases with increasing deposition substrate temperature. The higher leakage current density in the TaO_x films is correlated to the oxygen deficiency in TaO_x films and crystallization at higher deposition temperature.     

Sputter deposition of refractory metal silicides from cold-pressed vacuum-sintered targets

Sputter deposition of refractory metal silicides from cold-pressed vacuum-sintered composite targets of TaSi_x, WSi_x, MoSi_x and TiSi_x is a simple and reproducible technique for very-large-scale integrated metallization. The films were deposited in a Varian 3180 sputtering system onto Si(100) wafers and were annealed in a Varian IA-200 rapid isothermal annealer. The resistivity, stress, stoichiometry, microstructure and morphology were studied before and after annealing. Deposition rate and reflectivity data are also included. Data will be presented for films deposited at 2.0 kW. The effects on film quality of varying the substrate temperature and of applying a d.c. bias voltage during deposition are discussed for tantalum and tungsten silicides. The optimum deposition conditions for obtaining the lowest resistivity silicide films (approximately 70 μΩ cm for TaSi_x, 50 μΩ cm for WSi_x, 80 μΩ cm for MoSi_x and 28 μΩ cm for TiSi_x) are with non-biased substrates at ambient temperature.     

Large-distance rf- and dc-sputtering of epitaxial La1 − xSrxMnO3 thin films

Studies on large-distance sputtering as an effective alternative to molecular beam epitaxy, pulsed laser deposition or off-axis sputtering for the deposition of epitaxial La_1 − xSr_xMnO₃ (LSMO) thin films, are reported. The focus of this study is on the quality of the samples and their structural and magnetic properties. The dependence of the characteristics of the LSMO films on the sputtering mode (rf, dc) and the sputtering parameters, in particular on the oxygen partial pressure is established and discussed. It is shown that large-distance sputtering can provide high quality LSMO thin films without the need for post-annealing.     

Effects of the Ta content on the microstructure and electrical property of reactively sputtered TaxZr1−xN thin films

The Ta_xZr_1−xN films were prepared by reactive magnetron sputtering and the concentration of zirconium and tantalum was regulated by controlling the power to the sputtering guns. The effects of the Ta content on the microstructure, composition and electrical properties of Ta_xZr_1−xN films were investigated by x-ray diffraction, field-emission electron probe micro-analyzer, atomic force microscopy, x-ray photoelectron spectroscopy, four point probe and Hall-effect measurements. Results indicated that the Ta_xZr_1−xN films with different Ta contents were crystallized in NaCl-type structure. However, the lattice constant of Ta_xZr_1−xN films decreased with the increase of the Ta content due to the smaller ionic radius of Ta⁵⁺ comparing with that of Zr⁴⁺. The decreasing lattice constant of Ta_xZr_1−xN films with the Ta content evidenced the successful substitution of Zr with Ta. The electrical resistivity of Ta_xZr_1−xN films showed a minimum value of 78 μΩ cm at Ta content of 3.5 at.% and then increased with the increase of Ta content. Hall measurements indicated that the electrical conduction of films was essentially due to electrons (n-type). And the increase of carrier density and mobility at a Ta content of 3.5 at.%, caused by the extra d valence electron of Ta and the less electron scattering of grain boundaries, was responsible for the further decreasing of resistivity from pure ZrN_x films.     

Structure, magnetic and electrical transport properties of (Fe3O4)100 − xPtx composite films

Structure, magnetic and electrical transport properties of the polycrystalline (Fe₃O₄)_100 − xPt_x composite films fabricated using DC reactive magnetron sputtering at ambient temperature were investigated systematically. It is found that the films are composed of inverse-spinel-structured polycrystalline Fe₃O₄ and Pt. Pt addition proves the growth of Fe₃O₄ grains with the (111) orientation. All the films are ferromagnetic at room temperature. The dominant magnetic reversal mechanism turns from domain wall motion to Stoner-Wohlfarth rotation with the increasing x. The electrical transport mechanism also changes with the increasing x because Pt addition decreases the height of the tunneling barrier at the Fe₃O₄ grain boundaries, and makes the magnetoresistance of the films decrease.     

Structural and Electrical Properties of Monovalent Doped Manganites Pr0.6Sr0.4−x K x MnO3 (x=0, 0.05 and 0.1)

Structural and electrical properties of the mixed-valence monovalent doped manganites Pr_0.6Sr_0.4?x K _x MnO₃ (x=0, 0.05 and 0.1), prepared using the conventional solid-state synthesis method, have been investigated. Rietveld refinement of the X-ray diffraction patterns at room temperature shows a slight increase in unit cell volume with K content and confirms that all powder samples are single phase and crystallize in the orthorhombic structure with Pnma space group. Electrical resistivity measurements under and without magnetic field show a transition from the metallic to insulating behavior. The electrical conductivity is improved with increasing K content. The resistivity data in metallic region were fitted according to the electron–electron scattering process while in insulating region they were fitted using the small polaron hopping SPH model and Mott’s variable range hopping VRH model.     

Characterization of titanium silicide films formed by composite sputtering and rapid thermal annealing

Titanium silicide films were prepared by sputtering from a single composite TiSi_x source followed by rapid thermal annealing in N₂. The composition, resistivity, crystal structure and microstructure were investigated using Auger electron spectroscopy, Rutherford backscattering spectrometry, scanning and transmission electron microscopy, X-ray and electron diffraction and a four-point resistivity probe. As-deposited and fully annealed films were found to possess a TiSi_2.2 stoichiometry and to contain 6–7 at.% O and significant amounts of several metallic impurities (copper, iron and tungsten). Rapid thermal annealing at 850–1000°C for 10 s forms a polycrystalline equilibrium orthorhombic phase TiSi₂ structure with 0.25-0.50 μm grains. The annealed layer resistivity was reduced to 28 μΩ cm, i.e. 1.4Ω/▭ for a 0.20 μm film. No expulsion of silicon was observed after annealing, and it appears that excess silicon has trapped oxygen within the film in the form of silicon oxide precipitates. Titanium polycide layers were unable to be etched successfully in an SF₆-CCl₄ plasma because of the presence of the non-volatile copper and iron impurities within the silicide.     

Magnetic properties and microstructures of perpendicular anisotropy (SmCo7/Cu)n films

Pseudobinary SmCo_7 − xCu_x intermetallic compound films with a TbCu₇-type structure were prepared by sputtered (SmCo₇/Cu)_n multilayer. After annealing, the spacer layer Cu (0.5-1.5 nm) diffused into the SmCo₇ matrix and stabilized the SmCo₇ meta-stable phase. The resulting microstructure was investigated by transmission electron microscopy. Perpendicular anisotropy was obtained by introducing a Cu/Ti dual underlayer during sputtering, resulting in prefer-orientated SmCo₇ (00L) X-ray diffraction peaks. This study observes a maze-like domain pattern in perpendicular anisotropy films and finds single- and multi-domain particles in correlated AFM and MFM images.     

Synthesis and electrical properties of cubic NaxWO3 thin films across the metal-insulator transition

Highly oriented (1 0 0) Na_xWO₃ thin films were fabricated in the composition range 0.1 ≤ x ≤ 0.46 by pulsed laser deposition technique. The films showed transition from metallic to insulating behaviour at a critical composition between x = 0.15 and 0.2. The pseudo-cubic symmetry of Na_xWO₃ thin films across the transition region is desirable for understanding the composition controlled metal-insulator transition in the absence of any structural phase transformation. The electrical transport properties exhibited by these films across the transition regime were investigated. While the resistivity varied as T² at low temperatures in the metallic regime, a variable range hopping conduction was observed for the insulating samples. For metallic compositions, a non-linear dependence of resistivity in temperature was also observed from 300 to 7 K, whose exponent varied with the composition of the film.     

Properties of thin FePt films synthesized by sequential sputtering of components

Thin (001)-oriented FePt films in the form of multilayer [Pt/Fe] _n structures have been synthesized by means of sequential RF magnetron sputtering of the components. The dependence of the microstructure, magnetic properties, and magnetic anisotropy of the [Pt/Fe] _n system on the substrate temperature during deposition, the type of the first deposited layer, the thicknesses of the partial Fe and Pt layers, and the total film thickness has been studied.     

Preparation and magnetic properties of SrFeO3−x (x = 0.25 ∼ 0.5) using RF magnetron sputtering optimized through sputtering plasma analysis

We investigated the preparation and the magnetic properties of SrFeO_3−x using conventional RF magnetron sputtering. Photoluminescence spectrum analyses of the sputtering plasma revealed that the film composition was changed even using the stoichiometry target. After fixing the composition of the targets from an intensity ratio of the Sr and Fe plasma, the polycrystalline SrFeO_3−x films with different oxygen deficiencies were able to prepare using the various sputtering gas ratio. The magnetic properties of the samples were also changed with changing the sputtering gas ratio. This magnetic property change was likely due to the suppression of the oxygen deficiency in the film.     

Growth of CZTS thin films by sulfurization of sputtered single-layered Cu–Zn–Sn metallic precursors from an alloy target

Cu₂ZnSnS₄ (CZTS) thin films were prepared by sulfurizing single-layered metallic Cu–Zn–Sn precursors which were deposited by DC magnetron sputtering using a Cu–Zn–Sn ternary alloy target. The composition, microstructure and properties of the CZTS thin films prepared under different sputtering pressure and DC power were investigated. The results showed that the sputtering rate of Cu atom increases as the sputtering pressure and DC power increased. The microstructure of CZTS thin films can be optimized by sputtering pressure and DC power. The CZTS thin film prepared under 1 Pa and 30 W showed a pure Kesterite phase and a dense micro-structure. The direct optical band gap of this CZTS thin film was calculated as 1.49 eV with a high optical absorption coefficient over 10⁴ cm^?1. The Hall measurement showed the film is a p-type semiconductor with a resistivity of 1.06 Ω cm, a carrier concentration of 7.904 × 10¹⁷ cm^?3 and a mobility of 7.47 cm² Vs^?1.     

Effect of stacking type in precursors on composition, morphology and electrical properties of the CIGS films

The copper-indium-gallium (CIG) metallic precursors with different stacking type (A: CuGa/CuIn/CuGa/glass and B: CuInGa/CuIn/CuInGa/glass) were prepared onto glass substrates by magnetron sputtering method. In order to prepare Cu(In_1?xGa_x)Se₂ (CIGS) thin films, the CIG precursors were then selenized with solid Se powder using a three-step reaction temperature profile. The influence of stacking type in precursors on structure, composition, morphology and electrical properties of the CIGS films is investigated by X-ray diffraction, energy dispersive spectrometer, scanning electron microscope and Hall effect measurement. The results reveal that the stacking type of the precursor has a strong influence on composition, morphology and properties of the CIGS thin films. The atomic ratios of Cu/(In+Ga)/Se of the CIGS films A and B are 1.61:1:2.11 and 1.39:1:2.04, respectively. The better quality CIGS thin films can be obtained through selenization of metallic precursor of CuInGa/CuIn/CuInGa/glass. The CIGS films are p-type semiconductor material. The hole concentration, resistivity and hole mobility of the CIGS thin films is 2.51 × 10¹⁷ cm^?3, 3.11 × 10⁴ Ω cm and 19.8 cm² V^?1 s^?1, respectively.