DC Magnetron Co-sputtering Research Articles

Mechanical and tribological properties of Ti-Al-Ta-N/TiAl and Ti-Al-Ta-N/Ta multilayer coatings deposited by DC magnetron sputtering

The mechanical properties, microstructure, adhesion and wear behavior of a Ti0.41Al0.48Ta0.11N monolithic coating and Ti0.41Al0.48Ta0.11N/Ti0.45Al0.55 and Ti0.41Al0.48Ta0.11N/Ta multilayers were investigated. The coatings were deposited on titanium substrates by reactive DC magnetron co-sputtering. The hardness and reduced elastic modulus of the coatings were determined by nanoindentation. The multilayer coatings were found to exhibit the lower mechanical characteristics than those of the monolithic coating due to the contribution of the softer metal interlayers to their measured values. Adhesion evaluation was performed by scratch testing. The Ti0.41Al0.48Ta0.11N/Ti0.45Al0.55 multilayer was characterized by stronger adhesion to the titanium substrate than the monolithic coating, whereas the Ti0.41Al0.48Ta0.11N/Ta multilayer exhibited poorer adhesion. In contrast, both the multilayers showed improved wear resistance compared with the monolithic coating. The best wear performance was demonstrated by the Ti0.41Al0.48Ta0.11N/Ti0.45Al0.55 multilayer that was attributed to stronger bonding between the layers as well as the lower hardness of the Ti0.45Al0.55 layers, which allowed for the accommodation of a larger amount of deformation via their plastic flow.

Tribological study of TaTiN/TaTi multilayer films with hierarchical arrangement

The tribological performance of the coatings depends on their properties like material, morphology, structure, among others. This work compares the tribological performance of two multilayers films of ceramic/metallic (TaTiN/TaTi) combination with a hierarchical morphology arrangement using DC-magnetron co-sputtering with Ta and Ti metallic targets controlling the sizes of their ceramic-layer thickness on the Ti substrate. These films had the configuration of the nano to microscales (NML) and micro to nanoscale (MNL) layers. The films had the structure combination of c-TaTiN, c-TiN, and α”-TaTi, with higher Nitrogen in the MNL coatings and higher intensity of LA vibrational mode in their Raman spectra. The XPS study showed that the MNL coating presented a higher metallic composition in the top layer than NML. Nevertheless, MNL film had a higher H and lower E* than NML coating due to the stress distribution by the multilayer arrangement. The MNL coatings showed higher elastoplastic deformation and reduced the presence of cracks and fractures of the layers. The Raman spectra of MNL coating presented a higher presence of Ta2O5 vibrational modes than the MNL film due to a tribolayer formed by debris accumulation.

Effect of Yb-doping on structural and electrical properties of BiFeO3 thin films

In this paper, the incorporation of ytterbium into the BiFeO3 thin film was fabricated on the Pt/Ti/SiO2/Si substrates by using both dc and rf magnetron co-sputtering method at room temperature. The impact of ytterbium content on structural properties and electrical characteristics of the BiFeO3 thin films was investigated. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy techniques were applied to examine the crystal structures, elemental compositions, microstructures, and film morphologies of these thin films, respectively. The Yb-doped BiFeO3 thin film fabricated at the 11 W condition exhibited the lowest leakage current and the highest remnant polarization among these conditions. This result is attributed to the formation of a stronger BiFeO3 (202) component leading to the decrease in oxygen vacancies.

Structure and properties of Ta doped TiN films prepared using different sputtering powers for Ta target

Ta doped TiN films were prepared on glass substrates by DC magnetron co-sputtering. The structure and properties of the obtained (Ti,Ta)N film were characterized by X-ray diffraction, Raman spectroscopy, ultraviolet/visible/near-infrared spectrophotometer and four probes method. The results show that with the increase of the sputtering power (PTa) for Ta target, the amount of Ta added to TiN lattice increases, resulting in a slight distortion of TiN lattice and stress transformation in the film. Correspondingly, the optical and electrical properties of the film changed. Raman spectrum was deconvoluted into five Lorentz peaks in the range of 50-1400 cm?1 and a new Raman peak appeared in all samples due to the substitution of Ta for Ti. The analysis of deconvolution results shows that the peak positions of different phonon modes and FWHM change, which may be related to the change of stress in the thin films caused by adding Ta to TiN lattice. The sample prepared with power of 50W has the maximum infrared emissivity of 1.35 and 0.43 at 2.5 and 25 ?m wavelengths, respectively, indicating that (Ti,Ta)N film is promising candidate for replacing TiN in Low-E glass.

Durability-enhanced monolithic inorganic electrochromic devices with tantalum-doped nickel oxide as a counter electrode

Nickel oxide (NiO) is a well-known electrochromic (EC) material with anodic coloration. However, NiO degrades significantly upon cycling with Li + /H + -conducting electrolytes. Doping with various additives is the most effective method to enhance the cycling stability of NiO films. In this study, films of tantalum-doped nickel oxide, denoted as Ni 1- x Ta x oxide, were deposited onto indium tin oxide (ITO)-coated glass substrates by reactive DC magnetron co-sputtering from Ni and Ta metal targets for use as counter electrodes in monolithic inorganic EC devices (ECDs). The influence of the Ta content on the composition, structure, optical properties and EC properties of NiO was investigated. It was found that the microstructure of the Ni 1- x Ta x oxide films was closely related to the EC performance and cycling stability. With moderate optical modulation, the cycling stability and optical transmittance of the Ni 1- x Ta x oxide film with x = 0.274 were increased. All-solid-state inorganic ECDs were fabricated with the configuration ITO/WO 3 /Ta 2 O 5 /Ni 1- x Ta x oxide/ITO/glass. The full ECDs showed different EC behaviors compared to those of the Ni 1- x Ta x oxide single layers, which was attributed to the different counter electrode/ion conductor interfaces of the solid–solid and solid–liquid interfaces, respectively. The ECD fabricated with the Ni 1- x Ta x oxide film with x = 0.065 showed stable transmittance modulation up to 1000 cycles. We propose a degradation mechanism for monolithic all-solid-state inorganic ECDs based on the observed degradation in the EC performance, which can pave the way for highly durable ECDs for various optoelectronic devices. • Ta-doped Ni oxides were prepared by reactive DC magnetron co-sputtering with Ta content between 0.065 and 0.490. • A Ta content of 0.274 led to the most stable cycling stability with moderate optical modulation. • Ni 1- x Ta x oxide with x = 0.065 is an excellent electrochromic material for highly reliable electrochromic devices.

Structure, phase evolution and properties of Ta films deposited using hybrid high-power pulsed and DC magnetron co-sputtering

Crystalline phase and microstructure control are critical for obtaining desired properties of Ta films deposited by magnetron sputtering. Structure, phase evolution and properties of Ta films deposited by using hybrid high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) under different fractions of DCMS power were investigated, where Ta ion to Ta neutral ratios of the deposition flux were changed. The results revealed that the number of Ta ions arriving on the substrate/growing film plays an important role in structure and phase evolution of Ta films. It can effectively avoid the unstable arc discharge under low pressure and show a higher deposition rate by combining HiPIMS and DCMS compared with only HiPIMS. Meanwhile, the high hardness α-Ta films can be directly deposited by hybrid co-sputtering compared to those prepared by DCMS. In the co-sputtering technology, pure α-Ta phase films with extremely fine, dense and uniform crystal grains were obtained, which showed smooth surface roughness (3.22 nm), low resistivity (38.98 μΩ⋅cm) and abnormal high hardness (17.64 GPa).

Influence of Si content on phase stability and mechanical properties of TiAlSiN films grown by AlSi-HiPIMS/Ti-DCMS co-sputtering

Ti 1−x (Al y Si 1−y ) x N coatings covering a wide compositional range, 0.38 < x < 0.76 and 0.68 ≤ y ≤ 1.00, are deposited to investigate the influence of Al + /Si + ion irradiation on microstructural and mechanical properties. The samples are grown in Ar/N 2 atmosphere by the hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) method with substrate bias synchronized to the Al + /Si + -rich portion of the HiPIMS pulses. Two Ti targets are operated in DCMS mode, while one AlSi target is operated in HiPIMS mode. Four different AlSi target compositions are used: Al 1.0 Si 0.0 , Al 0.9 Si 0.1 , Al 0.8 Si 0.2 , and Al 0.6 Si 0.4 . X-ray diffractometry reveals that films without Si (i.e., y = 1.0) have high Al solubility in NaCl-structure, c-TiAlN, up to x ≤ 0.67 no w-AlN is detected. Once Si (y < 1.0) is introduced the Al solubility limit decreases, but remains higher than other PVD techniques, along with grain refinement and the formation of a SiN z rich tissues phase, as shown by transmission electron microscopy. The nanoindentation hardness is high (~30 GPa) for all films that do not contain the w-AlN phase. All the coatings have compressive stresses lower than −3 GPa. Interestingly, a range of films with different compositions displayed both high hardness (~30 GPa) and low residual stress ( σ < 0.5 GPa). Such a unique combination of properties highlights the benefits of using HiPIMS/DCMS configuration with metal-ion-synchronized substrate bias, which utilizes the Al + /Si + supplantation effect and minimizes the Ar + incorporation. • TiAlSiN films are grown by AlSi-HiPIMS/Ti-DCMS with wide compositional range. • Substrate bias is synchronized to the Al + /Si + -rich portion of the HiPIMS pulses. • The Al + /Si + irradiation effects on film properties are studied. • High Al and Si solubilities in c-TiAl(Si)N are achieved without w-AlN formation. • Specific films yield the combination of low residual stress and high hardness.

Effect of copper concentrations on microstructure, residual stress and corrosion behavior of Ni100−x-Cux alloy films processed by magnetron co-sputtering

Nickel based alloys have gained importance due to their very good mechanical properties as well as their electrochemical behavior in different environmental conditions. In this regard, thin films of nanocrystalline Ni-Cu alloys have been processed by RF / DC magnetron co-sputtering in Ar gas environment for different copper concentration (10 %, 21 %, 28 % and 39 %). Grain size determination, phase identification and residual stress measurement have been done using an X-ray diffraction technique. A compressive residual stress has been observed and the value of the compressive stress increases with an increase in the Cu concentration in the Ni100−x-Cux alloy films. The electrochemical behavior of thin films of the Ni100−x-Cux alloy has been investigated with the help of potentiodynamic polarization experiments which revealed susceptibility towards pitting corrosion. The rate of corrosion decreases from 0.92 ×10−2 to 0.26 ×10−2 mm / year with the increase in Cu concentration from 10 % to 39 %. The microstructure of thin films of the Ni100−x-Cux alloy has been investigated using a field emission scanning electron microscope (FESEM). The FESEM micrograph shows the formation of pits, and the size of pits decreases with increasing concentration of doped Cu. Experimental results also reveal that the increase in corrosion resistance can correlate with the developing residual stress in the films.

The Effect of Working Gases Mixing Ratios on the Synthesis and Characteristics of TiO2/SiO2 Nanocomposite via Closed-Field unbalanced DC Magnetron Co-Sputtering Technique

The objective of this research is to study the influence of deposition parameters such as gases mixing ratio O2/Ar on the structural and optical properties of the TiO2/SiO2 nanocomposite films synthesized using closed field unbalanced dc magnetron co-sputtering technique. The nanocomposite thin films were characterized using x-ray diffraction (XRD) to determine the phase structure, and Fourier transform infrared (FTIR) spectroscopy to investigate Si-O-Si, Ti-O and Si–O–Ti. functional groups. The UV-VIS. absorption spectra of the synthesized films reveal that the indirect energy band gap was found to be 2.75 eV. The mixing ratio of Oxygen and Argon (O2/Ar) gases has a pronounced controlling effect on the structural and optical properties of such nanocomposite.

Effect of Zr content on the structure and morphology of CrZrN thin films prepared by reactive DC magnetron co-sputtering method

In this research, nanostructured chromium zirconium nitride (CrZrN) thin film has been deposited on Si(100) substrates by reactive DC magnetron co-sputtering method without in situ substrate heating and post-deposition annealing. The effects of Zr content on thin film structure and morphology were investigated. The Zr content in the films were varied by applied the sputtering current of Zr target (Izr) in the range of 300 to 900 mA, whereas the current of Cr target was kept at 300 mA. The crystal structure, microstructure, morphology, thickness, and chemical composition were characterized by glancing angle X-ray diffraction (GA-XRD), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques, respectively. The results showed that the increase of Izr not only increased the deposition rate, but also increased the Zr content of the as-deposited film ranging from 3.9 to 26.5 at%. The as-deposited thin films were formed as a (Cr,Zr)N solid solution, with fcc structure in (111) and (200) plane, where Cr atoms were replaced by Zr atoms in the CrN lattice. The 2θ diffraction peaks were shifted to the lower value as increase of Zr content which was obtained by increased Izr. The nanocrystalline CrZrN structure with crystal sizes smaller than 10 nm structure were calculated for as-deposited thin films. The lattice parameters increased from 4.187 to 4.381 Å, whereas the crystal size decreased from 8.3 to 6.4 nm. The FE-SEM images of all the CrZrN films exhibited compact columnar with dense morphology as a function of Zr content. Moreover, the thickness of the CrZrN thin films was increased of 302 – 421 nm.

Studies on superparamagnetic behaviour of Ni100-xCux alloy films deposited by DC magnetron sputtering

ABSTRACT In this study, nanocrystalline Ni100-xCux alloy films have been synthesised using DC magnetron co-sputtering under argon gas atmosphere to analyse their superparamagnetic behaviour. The nanocrystalline nature and the grain size of the alloy films have been measured using grazing incidence x-ray diffraction (GIXRD) and a transmission electron microscopy (TEM). The M-H curves obtained using superconducting quantum interference device provides evidence for superparamagnetic behaviour of the nanocrystalline Ni100-xCux alloy films. For the Ni89Cu11 alloy films, the highest value (456 emu/cm3) of saturation magnetisation has been measured. Zero field cooling (ZFC) and field cooling (FC) data obtained from superconducting quantum interference device (SQUID) showed the dependence of blocking temperature, TB on Cu concentration of the investigated NiCu alloy. The blocking temperature is observed to decrease from 44 K to 33 K with increase in Cu concentration from 11 to 28 wt%.

Low resistivity and near-zero temperature drift ZrB2-Ag composite films prepared by DC magnetron co-sputtering

Nanocrystalline ZrB2-Ag composite films, which utilize Ag nanoparticles as embedded ions, were directly fabricated via the direct current magnetron co-sputtering technique. Keithley Hall Measuring Instrument allowed insight into the physical features in the temperature of 77 K to 373 K. Ag-containing composite film led to resistivity for composite films descended exponentially rather than linearly, however also resulting in the temperature coefficient of resistivity (TCR) values varied from negative to positive. Both comparable lower resistivity (114.9 μΩ·cm) and even near-zero TCR77-373 K at 3 ppm·K−1 indicated that low resistivity and near-zero temperature drift ZrB2-Ag composite film can be obtained by tailoring the Ag content. Moreover, this provides a promising approach to develop sophisticated thin-film resistors (TFR) materials below and above ambient temperature with a broader temperature range.

Approaching Theoretical Band Gap of ZnSnN2 Films via Bias Magnetron Cosputtering at Room Temperature

Zinc tin nitride (ZnSnN2) is a promising semiconductor candidate for solar cell applications and optoelectronic devices. However, the practical use of this material has been limited by several issues as, among others, oxygen contamination, a very high concentration of free carriers, and the difficulty to reach the theoretically predicted band gap. Here, we deposit thin films of ZnSnN2 by reactive DC magnetron cosputtering at room temperature with an RF bias power (Pb) in the range of 0–50 W. Using first principles calculations, we explore the structural and optoelectronic properties that are favorably compared to experimental results. We demonstrate that the optical band gap energy can be decreased from 1.7 to 1.34 eV, close to the predicted value of 1.37 eV. The free electron concentration is decreased down to 1017 cm–3 which results in the reduction of the absorption by free electrons in the IR range. In addition, in a given range of applied bias powers, we observe a densification of the films and a significant decrease of their oxygen contamination from 6.7 down to 2.0 at. %. The study underlines that a value of 20 W power bias leads to the optimal structural, optical, and electrical properties. Our results provide an interesting method to obtain a potential candidate for photovoltaic applications, in an environmentally friendly way, for low-cost industrialization.

Metastable structures in magnetron sputtered W–Zr thin-film alloys

Binary W–Zr thin-film alloys with different metastable structures were prepared by dc magnetron co-sputtering of W and Zr targets in argon atmosphere on unheated and unbiased substrates. The effect of the elemental composition on the formation of different structures and phases was studied in a very wide range of 3–99 at.% Zr. The microstructure and properties of the films were related to the individual metastable structures prepared. We found that W-rich films with an α-W(Zr) solid solution structure can be prepared in much wider range of the elemental composition (up to 24 at.% Zr) than indicated in the equilibrium W–Zr phase diagram. These films exhibited an enhanced hardness (up to 16.1 GPa) and a reduced residual stress (down to −0.05 GPa). Amorphous W–Zr films with a very low surface roughness (down to 0.4 nm) and metallic glass features were prepared with the Zr content between 33 and 83 at.%. The hardness of these films gradually decreased with increasing Zr content due to reducing average bond energy. All films were in the compressive state in contrast to the crystalline ones. The structure of crystalline Zr-rich films with higher than 88 at.% Zr was predominantly dual-phased exhibiting a gradual transition from a metastable β-Zr(W) solid solution (86–96 at.% Zr) through a metastable ω-Zr(W) solid solution (94–100 at.% Zr) to the thermodynamically stable α-Zr phase (99–100 at.% Zr) with increasing Zr (decreasing W) content. We also observed the formation of dual-phase glassy-crystalline structures in the transition zones between fully crystalline and glassy films.

Effect of Ar/N2 flow ratio on the microstructure and mechanical properties of Ti-Cr-N coatings deposited by DC magnetron sputtering on AISI D2 tool steels

Ti-Cr-N coatings were deposited on Si (100) and AISI D2 tool steel substrates by reactive DC magnetron co-sputtering technique from titanium and chromium target in mixed Ar/N2 atmosphere. The Ar/N2 ratio effects on the chemical composition, structure, morphology, intrinsic stress and mechanical properties of the Ti-Cr-N coatings were investigated. The growing process of Ti-Cr-N coatings can be divided into three stages: Stage I, in poisoning mode (low flow ratio 1 < Ar/N2 ≤ 1.4), Stage II, in transition mode (intermediate flow ratio 1.4 ≤ Ar/N2 ≤ 3) and Stage III in metallic mode (Ar/N2 > 3). For all samples, XRD analysis shown the formation of mixed nitrides phases. In stage I, Ti2N, TiN0.3, and hexagonal-Cr2N phases were observed. In Stage II, TiN0.3, Cr2N, and cubic-TiN phases were formed, while only TiN and Cr2N are observed in stage III. The coatings deposited with Ar/N₂ ratio of 3 shows the largest hardness of 24 GPa which is attribute to the dense structure and smoother surface morphology. The properties of the films are discussed in terms of evolution growth stages resulting by the variation of Ar/N2 flow ratios.

ZnOTe Compounds Grown by DC-Magnetron Co-Sputtering

ZnOTe compounds were grown by DC magnetron cosputtering from pure Tellurium (Te) and Zinc (Zn) cathodes in O2/Ar atmosphere. The applied power on the Zn target was constant equal to 100 W, while the one applied on the Te target took two values, i.e., 5 W and 10 W. Thus, two sample series were obtained in which the variable parameter was the distance from the Te targets to the substrate. Sample compositions were determined by Rutherford Backscattering Spectroscopy (RBS) experiments. Structural analysis was done using X-Ray diffraction (XRD) spectrometry and the growth of the hexagonal w-ZnO phase was identified in the XRD spectra. RBS results showed high bulk homogeneity of the samples forming ZnOTe alloys, with variable Te molar fraction (MF) ranging from 0.48–0.6% and from 1.9–3.1% for the sample series obtained at 5 W and 10 W, respectively. The results reflect great differences between the two sample series, particularly from the structural and optical point of view. These experiments point to the possibility of Te doping ZnO with the permanence of intrinsic defects, as well as the possibility of the formation of other Te solid phases when its content increases. The results and appreciable variations in the band gap transitions were detected from Photoluminescence (PL) measurements.

Toward energy-efficient physical vapor deposition: Routes for replacing substrate heating during magnetron sputter deposition by employing metal ion irradiation

In view of the increasing demand for achieving sustainable development, the quest for lowering energy consumption during thin film growth by magnetron sputtering becomes of particular importance. In addition, there is a demand for low-temperature growth of dense, hard coatings for protecting temperature-sensitive substrates. Here, we explore a method, in which thermally-driven adatom mobility, necessary to obtain high-quality fully-dense films, is replaced with that supplied by effective low-energy recoil creation resulting from high-mass metal ion irradiation of the growing film surface. This approach allows the growth of dense and hard films with no external heating at substrate temperatures Ts not exceeding 130 °C in a hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) setup involving a high mass (m > 180 amu) HiPIMS target and metal-ion-synchronized bias pulses. We specifically investigate the effect of the metal ion mass on the extent of densification, phase content, nanostructure, and mechanical properties of metastable cubic Ti0.50Al0.50N based thin films, which present outstanding challenges for phase stability control. Ti0.50Al0.50N based thin films are irradiated by group VIB transition metal (TM) target ions generated by Me-HiPIMS discharge, in which Me = Cr (mCr = 52.0 amu), Mo (mMo = 96.0 amu), and W (mW = 183.8 amu). Three series of (Ti1-yAly)1-xMexN films are grown with x = Me/(Me+Al+Ti) varied intentionally by adjusting the DCMS powers, while y = Al/(Al+Ti) also varies as a result of Me+ ion irradiation. Results reveal a strong dependence of film properties on the mass of the HiPIMS-generated metal ions. All layers deposited with Cr+ irradiation exhibit porous nanostructure, high oxygen content, and poor mechanical properties. In contrast, (Ti1-yAly)1-xWxN films are fully-dense even with the lowest W concentration, x = 0.09, show no evidence of hexagonal AlN precipitation, and exhibit state-of the-art mechanical properties typical of Ti0.50Al0.50N grown at 500 °C. The process energy consumption is lowered by 64% with no negative impact on the coating quality. TRIM simulations provide an insight into the densification mechanisms.

Dense Ti0.67Hf0.33B1.7 thin films grown by hybrid HfB2-HiPIMS/TiB2-DCMS co-sputtering without external heating

There is a need for developing synthesis techniques that allow the growth of high-quality functional films at low substrate temperatures to minimize energy consumption and enable coating temperature-sensitive substrates. A typical shortcoming of conventional low-temperature growth strategies is insufficient atomic mobility, which leads to porous microstructures with impurity incorporation due to atmosphere exposure, and, in turn, poor mechanical properties. Here, we report the synthesis of dense Ti0.67Hf0.33B1.7 thin films with a hardness of ~41.0 GPa grown without external heating (substrate temperature below ~100 °C) by hybrid high-power impulse and dc magnetron co-sputtering (HfB2-HiPIMS/TiB2-DCMS) in pure Ar on Al2O3(0001) substrates. A substrate bias potential of −300 V is synchronized to the target-ion-rich portion of each HiPIMS pulse. The limited atomic mobility inherent to such desired low-temperature deposition is compensated for by heavy-mass ion (Hf+) irradiation promoting the growth of dense Ti0.67Hf0.33B1.7.

Multifunctional ZrB2-rich Zr1-xCrxBy thin films with enhanced mechanical, oxidation, and corrosion properties

Abstract Refractory transition-metal (TM) diborides have high melting points, excellent hardness, and good chemical stability. However, these properties are not sufficient for applications involving extreme environments that require high mechanical strength as well as oxidation and corrosion resistance. Here, we study the effect of Cr addition on the properties of ZrB2-rich Zr1-xCrxBy thin films grown by hybrid high-power impulse and dc magnetron co-sputtering (Cr-HiPIMS/ZrB2-DCMS) with a 100-V Cr-metal-ion synchronized bias. Cr metal fraction, x = Cr/(Zr + Cr), is increased from 0.23 to 0.44 by decreasing the power P ZrB 2 applied to the DCMS ZrB2 target from 4000 to 2000 W, while the average power, pulse width, and frequency applied to the HiPIMS Cr target are maintained constant. In addition, y decreases from 2.18 to 1.11 as a function of P ZrB 2 , as a result of supplying Cr to the growing film and preferential B resputtering caused by the pulsed Cr-ion flux. ZrB2.18, Zr0·77Cr0·23B1.52, Zr0·71Cr0·29B1.42, and Zr0·68Cr0·32B1.38 films have hexagonal AlB2 crystal structure with a columnar nanostructure, while Zr0·64Cr0·36B1.30 and Zr0·56Cr0·44B1.11 are amorphous. All films show hardness above 30 GPa. Zr0.56Cr0.44B1.11 alloys exhibit much better toughness, wear, oxidation, and corrosion resistance than ZrB2.18. This combination of properties makes Zr0·56Cr0·44B1.11 ideal candidates for numerous strategic applications.

Super-exchange interaction model in DMOs: Co doped TiO2 thin films

This work presents a study of the structural, morphological, and magnetic properties of TiO2/Co thin films deposited by DC magnetron co-sputtering of Co and TiO2 targets, varying the concentration of the Co and TiO2 at room temperature. The formation of Co oxides binary phases was not observed. From XRD, μXRD, and Raman measurements were identified rutile and anatase phases, which evidence the formation of diluted magnetic oxide semiconductor (DMOs). Additionally, the TiO2 polymorphous and random location of Co ions are induced when the substrate is at room temperature, and in situ annealing process is applied. SEM, AFM, and MFM micrographs evidenced the formation of smaller grains (< 10 nm) in the surface without relationship with magnetic domains; values of the magnetic roughness were obtained between 199 and 442 pm. Magnetic measurements showed a ferromagnetic-like behavior with the appearance of a magnetic hysteresis loop. The hysteresis curves were associated with a combination of dipolar and super-exchange interactions between Co ions and mediated for oxygen ions based on Anderson’s model; this behavior was described from numerical simulations of isolated magnetic moments (Co atoms) diluted into a non-magnetic matrix (TiO2 structure). In this model, a random distribution of Co ions, contributing to dipolar magnetic interactions and super-exchange interaction, is considered, due to the hybridization sp3d2 of the Co–O bond and located randomly of Co ions. The experimental and theoretical results of this study present an explanation of ferromagnetic-like behavior for Co doped TiO2 thin films, as diluted magnetic semiconductor (DMS) for spintronic applications.