Solid Solution Films Research Articles

Ta addition effects on the structure, mechanical and thermal properties of sputtered Hf-Ta-C film

Abstract Transition metal carbides (TMCs) hold great promise for protective coatings due to their excellent mechanical properties, however, developing hard yet tough TMC-based materials against harsh environment continues to be a great need but challenge, as high hardness is often obtained with toughness deterioration. Here, we focus on HfC film modification with Ta addition (10.2–26.8 at.%) using magnetron co-sputtering system, particularly, two types phase structures (cubic Hf(Ta)C single-phase solid solution and mixed phase Hf-Ta-C structure (HfC + TaC mixture), respectively) are prepared for comparison and explanation. Mechanical tests reveal that the Hf(Ta)C solid solution film exhibits the highest hardness (36 ± 0.51 GPa), which is far beyond pure HfC and TaC reference, and is nearly two times higher than the film with mixed phase of TaC and HfC. Simultaneously, excellent fracture toughness with high Kf value at 3.6 MPa m1/2 can be achieved in such a solid solution film, on account of high hardness/elasticity modulus ratio. All films exhibit low friction coefficient at∼0.3 when C lubrication medium occurs, the lubrication behavior surpasses corresponding nitrides film. After high-temperature annealing at 800 °C, the Hf(Ta)C solid solution film is found to perform better in terms of thermal stability and oxidation resistance, while structural destruction and obvious oxidation occur in other reference films. We therefore give the potential advantage of solid solution structure (relative to mixed phase structure) in regulating high-performance TMC-based protective coatings, which is fundamental but very practical for other material systems.

Utility of ZnGa2O4 Nanoparticles Obtained Hydrothermally for Preparation of GaN:ZnO Solid Solution Nanoparticles and Transparent Films

GaN:ZnO solid solution nanoparticles and films were synthesized by using ZnGa2O4 nanoparticles with a particle size of below 25 nm obtained hydrothermally as a precursor. Nitridation of powder ZnGa2O4 nanoparticles led to the formation of GaN:ZnO nanoparticles. The nitrided samples have higher specific surface area than those obtained by conventional method, which induces higher photocatalytic NOx decomposition activity. In addition, a transparent coating film with ZnGa2O4 nanoparticles was converted to GaN:ZnO film after nitridation. The nitrided film absorbs UV and blue light and is transparent for light of wavelength over 500 nm (the transmittance is over 90 %). This means that the nitridation does not lead to the formation of scattering domains by the large‐size particles and cracks. This method for film preparation is much cheaper than conventional CVD and sputtering processes. These results strongly suggest the utility of ZnGa2O4 nanoparticles not only for the formation of GaN:ZnO solid solution nanoparticles with high specific surface area but also for the preparation of transparent GaN:ZnO solid solution films.

The influence of Cr content on the phase structure of the Al-rich Al-Cr-O films deposited by magnetron sputtering at low temperature

The Al-rich Al-Cr-O films were directly deposited on Si(100) substrate by reactive radio frequency magnetron sputtering (RFMS) using Al-Cr alloy targets. The elemental composition and phase structure of the films deposited from alloy targets with different Cr content at low substrate temperature were analyzed by electron probe microanalysis (EPMA), grazing incident X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). The results show that the single corundum structured (Al0.7Cr0.3)2O3 solid solution films could be successfully synthesized by sputtering the Al70Cr30 target at low substrate temperature of 550 ℃. The phase structures of the films deposited from Al80Cr20 target exhibit a mixture of Al-rich α-(AlxCr1-x)2O3, Cr-rich α-(AlxCr1-x)2O3, γ-Al2O3 and amorphous phases when the substrate temperature was lower than 550 ℃. The formation of γ phase could be suppressed at 600 ℃ while few amorphous alumina still remains in the film. In order to deposit single phase corundum-type Al-rich (AlxCr1-x)2O3 solid solution films at low temperature, the sufficient Cr content in the films is required.

Квантовые поправки и магнитотранспорт в пленках 3D дираковского полуметалла Cd-=SUB=-3-x-=/SUB=-Mn-=SUB=-x-=/SUB=-As-=SUB=-2-=/SUB=-

In this work we investigated thin films of solid solutions based on the three-dimensional Dirac semimetal Cd3As2 with Mn. The Cd3-xMnxAs2 (x = 0, 0.05 и 0.1) films with thickness around 50 – 70 nm were synthesized on sitall substrates via vacuum thermal evaporation of Mn-doped cadmium arsenide ingots, obtained by the direct melting of components in vacuum ampoules. We measured temperature and magnetic field dependences of films resistivity and defined corresponding transport parameters. Films with x = 0 and 0.05 exhibited positive magnetoresistance with characteristic form, corresponding to the contribution of weak antilocalization effect. At higher Mn content (x = 0.1) we observed the contribution of weak localization effect. Such change of the quantum correction type, in case of topological semimetals, suggest the transformation of the band structure and transition from the Dirac semimetal state into trivial phase, which, in our case, corresponds to the critical Mn content of about xc ~ 0.07.

Solar Photocatalytic Degradation of Trace Organic Pollutants in Water by Bi(0)-Doped Bismuth Oxyhalide Thin Films.

Herein, we demonstrate the fabrication of Bi(0)-doped bismuth oxyhalide solid solution films for the removal of trace organic pollutants (TrOPs) in water. With the advantage of a viscous AlOOH sol, very high loadings (75 wt %) of bismuth oxyhalides were embedded within the thin films and calcined at 500 °C to develop porous alumina composite coatings. Various concentrations of Bi(0) doping were tested for their photocatalytic activity. Seven TrOPs including iopromide (IPRM), iohexol (IHX), iopamidol (IPMD), sulfamethoxazole (SMX), carbamazepine, venlafaxine, and bezafibrate (BZF) were selected for this study based on their occurrence and detection in effluents and surface waters worldwide. In all tests, with the exception of IPRM, 3% Bi(0)-doped BiOCl0.875Br0.125 showed highest activity, which can be attributed to its unique, highly organized, and compact morphology besides its well-matched energy band positions. Although IPMD, IHX, IPRM, and SMX are susceptible to photolysis, still the photocatalytic activity significantly augmented the removal of all tested compounds. In addition, analysis of the surface charge excluded electrostatic interactions and confirmed the ion-exchange adsorption mechanism for the high degradation rate of BZF in the presence of bismuth oxyhalides.

Multilayer formation via spinodal decomposition in TiO2-VO2 epitaxial films on sapphire substrates

We present multilayer formation via spinodal decomposition in rutile TiO2-VO2 (TVO) epitaxial films on sapphire substrates. (001)- and (101)-oriented TVO solid-solution films are grown epitaxially on TiO2/Al2O3 using a pulsed laser deposition technique and annealed inside the spinodal region. X-ray diffraction measurements and scanning transmission electron microscopy (STEM) observations show that the films are phase-separated along the [001] direction and lamellar structures are formed in a parallel or slanted direction to the sapphire substrates depending on the film orientation. The results indicate the multilayer formation via spinodal decomposition in the TVO films. STEM investigations also reveal a relatively high Ti concentration in the decomposed phases, reflecting the influence of lattice deformation on the phase decomposition in the films. Our work shows that spinodal decomposition is a promising approach for the formation of a multilayer structure in TVO films and helps deepen understanding the spinodal decomposition in TVO system.

Solid-solution thin films of ternary BaTiO3–Bi(Mg1/2Ti1/2)O3–BiFeO3 system epitaxially grown on SrRuO3//SrTiO3 substrates via chemical solution process

Lead (Pb)-free perovskite thin films of the ternary BaTiO3–Ba(Mg1/2Ti1/2)O3–BiFeO3 (BT–BMT–BF) solid solution system with preferential crystal orientation were fabricated and the dependence of their polarization behavior on crystal anisotropy was evaluated. The chemical solution deposition (CSD) technique was utilized for the film deposition while controlling the chemical composition. The films fabricated on single-crystal perovskite substrates of (100)SrRuO3//(100)SrTiO3 and (111)SrRuO3//(111)SrTiO3 exhibited preferential (100)pc and (111)pc orientations, respectively, depending on the crystallographic feature on the substrate surface. Excess Bi addition into the precursor solution to compensate for the volatile Bi component enhanced the polarization behavior of the resulting films heat-treated at 750 °C to induce crystallization. The (111)pc-oriented BT–BMT–BF film had a larger remanent polarization (Pr) of approximately 35 µC/cm2 than the (100)pc-oriented film (Pr = approximately 20 µC/cm2).

A horizontal zinc-air battery with physically decoupled oxygen evolution/reduction reaction electrodes

A horizontal Zn-air battery has been designed to enable the use of physically decoupled and catalytically efficient ORR and OER electrodes for discharge and charge, respectively. The horizontal design features a horizontally positioned ORR electrode and a vertically positioned OER electrode, allowing effective management of oxygen transport and pressure. The ORR catalyst (MnOx) and OER catalyst (Co-Fe alloy) are fabricated via one-step electrodeposition on carbon paper and Ni foam, respectively. MnOx is identified as a combination of Mn3O4 nanorods and α-Mn2O3 spheres. Co-Fe is deposited as a solid solution film with an oxidized surface. Electrochemical tests show that both catalysts have comparable or even better activity than their commercial Pt-Ru catalyst counterpart. The catalysts are cycled at 20 mA cm−2 to examine their durability. Cycling potential affects catalyst durability, with improved lifetime under separate ORR and OER conditions compared with the full ORR-OER voltage range. The fabricated catalysts are assembled into a Zn-air battery for discharge-charge cycling tests and show the same average efficiency (58%) as commercial Pt-Ru catalysts.

Giant energy density and high efficiency achieved in bismuth ferrite-based film capacitors via domain engineering

Developing high-performance film dielectrics for capacitive energy storage has been a great challenge for modern electrical devices. Despite good results obtained in lead titanate-based dielectrics, lead-free alternatives are strongly desirable due to environmental concerns. Here we demonstrate that giant energy densities of ~70 J cm−3, together with high efficiency as well as excellent cycling and thermal stability, can be achieved in lead-free bismuth ferrite-strontium titanate solid-solution films through domain engineering. It is revealed that the incorporation of strontium titanate transforms the ferroelectric micro-domains of bismuth ferrite into highly-dynamic polar nano-regions, resulting in a ferroelectric to relaxor-ferroelectric transition with concurrently improved energy density and efficiency. Additionally, the introduction of strontium titanate greatly improves the electrical insulation and breakdown strength of the films by suppressing the formation of oxygen vacancies. This work opens up a feasible and propagable route, i.e., domain engineering, to systematically develop new lead-free dielectrics for energy storage.

Wear Resistance of Cu/Ag Multilayers: A Microscopic Study.

The microscopic wear behavior of copper-silver multilayer samples was studied by performing sliding wear tests using a tribo-indenter. Multilayers with an average composition of Cu90Ag10 and Ag layer thicknesses ranging from 2 to 20 nm were grown by magnetron sputtering. For reference, a homogeneous Cu90Ag10 solid solution film was similarly grown. The thin films were subjected to two-dimensional wear tests by rastering a cono-spherical diamond indenter under loads of 100-400 μN for 1-20 consecutive passes or cycles. The wear volumes were determined by atomic force microscopy. Characterization of the specimens employed nanoindentation, nanoscratch, and transmission electron microscopy (TEM). Wear rates were found to reach steady state after five cycles or less. The hardness values of the as-grown and worn samples both increased with decreasing thickness of the Cu and Ag layers, whereas the steady-state wear rates decreased. Notably, the wear resistance increased faster than the corresponding increase in indentation hardness, indicating a deviation from the Archard's law. An inverse relationship between the wear rate and hardness was, however, recovered when using scratch hardness, suggesting that scratch hardness is a better predictor of wear resistance. Characterization of subsurface wear microstructures by TEM revealed that forced chemical mixing and dissolution of layers occur to a depth of ≈40 to 50 nm, stabilizing a chemically homogeneous solid solution below the wear surface. Comparative wear tests on thicker multilayers revealed that Cu/Ag interfaces reduced the wear rate significantly, thus helping to rationalize the high wear resistance of thin multilayers.

Methods and materials for electroplating aluminum in ionic liquids

The Al-rich Al-Cr-O films were directly deposited on Si(100) substrate by reactive radio frequency magnetron sputtering (RFMS) using Al-Cr alloy targets. The elemental composition and phase structure of the films deposited from alloy targets with different Cr content at low substrate temperature were analyzed by electron probe microanalysis (EPMA), grazing incident X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). The results show that the single corundum structured (Al0.7Cr0.3)2O3 solid solution films could be successfully synthesized by sputtering the Al70Cr30 target at low substrate temperature of 550 ℃. The phase structures of the films deposited from Al80Cr20 target exhibit a mixture of Al-rich α-(AlxCr1-x)2O3, Cr-rich α-(AlxCr1-x)2O3, γ-Al2O3 and amorphous phases when the substrate temperature was lower than 550 ℃. The formation of γ phase could be suppressed at 600 ℃ while few amorphous alumina still remains in the film. In order to deposit single phase corundum-type Al-rich (AlxCr1-x)2O3 solid solution films at low temperature, the sufficient Cr content in the films is required.

Доменный эпитаксиальный рост сегнетоэлектрических пленок титаната бария-стронция на сапфире

AbstractA model of the epitaxial growth of crystalline multicomponent films on single-crystal substrates with a domain correspondence is presented using a solid solution of barium strontium titanate on sapphire substrates ( r cut). The domain epitaxial growth suggests the matching of the lattice planes of the film and the substrate having similar structures by comparison of domain multiple of an integral number of the interplanar spacings. Variation of the component composition of the solid solution enables changes in the domain size in the range sufficient for epitaxial growth. This method can be used to project the epitaxial growth of films of various solid solutions on single-crystal substrates.

Domain epitaxial growth of ferroelectric films of barium strontium titanate on sapphire

A model of the epitaxial growth of crystalline multicomponent films on single-crystal substrates with a domain correspondence is presented using a solid solution of barium strontium titanate on sapphire substrates (r cut). The domain epitaxial growth suggests the matching of the lattice planes of the film and the substrate having similar structures by comparison of domain multiple of an integral number of the interplanar spacings. Variation of the component composition of the solid solution enables changes in the domain size in the range sufficient for epitaxial growth. This method can be used to project the epitaxial growth of films of various solid solutions on single-crystal substrates.

Improved ferroelectric and photovoltaic properties of BiMnO3 modified lead-free K0.5Na0.5NbO3 solid-solution films

Lead-free K0.5Na0.5NbO3/BiMnO3 solid-solution films were deposited on Pt/Ti/SiO2/Si substrates by solution-gelation methods. The effects of the BiMnO3 addition on the electric, bandgap, and photovoltaic properties were investigated systematically. It is shown that, compared with traditional K0.5Na0.5NbO3 films, BiMnO3 modification obviously enhances the ferroelectric properties due to the depression of the leakage current and the improvement of the domain. More importantly, the ferroelectric photovoltaic effect is observed with a large short-circuit current and open-circuit voltage in the lead-free solution films, which is ascribed to the excellent ferroelectric properties and photovoltaic response in the visible region derived from the narrow bandgap modified by BiMnO3. The present work provides strong candidates to be applied in environmentally friendly lead-free ferroelectric photovoltaic solar cell and information storage devices.

Ferroelectric behavior of La and Mn co-doped BiFeO3–PbTiO3 thin films prepared by sol–gel method

Solid solution films of 0.7BiFeO3–0.3PbTiO3, 0.7(Bi0.97La0.03)FeO3–0.3PbTiO3, 0.7Bi(Fe0.96Mn0.04)O3–0.3PbTiO3 and 0.7(Bi0.97La0.03)(Fe0.96Mn0.04)O3–0.3PbTiO3 on Pt/Si structures were fabricated by sol–gel process. Effects of La and Mn doping on microstructures, ferroelectric behavior and leakage current of BiFeO3–PbTiO3 films were investigated. It was found that the coercive field of the BLFPT thin films obviously reduced, owing to the enhancement of domain reversal by the incorporation of La ions. In contrast, Mn-doped films prefer to exhibit the improved polarization and decreased leakage current density. In order to combine the advantages of the two elements’ doping, the films of binary elements co-substitution were successfully prepared. The La and Mn co-doped films demonstrated the best insulation compared with the other samples, which simultaneously achieved the optimized ferroelectric performance with the improved remnant polarization and reduced coercive field. The P r and E c values of co-doped BiFeO3–PbTiO3 thin films at room temperature were approximate 37 uC/cm2 and 90 kV/cm, respectively.

Investigation of the Thermodynamic Properties of Surface Ceria and Ceria–Zirconia Solid Solution Films Prepared by Atomic Layer Deposition on Al2O3

The properties of 20 wt % CeO2 and 21 wt % Ce0.5Zr0.5O2 films, deposited onto a γ-Al2O3 by Atomic Layer Deposition (ALD), were compared to bulk Ce0.5Zr0.5O2 and γ-Al2O3-supported samples on which 20 wt % CeO2 or 21 wt % CeO2–ZrO2 were deposited by impregnation. Following calcination to 1073 K, the ALD-prepared catalysts showed much lower XRD peak intensities, implying that these samples existed as thin films, rather than larger crystallites. Following the addition of 1 wt % Pd to each of the supports, the ALD-prepared samples exhibited much higher rates for CO oxidation due to better interfacial contact between the Pd and ceria-containing phases. The redox properties of the ALD samples and bulk Ce0.5Zr0.5O2 were measured by determining the oxidation state of the ceria as a function of the H2:H2O ratio using flow titration and coulometric titration. The 20 wt % CeO2 ALD film exhibited similar thermodynamics to that measured previously for a sample prepared by impregnation. However, the sample with 21 wt % Ce0.5Zr0.5O2 on γ-Al2O3 reduced at a much higher P O 2 and showed evidence for transition between the Ce0.5Zr0.5O2 and Ce0.5Zr0.5O1.75 phases.

The surface morphology of ZnS–CdS solid solution films

The surface morphology of ZnS–CdS solid solution films

Deformation behavior of Re alloyed Mo thin films on flexible substrates: In situ fragmentation analysis supported by first-principles calculations

A major obstacle in the utilization of Mo thin films in flexible electronics is their brittle fracture behavior. Within this study, alloying with Re is explored as a potential strategy to improve the resistance to fracture. The sputter-deposited Mo1−xRex films (with 0 ≤ x ≤ 0.31) were characterized in terms of structural and mechanical properties, residual stresses as well as electrical resistivity. Their deformation behavior was assessed by straining 50 nm thin films on polyimide substrates in uniaxial tension, while monitoring crack initiation and propagation in situ by optical microscopy and electrical resistance measurements. A significant toughness enhancement occurs with increasing Re content for all body-centered cubic solid solution films (x ≤ 0.23). However, at higher Re concentrations (x > 0.23) the positive effect of Re is inhibited due to the formation of dual-phase films with the additional close packed A15 Mo3Re phase. The mechanisms responsible for the observed toughness behavior are discussed based on experimental observations and electronic structure calculations. Re gives rise to both increased plasticity and bond strengthening in these Mo-Re solid solutions.

Preparation and characterization of ferroelectric Hf0.5Zr0.5O2 thin films grown by reactive sputtering

HfO2-ZrO2 solid-solution films were prepared by radio frequency sputtering, and the subsequent annealing process was optimized to render enhanced ferroelectric behavior. The target power, working pressure and O2 partial pressure ratios were varied, along with the annealing gas, time and temperature. Then, the film’s structural and electrical properties were carefully scrutinized. Oxygen-deficient conditions were necessary during the sputter deposition to suppress grain growth, while annealing by O2 gas was critical to avoid defects and leakage problems. It is expected that the grain size difference under various deposition conditions combined with the degree of TiN top and bottom electrode oxidation by O2 gas will result in different ferroelectric behaviors. As a result, Hf0.5Zr0.5O2 prepared by radio frequency sputtering showed optimized ferroelectricity at 0% of O2 reactive gas, with a doubled remnant polarization value of ∼20 μC cm−2 at a thickness of 11 nm. Film growth conditions with a high growth rate (4–5 nm min−1) were favorable for achieving the ferroelectric phase film, which feasibly suppressed both the grain growth and accompanying monoclinic phase formation.

A technique for the local doping and correction of the conductivity of PbSnTe epitaxial layers via indium diffusion from superficial nanometer-thick films

A technique is described for the local indium doping of epitaxial films of a p-type PbSnTe solid solution to obtain a metal-insulator transition at liquid-helium temperatures. The indium was diffused from the surface of the film, from an In layer several nanometers thick, whereas the shape and size of the doped layer were set by a mask. It is emphasized that the oxide layer should be removed before indium deposition, and that the thickness of the deposited indium layer should be precisely chosen based on the thickness of the PbSnTe film. The results of using this technique for films having different compositions and the results of measurements performed on a planar p-i-p structure are considered.