Structure, optical and electrical properties of ZnO thin films on the flexible substrate by cathodic vacuum arc technology with different arc currents

ZnO thin ?lms were successfully deposited onto PET substrates prepared by using cathodic arc plasma deposition (CAPD) technique at a low temperature (<75 °C). Their structure, optical and electrical properties were investigated with various arc currents (40, 45, 50 and 55 A). ZnO (0 0 2) peak was clearly observed, and increased as the arc current increased from 40 A to 55 A. The calculated average crystallized sizes were around 15.9-17.7 nm. The films have an average transmittance over 85% in the visible region, and calculated values of the band gap around 3.33-3.31 eV with increase of the arc current. It was also found that a slight blue shift of optical transmission spectra was observable when decreasing the arc current. The deposited ZnO films had the lowest resistivity; about 3 × 10⁻³ Ω cm for the ZnO ?lm with the arc current of 40 A.     

Properties and tool performance of ta-C films deposited by double-bend filtered cathodic vacuum arc for micro drilling applications

This paper describes the results of the application of ta-C films to micro drilling operation for deep and small machining boreholes. Tetrahedral amorphous carbon (ta-C) films were successfully deposited on WC-Co substrates by a double-bend filtered cathodic vacuum arc (FCVA) system. The structure, mechanical and tribological properties of both pure ta-C and ta-C incorporated argon gas (ta-C:Ar-flow) films were systematically investigated. And then, high-speed through-hole drilling tests were performed on the PCB (printed circuit board) workpiece to investigate the machining performance of ta-C coated micro drills. The experimental results show that the ta-C:Ar-flow (2 sccm) coated micro drill has excellent microstructure, microhardness, and friction coefficient properties and represents the optimal coatings for micro drilling applications.     

Fabrication of DLC thin films with improved diamond-like carbon character by the application of external magnetic field

Diamond-like carbon (DLC) thin films were grown on Si-(100) substrates by a magnetically-assisted pulsed laser deposition (PLD) technique. The role of magnetic field on the structural, morphological, mechanical properties and deposition rate of DLC thin films has been studied. The obtained films were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM) and nanoindentation techniques. It was found that the diamond-like character, thickness and deposition rate of the DLC films increase in the presence of magnetic field. The films deposited under magnetic field exhibit a denser microstructure and smoother surface with lower surface roughness. Meanwhile, the mechanical properties of the magnetically processed DLC thin films experience an improvement, relative to the conventionally processed ones. It seems that the DLC films deposited under magnetic field can be better candidate for hard and wear resistance coating applications.     

Deposition of carbon nitride films by filtered cathodic vacuum arc combined with radio frequency ion beam source

Atomically smooth carbon nitride films were deposited by an off-plane double bend filtered cathodic vacuum arc (FCVA) technique. A radio frequency nitrogen ion source was used to supply active nitrogen species during the deposition of carbon nitride films. The films were characterized by atomic force microscopy (AFM), XPS and Raman spectroscopy. The internal stress was measured by the substrate bending method. The influence of nitrogen ion energy (0–1000 eV) on the composition, structure and properties of the carbon nitride films was studied. The nitrogen ion source greatly improves the incorporation of nitrogen in the films. The ratio of N/C atoms in the films increases to 0.40 with an increase in the ion beam energy to 100 eV. Further increase in the ion beam energy leads to a slight decrease in the N/C ratio. XPS results show that nitrogen atoms in the films are chemically bonded to carbon atoms as C---N, C=N, and CN bonds, but most of nitrogen atoms are bonded to sp² carbon. The increase in nitrogen ion energy leads to a decrease in the content of nitrogen atoms bonded to sp² carbon, and an increase in the content of nitrogen atoms bonded to sp³ and sp¹ carbon. Raman spectra indicate an increase in the sp² carbon phase in carbon nitride films with an increase in nitrogen ion energy. The increase in sp² carbon fraction is attributed to the decrease in internal stress with increasing nitrogen ion energy.     

Effect of different post-annealing durations on electromagnetic properties of La0.67Ca0.33MnO3:Ag0.2 thin films prepared by pulsed laser deposition

La_0.67Ca_0.33MnO₃:Ag_0.2 thin films were obtained by pulsed laser deposition followed by post-annealing at 1200 °C for varied durations. Surface morphologies, structures, and electrical and magnetic properties of films prepared with different annealing durations were significantly different. X-ray diffraction results showed that annealed films exhibited stronger diffraction peaks and C-axis preferred growth. Regarding their electrical properties, metal-insulator transition temperature (T_MI) and temperature coefficient of resistance (TCR) increased first and then decreased with the increase in annealing duration. In terms of their magnetic properties, thin films displayed ferromagnetic-paramagnetic transition. With the increase in annealing duration, Curie temperature increased first and then decreased. Specifically, the film annealed for 3 h showed excellent electromagnetic properties, with relatively high TCR of 20.3%·K^-1 and near room temperature T_MI of 285.7 °C. Owing to these excellent properties, as-prepared thin films have application potential in infrared detectors.     

Influences of bias voltage on properties of TiAl-doped DLC coatings synthesized by cathodic arc evaporation

In this work, the combinations of TiAl-doped DLC (Diamond-like Carbon) and TiAlN/TiN double-layered films were designed to deposit on the tool steels using cathodic arc evaporation in a single process. The economic advantage in depositing the combined coating in one production scale PVD coating system is of practical importance. The TiAl-doped DLC as lubricant coatings were synthesized with TiAl-target arc sources to emit ion plasma to activate acetylene reactive gases. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES), micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) techniques were employed to analysis the microstructure properties of TiAl-doped DLC coatings. Vicker's and tribometer tester were used to measure the mechanical properties of TiAl-doped DLC coatings. The results show that the TiAl-doped DLC coatings retained lower friction coefficient at approximately 0.15 during the steady state sliding. The lubricity and wear resistance of TiAl-doped DLC coatings is then demonstrated to potentially be applied to the cutting tools with no lubricants.     

Effects of aqueous ethanol solutions on the structural and magnetic properties of NiZn ferrite thin films prepared by spin-spray deposition

Although substrate wettability greatly impacts deposition processes using the spin-spray technique, there are few substrates suitable for the deposition of spin-sprayed ferrite thin films. To tune substrate wettability without changing the type of substrate, we demonstrate a Ni_0.17Zn_0.52Fe_2.31O₄ ferrite film deposited by the spin-spray technique on a 0.2 mm glass substrate with 0–5% aqueous ethanol solutions. All samples showed (222) preferential orientation and triangular grain morphology. The effects of aqueous ethanol solutions on the microstructure and magnetic properties of ferrite thin films were also investigated. When the ethanol volume percent concentration equaled 3%, the columnar morphology of the microstructure was most evident and the saturation magnetization and the real permeability reached their maximum values. Because of the shape anisotropy of the columnar structure, the coercivity of the parallel magnetic field increased, whereas the coercivity of the perpendicular magnetic field decreased. First-order inversion curve measurements revealed that ethanol-containing ferrite thin films had a more uniform grain size.     

Si含量对电弧沉积TiAlSiN薄膜性能的影响

利用等离子体辅助电弧沉积技术制备了不同成分的TiAlSiN多元薄膜,并研究了Si含量对薄膜组织结构、显微硬度和耐磨性的影响。XRD物相分析表明:薄膜主要由AlN和TiN组成。随着膜层中Si含量的增加,薄膜的结构由明显的柱状晶转变为致密的玻璃态结构,显微硬度逐渐提高,耐磨性能得到明显改善。     

Thermal stability and mechanical properties of HVOF/PVD duplex ceramic coatings produced by HVOF and cathodic vacuum arc

Duplex ceramic coatings, consisting of an inner NiCr-Cr₃C₂-based coating and an outmost AlCrN film, were produced on the steel substrate in succession by velocity oxygen-fuel spraying (HVOF) and cathodic vacuum arc methods, and then isochronally annealed at annealing temperatures below 900 °C for 2 h. The thermal stability and mechanical properties of the annealed samples were systematically studied by means of X-ray diffraction, Optical microscope and transmission electron microscope, in association with mechanical property measurements. The results show that the microstructure, phase evolution and mechanical properties of duplex ceramic coatings are significantly dependent on the annealing temperature. Metastable fcc-AlCrN solid solution in AlCrN film first decomposes to rich-Al and rich-Cr domains by spinodal decomposition at 700 °C, leading to a notable increase in hardness due to its smaller grain size and high elastic strain field, and then to equiaxed hcp-AlN and Cr₂N by the nucleation and growth at 900 °C, leading to a notable decrease in hardness due to the recrystallization and the formation of hcp-AlN. Meanwhile, the both decarburization of Cr₃C₂ to Cr₇C₃ occurs at 800 °C, but becomes more intensive at 900 °C, leading to a notable loss in hardness. In addition, the dissolution of Cr₃C₂ produces high density of porosity, which also reduces the hardness. The hardness tests show the following ordering of load-bearing capacity for the duplex ceramic coatings: 700 °C>As-deposited >800 °C>900 °C. Tribological property measurements demonstrate that the wear resistance of the tested duplex ceramic coatings obeys the following ordering: 700 °C>As-deposited >800 °C>900 °C. The improved wear resistance is due to high surface hardness, load-bearing capacity and thermal stability. In addition, the wear mechanisms are shown.     

Structure and mechanical properties of W incorporated diamond-like carbon films prepared by a hybrid ion beam deposition technique

W incorporated diamond-like carbon films were prepared on silicon(1 0 0) wafers using a hybrid deposition system composed of an end-Hall-type hydrocarbon ion gun and a tungsten DC magnetron sputter source. The W concentration in the films was controlled by changing the fraction of Ar in the Ar and C₆H₆ reaction gas. The chemical composition, atomic bond structure, and mechanical properties were investigated for W concentrations ranging from 0 to 8.6 at.%. When the W concentration was <2.8 at.%, the W atoms were dissolved in the amorphous carbon matrix without forming a WC_1−x phase. Amorphous and crystalline WC_1−x nano-particles appeared when the W concentration was >2.8 and >3.6 at.%, respectively. It was found that the hardness and elastic modulus were not sensitive to the W concentration in this concentration range. On the other hand, the residual compressive stress was strongly dependent on the chemical state of the incorporated W atoms. The change in mechanical properties is discussed in terms of the microstructural changes induced by W incorporation.     

Structure and properties of Hf-O-N films prepared by high-rate reactive HiPIMS with smoothly controlled composition

Hafnium oxynitride ceramics were prepared in the form of thin films by high-power impulse magnetron sputtering of Hf in various Ar+O₂+N₂ gas mixtures. Smooth composition control was achieved by maximizing the degree of dissociation in plasma, suppressing the importance of the difference between reactivities of undissociated O₂ and N₂. The application potential of the films was further enhanced by extremely high deposition rates (e.g. 230 nm/min for stoichiometric HfO₂; achieved by feedback pulsed reactive gas flow control), low deposition temperatures (<140 °C) and not using any substrate bias. We focus on the relationships between elemental composition, phase structure, and optical, electrical, mechanical and hydrophobic properties of the materials. We quantify the evolution of smoothly controlled film properties along the transition from an oxide to a nitride, such as increasing extinction coefficient, decreasing electrical resistivity, increasing hardness or increasing water droplet contact angle.     

Effects of sintering temperature on structural and electromagnetic properties of MgCuZn ferrite prepared by microwave sintering

Nanocrystalline magnesium–copper–zinc (Mg_0.30Cu_0.20Zn_0.50Fe₂O₄) ferrites were prepared by microwave sintering technique. The effects of the sintering temperature on particle size and magnetic properties were investigated. In this article, optimum sintering temperature required for MgCuZn ferrite system for obtaining good electromagnetic properties, suitable for applications in low temperature co-fired ceramics (LTCC) chip components was studied. The grain size, initial permeability, dielectric constant and saturation magnetisations were found to increase, and dielectric loss was found to decrease with the increasing sintering temperature. Mg–Cu–Zn ferrites with a permeability of μ?=?1110 (at 1?MHz) were fully densified at the standard LTCC sintering temperature of 950°C.     

Microstructural and optical properties of Ta-doped ZnO films prepared by radio frequency magnetron sputtering

Ta-doped ZnO films with different doping levels (0–5.02 at%) were prepared by radio frequency magnetron sputtering. The effects of the doping amount on the microstructure and the optical properties of the films were investigated. The grain size and surface roughness first significantly decrease and then slowly increase with the increase of Ta doping concentration. Both the grain size and the root mean square (RMS) roughness reach their minimum values at the doping content of 3.32 at%. X-ray Diffraction (XRD) patterns confirmed that the prepared Ta-doped ZnO films are polycrystalline with hexagonal wurtzite structure and a preferred orientation along the (002) plane. X-ray photoelectron spectroscopy (XPS) analysis reveals that Ta exists in the ZnO film in the Ta⁵⁺ and Ta⁴⁺ states. The average optical transmission values of the Ta-doped ZnO films are higher than those of the un-doped ZnO film in the visible region. The band gap energy extracted from the absorption edge of transmission spectra becomes large and the near band edge (NBE) emission energy obtained from PL spectra blueshifts to high energy when the Ta doping content grows from 0 at% to 5.02 at%, which can be explained by the Burstein–Moss shift.     

Microstructure and optical properties of nanocrystalline Cu2O thin films prepared by electrodeposition

Cuprous oxide (Cu₂O) thin films were prepared by using electrodeposition technique at different applied potentials (−0.1, −0.3, −0.5, −0.7, and −0.9 V) and were annealed in vacuum at a temperature of 100°C for 1 h. Microstructure and optical properties of these films have been investigated by X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), UV-visible (vis) spectrophotometer, and fluorescence spectrophotometer. The morphology of these films varies obviously at different applied potentials. Analyses from these characterizations have confirmed that these films are composed of regular, well-faceted, polyhedral crystallites. UV–vis absorption spectra measurements have shown apparent shift in optical band gap from 1.69 to 2.03 eV as the applied potential becomes more cathodic. The emission of FL spectra at 603 nm may be assigned as the near band-edge emission.     

Microstructure,mechanical and electrochemical properties of Ti3AlC2 coatings prepared by filtered cathode vacuum arc technology

Ti₃AlC₂ MAX phases have attracted increasing attention due to their unique properties. However, high synthesis temperatures of Ti₃AlC₂ bulk materials limit their further development. In this work, Ti₃AlC₂ coatings were prepared by a two-step method with filtered cathode vacuum arc (FCVA) deposition at room temperature and annealing at 800 °C for 1 h. The structure and properties of coatings were investigated. The results showed that the formation of Ti₃AlC₂ phase in the annealed coating depended on the C₂H₂ flow rate during deposition. At low C₂H₂ flow rates (≤ 9 sccm), almost no Ti₃AlC₂ phase was formed. As the C₂H₂ flow rate increased, the annealed coatings mainly exhibited Ti₃AlC₂ phases, the texture of which transformed from (104) to (105) planes. Meantime, the hardness of Ti₃AlC₂ coatings continuously increased to a maximum of 20.7 GPa, and the corrosion resistance first increased and then decreased with the increase of C₂H₂ flow rate.     

Magnetic properties of metal layer deposited by reduction of metal ions contained in polymer with applying magnetic field

Metal layer was deposited by the reduction of NiCl₂ and CoCl₂ in polyacrylonitrile film after applying an external magnetic field in directions parallel and perpendicular to the surface of the film; the magnetic properties of the metal-deposited film were investigated. When the parallel magnetic field was applied, the values of coercivity (H_c), remanent flux density (B_r) and maximum flux density (B_s) increased regardless of the composition of the metal ions, compared with the case without the application of the magnetic field. From the scanning electron micrographs and X-ray diffraction analyses, it was shown that the growth of crystalline orientation in the deposited metals was enhanced by applying a parallel magnetic field.     

Growth and optical properties of large-scale MoS2 films with different thickness

The synthesis of large-scale molybdenum disulfide (MoS₂) with high quality is highly desirable for the promising applications in flexible optoelectronic devices. Here, we report a feasible one-step chemical vapor deposition (CVD) synthesis of continuous MoS₂ films with different layer-number via adjusting the growth temperature in the range of 740–800 °C. Influences of the annealing treatments at diverse temperature ranging from 300 to 500 °C on Raman and PL spectra of the monolayer MoS₂ film grown at 780 °C are reported. PL characterization shows that the PL emission of film annealed at 400 °C exhibits highest intensity with a blue-shift in comparison to that of the pristine film grown at 780 °C. The PL fluctuation of the MoS₂ film annealed at 400 °C is mainly originated from the high crystalline quality and strain-release. This study sheds a light on growth and performance optimization of the large-area two-dimensional transition metal dichalcogenides films.     

Dielectric and ferroelectric properties of multilayer BaTiO3/NiFe2O4 thin films prepared by solution deposition technique

In this work different lead-free multilayered structures, composed of perovskite BaTiO₃ and spinel NiFe₂O₄ thin layers, were obtained by solution deposition method. Structural characterization of the sintered thin films confirmed the well-defined layered structure with overall thickness from 160 to 600 nm, crystalline nature of perovskite BaTiO₃ and spinel NiFe₂O₄ phases without secondary phases (after sintering below 900 °C) and grains on nanometer scale. Dielectric properties of the multiferroic multilayer BaTiO₃/NiFe₂O₄ thin films were analyzed in temperature and frequency range from 30 °C to 200 °C and 100 Hz to 1 MHz, respectively. In comparison to the pure BaTiO₃ films, the introduction of ferrite layer reduces dielectric response and increases low frequency permittivity dispersion of the multilayer thin films. The multilayer samples have shown relatively low dielectric loss with stronger contribution of conductivity at higher temperatures, and characteristic broad peak representing “relaxation” of the interface charge accumulation.     

Monitoring the dielectric properties of Mn-ferrite nanoparticles by controlling crystallite size and applying static magnetic field

Mn-ferrite (MnFe₂O₄) nanoparticles were synthesized by a co-precipitation method. Temperature annealing and ball milling were used to change the crystallite size. X-Ray diffractograms (XRD) con?rmed the single phase spinel structure for all samples and calculations showed that the crystallite size is in the range of 8–33 nm. Transmission electron microscope (TEM) images reveals 17–43 nm particle sizes. The frequency and crystallite size dependence of resistivity ρ_ac, dielectric constant ε' and dielectric loss ε'' of all samples were studied without magnetic field and under a dc magnetic field that ranges from 0.1 T to 0.5 T in both the parallel and perpendicular directions to the applied electric field. For all samples, ρ_ac, ε' and ε'' were found to decrease with increasing the applied electric field frequency. ρ_ac decreases while ε' and ε'' increase with increasing the crystallite size. On the other hand, they have the reverse trend with applied magnetic field. All factors that affect these parameters were discussed to explain their behavior. Interestingly, it was found that the resistivity depends linearly on the applied magnetic field. This enables these samples to be used as magnetic sensors. Finally, the sensor sensitivity was controlled by changing the crystallite size of the samples. This work establishes valid ideas for promising applications in the field of magnetic sensors.