Mechanical properties of superhard TiB2 coatings prepared by DC magnetron sputtering

Superhard titanium diboride (TiB₂) coatings (H_v> 40 GPa) were deposited in Ar atmosphere from stoichiometric TiB₂ target using an unbalanced direct current (d. c.) magnetron. Polished Si (0 0 1), stainless steel, high-speed steel (HSS) and tungsten carbide (WC) substrates were used for deposition. The influence of negative substrate bias, U_s, and substrate temperature, T_s, on mechanical properties of TiB₂ coatings was studied. X-ray diffraction (XRD) analysis showed hexagonal TiB₂ structure with (0 0 01) preferred orientation. The texture of TiB₂ coatings was dependent upon the ion bombardment (U_s increased from 0 to −300 V) and the substrate heating (T_s increased from room temperature (RT) to 700 °C). All TiB₂ coatings were measured using microhardness tester Fischerscope H100 equipped with Vickers and Berkovich diamond indenters and exhibited high values of hardness H_v up to 34 GPa, effective Young's modulus E*=E/(1-ν) ranging from 450 to 600 GPa; here E and ν are the Young's modulus and Poisson's ratio, respectively, and elastic recovery W_e≈80%. TiB₂ coating with a maximum hardness H_v≈73 GPa and E*≈580 GPa was sputtered at U_s=−200 V and T_s=RT. Macrostresses of coatings σ were measured by an optical wafer curvature technique and evaluated by Stoney equation. All TiB₂ coatings exhibited compressive macrostresses.     

离子束溅射沉积Ta2O5光学薄膜的实验研究

根据择优溅射的理论,在不同的通氧方式下,详细分析了离子辅助对离子束溅射沉积Ta2O5薄膜光学特性的影响。结果表明,在薄膜生长的过程中,由于氩离子的轰击作用,薄膜中的氧原子被优先溅射出来,造成了薄膜化学剂量比失调、吸收增加。但是,通过优化辅助离子源中氧气的比例,可获得合理化学剂量比、低损耗的Ta2O5薄膜。     

Tribological properties of Ti2N-Wx% coatings deposited by magnetron sputtering

Ti₂N-W_x% coatings with different tungsten contents were deposited using unbalanced magnetron sputtering technology. The microstructures and mechanical properties of Ti₂N-W_x% coatings have been characterized by SEM, X-ray diffraction (XRD), nanoindentation and adhesion techniques. The tribological performance of the coatings was investigated using an oscillating friction and wear tester under dry conditions. Indexable inserts with Ti₂N-W_x% coatings were applied to turning AISI 1045 steel material by a lathe. Micron-drills with Ti₂N-W_x% coatings were adopted in the ultra-high speed (10⁵ rpm) Printed Circuit Board (PCB) through-hole drilling test. Experimental results indicate that the coating microstructure, mechanical properties and wear resistance vary according to the tungsten content. Ti₂N-W_14% coated inserts showed the best wear resistance in 1045 steel turning and PCB through-hole drilling tests. The service life of a Ti₂N-W_14% coated tool is five times greater than that of an uncoated tool in PCB through-hole drilling test.     

As-grown textured zinc oxide films by ion beam treatment and magnetron sputtering

This work presents as-grown textured ZnO:Al films by rf magnetron sputtering initiated by pre-treatment of glass substrate with mixed argon and oxygen ions. A 650 nm thick of this film exhibits surface texture features with lateral size around 500 nm; the resistivity is below 5 × 10⁻⁴ Ω · cm and the transparency in the near-infrared spectral range is high (> 80% at 1000 nm). Microcrystalline silicon thin film solar cells grown on the textured glass exhibit excellent light trapping effect with a short circuit current density of 18.2 mA/cm².     

Switching properties of vanadium doped TiO2 thin films prepared by magnetron sputtering

In the present work thin films of Ti-Me (where Me: V, Nb, Ta) were deposited onto glass substrates by magnetron sputtering of mosaic target in reactive oxygen plasma. The properties of the prepared thin films were studied by X-ray diffraction (XRD), electron dispersive spectroscopy, temperature-dependent electrical and optical transmission spectroscopy measurements. The structural investigations indicate that thin films were XRD-amorphous. Reversible thermoresistance effect, recorded at 52 ± 1 °C was found from electrical measurements. The prepared coatings were well transparent in the visible part of the light spectrum from ca. 350 nm.     

Structural and mechanical properties of ZrN films prepared by ion beam sputtering with varying N2/Ar ratio and substrate temperature

Zirconium nitride (ZrN) films were deposited by ion beam sputtering technique on stainless steel 304 substrates using a mix of (Ar+N₂) gas. In this paper, the effects of N₂/(N₂+Ar) flow ratio (F(N₂)) and substrate temperature on the microstructure and microscopic properties of the deposited films were investigated. The phase and the morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively; moreover, the composition depth profile of ZrN was obtained using secondary ion mass spectroscopy (SIMS). In a wide range of F(N₂) (10-54%), the intensity of (1 1 1) peak increased which was the preferred orientation, while for F(N₂) more than 54% the ZrN peak intensity was decreased and the amorphous structure was formed at 95%. The XRD patterns presented a texture change due to the processing temperature, which was varied within the range 200-550 °C. At 400 °C, the (1 1 1) crystalline plane intensity was higher than the other ones, leading to the presence of a preference for this orientation. Good planarity of the deposited films was confirmed by SEM, it did not reveal any undulations, fractures, or cracking. The Vickers micro-hardness tester with a load of 25 g was used to measure the hardness of the films. The results showed that the structural and mechanical properties were strongly influenced by nitrogen ratio and substrate temperature.     

Electrical properties of AlNxOy thin films prepared by reactive magnetron sputtering

Direct current magnetron sputtering was used to produce AlN_xO_y thin films, using an aluminum target, argon and a mixture of N₂ + O₂ (17:3) as reactive gases. The partial pressure of the reactive gas mixture was increased, maintaining the discharge current constant. Within the two identified regimes of the target (metallic and compound), four different tendencies for the deposition rate were found and a morphological evolution from columnar towards cauliflower-type, ending up as dense and featureless-type films. The structure was found to be Al-type (face centered cubic) and the structural characterization carried out by X-ray diffraction and transmission electron microscopy suggested the formation of an aluminum-based polycrystalline phase dispersed in an amorphous aluminum oxide/nitride (or oxynitride) matrix. This type of structure, composition, morphology and grain size, were found to be strongly correlated with the electrical response of the films, which showed a gradual transition between metallic-like responses towards semiconducting and even insulating-type behaviors. A group of films with high aluminum content revealed a sharp decrease of the temperature coefficient of resistance (TCR) as the concentration ratio of non-metallic/aluminum atomic ratio increased. Another group of samples, where the non-metallic content became more important, revealed a smooth transition between positive and negative values of TCR. In order to test whether the oxynitride films have a unique behavior or simply a transition between the typical responses of aluminum and of those of the correspondent nitride and oxide, the electrical properties of the ternary oxynitride system were compared with AlN_x and AlO_y systems, prepared in similar conditions.     

Microstructure and mechanical properties of TiAlN/SiO2 nanomultilayers synthesized by reactive magnetron sputtering

TiAlN/SiO₂ nanomultilayers with different SiO₂ layer thickness were synthesized by reactive magnetron sputtering. The microstructure and mechanical properties were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and nano-indentation. The results indicated that, under the template effect of B1-NaCl structural TiAlN layers, amorphous SiO₂ was forced to crystallize and grew epitaxially with TiAlN layers when SiO₂ layer thickness was below 0.6 nm, resulting in the enhancement of hardness and elastic modulus. The maximum hardness and elastic modulus could respectively reach 37 GPa and 393 GPa when SiO₂ layer thickness was 0.6 nm. As SiO₂ layer thickness further increased, SiO₂ transformed back into amorphous state and broken the coherent growth of nanomultilayers, leading to the decrease of hardness and elastic modulus.     

Electrical mechanism analysis of Al2O3 doped zinc oxide thin films deposited by rotating cylindrical DC magnetron sputtering

Cost efficient and large area deposition of superior quality Al₂O₃ doped zinc oxide (AZO) films is instrumental in many of its applications, including solar cell fabrication due to its numerous advantages over indium tin oxide (ITO) films. In this study, AZO films were prepared by a highly efficient rotating cylindrical direct current (DC) magnetron sputtering system using an AZO target, which has a target material utilization above 80%, on glass substrates in argon (Ar) ambient. A detailed analysis on the electrical, optical, and structural characteristics of AZO thin films was performed for the solar cell, as well as display applications. The properties of films were found to critically depend on deposition parameters, such as sputtering power, substrate temperature, working pressure, and film thickness. A low resistivity of ~ 5.5 × 10^− 4 Ω cm was obtained for films deposited at 2 kW, keeping the pressure, substrate temperature and thickness constant at 3 mTorr, 230 °C and ~ 1000 nm respectively. This was due to an increase in carrier mobility and large grain size. Mobility is found to be controlled by ionized impurity scattering within the grains, since the mean free path of carriers is much smaller than the grain size of the films. The AZO films showed a high transparency of ~ 90% in the long wavelength region. Our results offer a cost-efficient AZO film deposition method that can fabricate films with significant low resistivity and high transmittance that can be applied in thin-film solar cells, as well as thin film transistor (TFT) and non-volatile memory (NVM).     

Preparation of SiO2 films with embedded Si nanocrystals by reactive r.f. magnetron sputtering

SiO_x films with a nominal x-value (1≤x≤2) were deposited on flat-surface silicon substrates by reactive r.f. magnetron sputtering at substrate temperatures of 20 and 500°C, respectively. X-ray diffraction and high resolution TEM investigations of SiO_x films with x=1.45 and x=1 show that as-deposited films have an amorphous structure. After annealing, a nucleation of Si nanocrystals was found with increasing size at increasing initial Si concentration and annealing temperature. The weak photoluminescence in the visible region of as-deposited SiO_x films increases remarkably by annealing with dependence on x.     

SiO2/TiO2 thin films with variable refractive index prepared by ion beam induced and plasma enhanced chemical vapor deposition

SiO₂/TiO₂ optical thin films with variable compositions have been prepared by ion beam induced and plasma enhanced chemical vapour deposition (IBICVD and PECVD). While the films obtained by IBICVD were very compact, the PECVD ones with a high content of Ti presented a columnar microstructure. The formation of Si–O–Ti bonds and a change in the environment around titanium from four- to six-coordinated has been proved by vibrational and X-ray absorption spectroscopies. The refractive index increased with the titanium content from 1.45 to 2.46 or 2.09 for, respectively, the IBICVD and PECVD films. Meanwhile, the band gap decreased, first sharply and then more smoothly up to the value of pure TiO₂. It is concluded that the optical properties of SiO₂/TiO₂ thin films can be properly tailored by using these two procedures.     

In situ optical spectroscopy during deposition of Ag:Si3N4 nanocomposite films by magnetron sputtering

In situ and real time surface differential reflectance (SDR) spectroscopy is employed to study the growth of metallic Ag and/or dielectric Si₃N₄ films during deposition by magnetron sputtering. The measurements during Si₃N₄ sputtering allow determining both the refractive index and the deposition rate. During Ag sputtering, the SDR presents a maximum in the visible range, typical of a surface plasmon resonance (SPR) indicating the 3D growth of silver nanoclusters. After a certain deposition thickness, the SDR change corresponds to a continuous layer growth and allows determining the Ag deposition rate. During Ag/Si₃N₄ alternate deposition, the SDR spectroscopy enables to follow the SPR modifications (position, amplitude and width) not only during the formation of the Ag nanoclusters but also during their capping by a Si₃N₄ matrix and during intermediate steps (holding time after the silver sputtering, Si₃N₄ target ignition and pre-sputtering before the Si₃N₄ deposition) where significant changes are detected. It suggests possible nanocluster reshaping or physicochemical processes occurring at the nanocluster interface during the different steps.     

Nanocomposite Al2O3–ZrO2 thin films grown by reactive dual radio-frequency magnetron sputtering

Crystalline alumina–zirconia nanocomposites have been synthesized at 450 °C and 750 °C with reactive magnetron sputtering using radio-frequency power supplies. The composition of the films ranged from pure alumina to pure zirconia as measured by ion beam techniques. Microstructural characterization showed the presence of monoclinic zirconia in the pure zirconia films and γ-alumina in the pure alumina films while the nanocomposites contained either an amorphous compound, γ-alumina, cubic zirconia or a mixture of these. The grain size was  5 nm for the nanocomposite compared to larger grains in the pure oxide films. Electron energy loss spectroscopy showed a clear progression from the pure alumina to the pure zirconia.     

Preparation of B-C-N films by magnetron sputtering with different N2/Ar flow ratio

Amorphous B-C-N films were fabricated on silicon (100) substrates using radio frequency reactive magnetron sputtering technique with variable N₂/Ar flow ratios. The structures, chemical bonding and mechanical properties were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. We found that the N concentration is insensitive to the increment of N₂/Ar flow ratio while the B concentration decreases and C concentration increases. All B-C, C-N, and B-N bond contents increase as the N₂/Ar flow ratio varies from 1/10 to 5/10. Further improving the N₂/Ar flow ratio will promote N atoms prior to bonding with C, resulting in decreased B-C and increased C-N bond content, respectively. The changes of bond content lead to a shift of the main peaks of B1s, C1s, and N1s spectra toward higher binding energies. The hardness of B-C-N thin films is almost invariant with the N₂/Ar flow ratio.     

Photoluminescence of Eu-doped TiO2 thin films prepared by low pressure hot target magnetron sputtering

In this work Eu-doped TiO₂ thin films prepared by reactive magnetron co-sputtering of Ti-Eu metallic target have been studied. The results of photoluminescence (PL) and its correlation with microstructure have been described. Structural properties were examined by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). XRD studies have shown that thin films consisted of TiO₂-anatase and AFM images display their high quality and dense nanocrystalline structure. PL spectra, measured at room temperature, show a dominating strong red luminescence corresponding to ⁵D₀-⁷F₂ transition at ∼ 617 nm and ∼ 623 nm. The evolution of photoluminescence and microstructure of the thin films has been examined as they were additionally annealed in an air ambient.     

Electrical and optical properties of nanostructured VOX thin films prepared by direct current magnetron reactive sputtering and post-annealing in oxygen

Nanostructured vanadium oxide (nano-VO_X) thin films were prepared by direct current magnetron reactive sputtering in mixed O₂/Ar discharges and subsequent annealing in oxygen atmosphere. X-ray diffraction and field emission scanning electron microscope were employed to characterize the crystal structures and morphologies, respectively. Fourier transform infrared spectroscopy was applied to analyze the vanadium-oxygen bonds of films. X-ray photoelectron spectroscopy revealed the compositions of the surface and inner portion of nano-VO_X thin films. It was shown that the as-deposited films were amorphous, and in-situ annealing of these films in ambient oxygen for 10 min can lead to the growth of nano-VO_X thin films. Results of electrical studies indicated that the absolute values of temperature coefficient of resistance and activation energy of films increased significantly after oxygen annealing. Optical investigations carried out in the UV-visible range showed that the absorption edges of nano-VO_X films exhibited large red shifts compared with as-deposited film, and that dual optical absorptions were observed in nano-VO_X films.     

Nd-substituted SrBi2Ta2O9 ferroelectric thin films prepared by radio frequency magnetron sputtering

Nd-substituted SrBi₂Ta₂O₉ (SNBT) thin films are sputtered on Pt/Ta/SiO₂/Si substrates. X-ray diffraction and x-ray photoelectron spectroscopy studies indicate that Nd³⁺ is substituted into the bismuth layered perovskite structure, preferentially at the Sr²⁺ site. The annealed thin film is polycrystalline with plate/needle-like grain microstructure. Secondary ion mass spectrometry results show that elements in SNBT thin film homogeneously distribute along film depth and interfacial diffusion takes place during post annealing. The Nd substitution leads to enhanced remnant polarization (2P_r = 18 μC/cm²) and reduced coercivity (2E_c = 64 kV/cm) at 180 kV/cm measured at 25 °C. After 10¹⁰ switching cycles, around 9% remnant polarization is decreased.     

Luminescence properties of ZnS:Mn nanocrystals embedded in SiO2 by ion implantation

Sequential multi-energy implantations of zinc and sulphur ions have been performed in a 250-nm thick SiO₂ layer thermally grown on 1 1 1 silicon. Energies and doses have been chosen to produce 10 at.% constant concentration profiles overlapping over about 100 nm. Manganese is subsequently introduced at various levels by the same way. Thermal treatments (from 700 to 1100 °C) lead to the formation of nanometric precipitates of the luminescent compound ZnS:Mn. A bimodal size distribution is observed, with a quasi-single layer of large particles (40 nm) in the end-of-range region and much smaller precipitates between this layer and the surface. The orange emission is maximal when the Mn concentration is close to 3%. Several hours at 900 °C is the best thermal budget for maximal luminescence intensity at room temperature. A shift of the excitation spectrum related to size variations, shows that the particles of smaller size are mainly responsible for the observed luminescence. In agreement with other authors, the luminescence lifetime is found in the ms range and increases with the nanocrystal diameter, tending to the lifetime of bulk ZnS. The luminescence of ZnS:Mn nanoparticles embedded in SiO₂ by ion implantation is also shown to be very stable during long UV light irradiation.     

Fabricating highly active mixed phase TiO2 photocatalysts by reactive DC magnetron sputter deposition

Recent work points out the importance of the solid-solid interface in explaining the high photoactivity of mixed phase TiO₂ catalysts. The goal of this research is to probe the structural and functional relationships of the solid-solid interface created by the reactive DC magnetron sputtering of titanium dioxide. We show that sputter deposition provides excellent control of the phase and interface formation. We explored the effects of the process parameters of pressure, oxygen partial pressure, target power, substrate bias (RF), deposition incidence angle, and post annealing treatment on the structural and functional characteristics of the catalysts. We have successfully made pure and mixed phase TiO₂ films. These films were characterized with AFM, SEM, TEM, and XRD to determine surface morphology, phase distribution and phase content. The performance as photocatalytic surfaces was measured and compared (normalized for surface area) to mixed phase TiO₂ fabricated by other methods, including flame hydrolysis powders, and sol-gel deposited TiO₂ films. The sputtered mixed phase materials were far superior to the commercial standard (Degussa P25) and sol-gel TiO₂ as measured by the gas phase oxidation of the air pollutant acetaldehyde under UV illumination. These results demonstrate that reactive DC magnetron sputtering is a powerful tool for investigating the role of the solid-solid interface in influencing photocatalytic activity. In addition, our work illustrates the feasibility of reactive DC magnetron sputtering as a practical commercial technique for manufacturing highly active nanostructured TiO₂ photocatalysts.     

Characterization of CNx films prepared by twinned ECR plasma source enhanced DC magnetron sputtering

The DC discharge of a planar magnetron was enhanced by twinned microwave electron cyclotron resonance plasma source. The magnetic cusp geometry formed in the processing chamber was used for plasma confinement. The sputtering discharge characteristics was investigated and a combined mode of voltage and current was observed at a pressure as low as 0.007 Pa. Carbon nitride thin films were synthesized using this method. Characterization of the films showed that the deposition rate was high, and the films were composed of a single amorphous carbon nitride phase with N/C ratio close to that of C₃N₄, with the bonding mainly of C---N type.