Influence of sputtering parameters and nitrogen on the microstructure of chromium nitride thin films deposited on steel substrate by direct-current reactive magnetron sputtering

Chromium nitride thin films were deposited on SA-304 stainless steel substrates by using direct-current reactive magnetron sputtering. The influence of process conditions such as nitrogen content in the fed gas, substrate temperature, and different sputtering gases on microstructural characteristics of the films was investigated. The films showed (200) preferred orientation at low nitrogen content (< 30%) in the fed gas. The formation of Cr₂N and CrN phases was observed when 30% and 40% N₂ were used, with a balance of Ar, respectively. Field emission scanning electron microscopy and atomic force microscopy were used to characterize the morphology and surface topography of the thin films, respectively. Microhardness tests showed a maximum hardness of 16.95 GPa for the 30% nitrogen content.     

Enhanced photocatalytic activity of silver nanoparticles modified TiO2 thin films prepared by RF magnetron sputtering

Ag-TiO₂ nanostructured thin films with silver volume fraction of 0–40% were prepared by RF magnetron sputtering. The microstructure, surface topography, and optical properties of the films were characterized by X-ray diffractometer, transmission electron microscope, and ultraviolet–visible spectrophotometer. Photocatalytic activity of the films was evaluated by light-induced degradation of methyl orange (C₁₄H₁₄N₃NaO₃S) solution using a high pressure mercury lamp as lamp-house. The relation of photocatalytic activity and silver content was studied in detail. It is found that silver content influences microstructure of TiO₂ thin films, and silver in the films is metallic Ag (Ag⁰). Photocatalytic activity of the films increases with increasing silver content up to 5 vol.% Ag and then decreases to values significantly still bigger than that of pure TiO₂ thin films. Silver nanoparticles significantly enhance the photocatalytic activity of TiO₂ films. The better separation between electrons and holes on silver modified TiO₂ thin films surface allowed more efficiency for the oxidation and reduction reactions. The enhanced photocatalytic activity was mainly attributed to the decrease of energy gap of the films and the increase of oxygen anion radicals O₂⁻ and reactive center of surface Ti³⁺ on silver modified TiO₂ thin films surface.     

Effect of pressure and substrate temperature on the deposition of nano-structured silicon-carbon-nitride superhard coatings by magnetron sputtering

A systematic investigation on the deposition of silicon-carbon-nitride (Si-C-N) films under varying deposition conditions such as pressure, substrate temperature and nitrogen content was carried out by radio frequency and direct current magnetron sputtering techniques. Significant role of the different deposition parameters on hardness and structure in the film was observed. It was observed that there was a certain range of nitrogen to argon partial pressure ratio (90:10 to 98:2) for which the particle size was reduced and the films were smooth with fine particle growth, beyond this limit the films had larger particle growth and roughness. The hardness of the deposited film varied between 4400 Hv and 473 Hv depending on deposition condition. Si-C-N film with hardness above 4400 Hv by reactive RF magnetron sputtering from SiC-C composite target in nitrogen-argon was obtained. X-ray diffraction studies revealed the amorphous nature of the deposited films, whereas nano-crystallinity of the particles was noticed during atomic forced microscopy observations. X-ray photoelectron spectroscopy analysis showed the presence of C-N and Si-N bonds in the harder films. It was found that the presence of β-C₃N₄, Si₃N₄ and graphite phases and the particle growth in the deposited films control the hardness of the film.     

Surface and nanoindentation studies on nanocrystalline titanium diboride thin film deposited by magnetron sputtering

A detailed study on the mechanical, structural and surface characteristics of nanocrystalline TiB₂ films deposited on Si-100 substrates by direct current (DC) magnetron sputtering was carried out. X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), nanoindentaion and X-ray diffraction (XRD) studies on these films were performed. Magnetron sputtered titanium diboride coatings had a maximum hardness of 36 GPa and elastic modulus of 360 GPa. From the XRD analyses, the films were found to grow in (00l) direction-oriented perpendicular to the substrate. The AFM analysis of the films showed the variation of grain size between 30 and 50 nm. The high-resolution AFM images revealed arrangements of atoms resembling lattice and the interplanar spacings measured on the image also showed the orientation of grains in the (001) direction. Nanoindentation studies at very shallow depths showed a continuous increase of hardness and modulus with indentation depth up to 40 nm due to tip blunting and presence of oxides on the film surface (confirmed from the XPS study). The elastic recovery was approximately 69% for 100 nm depth whereas it was 52% for 1000 nm depth.     

Mechanical and deformation behaviour of titanium diboride thin films deposited by magnetron sputtering

Nanoindentation studies have been carried out for TiB₂ films deposited on Si, glass and steel by sputtering for studying the influence of the substrates. It was observed that the modulus of the film was influenced by the substrates from 30 nm onwards. Plastic energy analysis has shown that as load increases more energy is absorbed by the substrate. Quantitative indentation depth limits for obtaining film only hardness, using a combination of log-log plot of load vs displacement and load vs (displacement)² functions, have shown the dependence on the threshold load for crack formation. Comparison of the hardness data with composite hardness models has been performed. Fracture toughness of the coatings was also evaluated using two methods which resulted in comparable results.     

Dielectric oxynitride LaTiOxNy thin films deposited by reactive radio-frequency sputtering

LaTiO_xN_y thin films have been deposited by RF sputtering on (001) Nb-doped SrTiO₃ and (001) MgO single-crystalline substrates at high temperature (T_S = 800 °C) under different nitrogen ratios in the plasma (vol.% N₂ = 0, 25, 71). The band gaps ranged from E_g = 3.30 eV for the epitaxial transparent film containing no nitrogen to E_g = 2.65 eV for the textured coloured film containing a moderate amount of nitrogen. Dielectric characterization in the frequency range [100 Hz-1 MHz], using a metal-insulator-metal structure, has shown a stable permittivity and loss tangent of the epitaxial low-nitrided LaTiO_xN_y film with values of ε′ = 135 and tanδ = 1.2 10^− 2 at 100 kHz (RT).     

Influence of substrate temperature on N-doped ZnO films deposited by RF magnetron sputtering

Nitrogen-doped ZnO films were deposited by RF magnetron sputtering in 75% of N₂ / (Ar + N₂) gas atmosphere. The influence of substrate temperature ranging from room temperature (RT) to 300 °C was analyzed by X-ray diffractometry (XRD), spectrophotometry, X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS) and Hall measurements setup. The XRD studies confirmed the hexagonal ZnO structure and showed that the crystallinity of these films increased with increasing substrate temperature (T_s). The optical studies indicate the average visible transmittance in the wavelength ranging 500-800 nm increases with increasing T_s. A minimum transmittance (9.84%) obtained for the films deposited at RT increased with increasing T_s to a maximum of 88.59% at 300 °C (500-800 nm). Furthermore, it was understood that the band gap widens with increasing T_s from 1.99 eV (RT) to 3.30 eV (250 °C). Compositional analyses (XPS and SIMS) confirmed the nitrogen (N) incorporation into the ZnO films and its decreasing concentration with increasing T_s. The negative sign of Hall coefficients confirmed the n-type conducting.     

Influence of substrate bias voltage on the microstructure and residual stress of CrN films deposited by medium frequency magnetron sputtering

In this study, CrN films were deposited on stainless steel and Si (1 1 1) substrates via medium frequency magnetron sputtering under a systematic variation of the substrate bias voltage. The influence of the substrate bias voltage on the structural and the mechanical properties of the films were investigated. It is observed that there are two clear regions: (1) below −300 V, and (2) above −300 V. For the former region, the (1 1 1) texture is dominated as the substrate bias voltage is increased to −200 V. The lattice parameter is smaller than that of CrN reported in the ICSD standard (4.140 Å) and the as-deposited films exhibit tensile stress. Meanwhile, the surface roughness decreases and the N concentration show a slow increase. For the latter region, the (2 0 0)-oriented structure is formed. However, the lattice parameter is larger as compared with the value reported in the ICSD standard, and the surface roughness increases and the N concentration decreases obviously. In this case, the compressive stress is obtained.     

Characterization of Mo-Al-N nanocrystalline films synthesized by reactive magnetron sputtering

Mo-Al-N films were deposited by a dc reactive magnetron sputtering technique. The effects of N₂ partial pressure, substrate temperature, and aluminum content on the phase composition, microstructure, hardness and oxidation resistance of the films were studied. The MoAlN films as prepared are fcc Mo₂N structure where partial Mo sites were substituted by Al, and the grain size of the crystallites increased from 8 to 30 nm when the Al concentration was increased from 6% to 33%. In the Mo_0.94Al_0.06N film, the hardness can reach 29 GPa, which is much higher than that in binary Mo-N systems. The oxidation resistance temperature of Mo-Al-N film with an Al content of 6% was higher than that of Mo-N films, and with further addition of Al content, the oxidation resistance temperature increased slightly.     

RF reactive magnetron sputtering for Fe-doped titania films deposited from ceramic targets

Fe-doped titania films are prepared by RF magnetron sputtering on Si wafers with specifically designed TiO₂ targets containing different amounts of Fe₂O₃ powder as a dopant source. The physical properties of the films are investigated in terms of the preparation conditions, such as Fe₂O₃ content in the target, RF power, substrate temperature and working pressure. The films show the typical crystallographic orientation. The growth rate increases with increasing RF power, but decreases with working pressure. Films with 40 nm and the transmittance over 90% at the visible region are prepared by using Fe-doped titania target.     

Microstructure and hardness of SiC-TiC nanocomposite thin films prepared by radiofrequency magnetron sputtering

Silicon carbide-titanium carbide (SiC-TiC) nanocomposite thin films were prepared by radiofrequency magnetron sputtering using SiC-TiC composite targets fabricated by spark plasma sintering. The SiC thin films were amorphous at substrate temperatures below 573 K and crystallized in the cubic crystal system (3C) at substrate temperatures greater than 773 K. Cubic SiC-TiC nanocomposite thin films, which contain a mixture of 3C-SiC and B1-TiC phases, were obtained at a TiC content of greater than 20 mol%. The amorphous films possessed a dense cross-section and a smooth surface. The morphology of the SiC-TiC nanocomposite thin films changed from granular to columnar with increasing substrate temperature. The SiC-TiC nanocomposite thin films prepared at TiC content of 70-80 mol% and substrate temperature of 573 K showed the highest hardness of 35 GPa.     

Characterization of organic polymer thin films deposited by rf magnetron sputtering

Organic polymer thin films deposited by sputtering using polytetrafluoroethylene (PTFE) and polyimide (PI) targets were investigated with Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM). Films deposited from the PTFE target were poly-hydro-fluoro-carbon. The thin films showed water repellency with an H₂O contact angle of about 110° and were transparent in the visible region. C-F combination states in the films were similar to those of bulk PTFE. Films deposited from the PI target were found to contain C-N bonds and were harder than bulk PI. The color of thin films was dark brown, showing the existence of C-N bonds, such as those in imide and/or amide groups. However, the combination states characterized by FTIR and XPS analyses were considerably different from those of bulk PI. The difference in chemical composition and combination states between the films deposited from PTFE and PI is thought to result from the difference in types of particles sputtered from the targets; in the case of PTFE sputtering, less C-F bonds are broken by collision of Ar ions for sputtering, whereas in the case of PI sputtering, C-H and C-C bonds are broken by collision of Ar ions.     

Corrosion behaviour of CrN/Cr multilayers on stainless steel deposited by unbalanced magnetron sputtering

This paper reports the results of the influence of bilayer period (Λ) and total thickness (f) on the corrosion resistance of magnetron-sputtered CrN/Cr multilayers. Corrosion tests were carried out by potentiodynamic polarization with 0.5 M H₂SO₄ + 0.05 M KSCN solution and electrochemical impedance spectroscopy (EIS) with 3% NaCl solution. Measurements were also taken on the uncoated substrate and hard chromium coatings for comparison. Multilayer microstructure and morphology were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) and chemical composition was studied by energy dispersive X-ray analysis (EDX).The experiments showed that CrN/Cr coatings having lower bilayer period and lower thickness increased their efficiency as a barrier and improved the corrosion resistance of all coatings evaluated.     

Effect of underlying silicon film on the evolution of microstructure and hardness of the high-temperature annealed carbon film on Si substrate

Effects of an amorphous silicon underlayer on the evolution of microstructure and hardness of an amorphous carbon film annealed at 900 °C for 0.5-1.5 h were investigated. The two-layer carbon/silicon film after annealing resulted in higher sp²/sp³ bonding ratio but lower hardness reduction compared to the single carbon film at the same total film thickness. The improved hardness reduction of the high-temperature annealed carbon film is attributed to the formation of polycrystals of the amorphous silicon together with the residual compressive stress of the two-layer C/Si films.     

Topography and microstructure of Cu-Sn coatings deposited by magnetron sputtering

The topographical and microstructural features of Cu-Sn coatings deposited by magnetron sputtering using alloy target of Cu-7.8%Sn and Cu-74%Sn onto ferritic stainless steel substrates with a temperature gradient were investigated by means of optical and scanning electron microscopy.Depending on the substrate temperature the alloy film forms by a vapour → solid process or a vapour → liquid process with solidification after substrate cooling. In between a mixed mechanism of vapour → liquid → solid occurs during condensation in the temperature ranges 990–1170 K and 460–790 K for coatings deposited by sputtering of Cu-7.8%Sn and Cu-74%Sn targets respectively.The copper-rich condensate formed in the temperature range 370–1220 K consists of a single-phase α solid solution of tin in copper. Its lattice parameter decreases with increasing temperature mainly because of the decreasing tin content.The film obtained by sputtering a Cu-74%Sn target has a two-phase η′-Cu₆Sn₅ plus tin structure independently of the deposition temperature.     

Characterization of the silicon oxide thin films deposited on polyethylene terephthalate substrates by radio frequency reactive magnetron sputtering

Transparent silicon oxide films were deposited on polyethylene terephthalate substrates by means of reactive magnetron sputtering with a mixture of argon and oxygen gases. The influences of process parameters, including the oxygen flow ratio, work pressure, radio frequency (RF) power density and deposition time, on the film properties, such as: deposition rate, morphology, surface roughness, water vapor/oxygen transmission rate and flexibility, were investigated. The experimental results show that the SiO_x films deposited at RF power density of 4.9 W/cm², work pressure of 0.27 Pa and oxygen flow ratio of 40% have better performance in preventing the permeation of water vapor and oxygen. Cracks are produced in the SiO_x films after the flexion of more than 100 cycles. The minimum transmission rates of water vapor and oxygen were found to be 2.6 g/m² day atm and 15.4 cc/m² day atm, respectively.     

Effects of oxygen flow ratios and annealing temperatures on Raman and photoluminescence of titanium oxide thin films deposited by reactive magnetron sputtering

Titanium oxide (TiO_x) thin films were deposited on the Si(100) substrates by direct-current reactive magnetron sputtering at 3-15 % oxygen flow ratios (FO₂% = FO₂/(FO₂ + FAr) × 100%), and then annealed by rapid thermal annealing (RTA) at 350-750 °C for 2 min in air. The phase, bonding and luminescence behaviors of the as-deposited and annealed TiO_x thin films were analyzed by X-ray diffraction (XRD), Raman spectroscopy and photoluminescence (PL) spectroscopy, respectively. The as-deposited TiO_x films were amorphous from XRD and showed weak Raman intensity. In contrast, the distinct crystalline peaks of anatase and rutile phases were detected after RTA at 550-750 °C from both XRD and Raman spectra. A mixture of anatase and rutile phases was obtained by RTA at 3 FO₂% and its amount increased with annealing temperature. Only the anatase phase was detected in the 6-15 FO₂% specimens after RTA. The PL spectra of all post-annealed TiO_x films showed a broad peak in visible light region. The PL peak of TiO_x film at 3 FO₂% at 750 °C annealing can be fitted into two Gaussian peaks at ~ 486 nm (2.55 eV) and ~ 588 nm (2.11 eV) which were attributed to deep-level emissions of oxygen vacancies in the rutile and anatase phases, respectively. The peak around 550 nm was observed at 6-15 FO₂% which is attributed to electron-hole pair recombination from oxygen vacancy state in anatase phase to valence band. The variation of intensity of PL peaks is concerned with the formation of the rutile and anatase phases at different FO₂% and annealing temperatures.     

Investigation on Mn doped ZnO thin films grown by RF magnetron sputtering

In this paper, we have investigated the Zn_1 − x Mn_xO (x = 0.05, 0.10 and 0.15) thin films grown by RF magnetron sputtering. The grown films on sapphire [Al₂O₃(0001)] substrates have been characterized using X-ray Diffraction (XRD), Photoluminescence (PL) and Vibrating Sample Magnetometer (VSM) in order to investigate the structural, optical and magnetic properties of the films respectively. It is observed from XRD that all the films are single crystalline with (002) preferential orientation along c-axis. PL spectra reveal that the addition of Mn marginally shifts the Near Band Edge (NBE) position towards the higher energy side. The magnetic measurements of the films using VSM clearly indicate the ferromagnetic nature.     

Oxidation behavior of Ti-B-C-N coatings deposited by reactive magnetron sputtering

Quaternary Ti-B-C-N coatings with different carbon concentrations are deposited on high-speed steel substrates by reactive magnetron sputtering. The oxidation behavior between 300 and 800 °C under ambient conditions is studied by scanning electron microscopy, high-resolution transmission electron microscopy, Vickers micro-hardness, and X-ray diffraction. The Ti-B-C-N coatings with smaller carbon contents have better oxidation resistance and the oxidation process can be divided into two stages: low-speed oxidation below 700 °C and high-speed oxidation above 700 °C. An oxidation mechanism is proposed to explain the relationship between the reaction with oxygen and observed oxidation behavior.     

Characterizations of CrN/a-CNx nanolayered coatings deposited by DC reactive magnetron sputtering of Cr and graphite targets

CrN/a-CN_x nanolayered coatings have been deposited by DC reactive magnetron sputtering of pure Cr and graphite targets. The total thickness is 1 μm and that of a-CN_x layers is kept constant at 3.5 nm. The period (bilayer thickness) is in the range 8–16 nm. CrN and a-CN_x layers are crystalline and amorphous respectively. The decrease of CrN layers’ thickness (decrease of period) in the stack leads to refinement of CrN microstructure associated with (200) preferred orientation. The hardness of nanolayered films is independent of the period’s thickness, while internal compressive stress, which remains between that of each elementary layer, follows an evolution close to that of the law of mixtures. The best tribological behaviours are reached for a periods’ thickness of 8 nm.