Optimization of plasma parameters for high rate deposition of titanium nitride films as protective coating on bell-metal by reactive sputtering in cylindrical magnetron device

Nano-structured titanium nitride (TiN) thin film coating is deposited by reactive sputtering in cylindrical magnetron device in argon and nitrogen gas mixtures at low temperature. This method of deposition using DC cylindrical magnetron configuration provides high uniform yield of film coating over large substrate area of different shapes desirous for various technological applications. The influence of nitrogen gas on the properties of TiN thin film as suitable surface protective coating on bell-metal has been studied. Structural morphological study of the deposited thin film carried out by employing X-ray diffraction exhibits a strong (2 0 0) lattice texture corresponding to TiN in single phase. The surface morphology of the film coating is studied using scanning electron microscope and atomic force microscope techniques. The optimized condition for the deposition of good quality TiN film coating is found to be at Ar:N₂ gas partial pressure ratio of 1:1. This coating of TiN serves a dual purpose of providing an anti-corrosive and hard protective layer over the bell-metal surface which is used for various commercial applications. The TiN film's radiant golden colour at proper deposition condition makes it a very suitable candidate for decorative applications.     

Synthesis and characterization of superhard Ti-Si-N films obtained in an inductively coupled plasma enhanced chemical vapor deposition (ICP-CVD) with magnetic confinement

Using a novel inductively coupled plasma enhanced chemical vapor deposition (ICP-CVD) with magnetic confinement system, Ti-Si-N films were prepared on single-crystal silicon wafer substrates by sputtering Ti and Si (5 at.%:1 at.%) alloyed target in argon/nitrogen plasma. High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), atomic force microscopy (AFM) and Nano Indenter XP tester were employed to characterize nanostructure and performances of the films. These films were essentially composed of TiN nanocrystallites embedded in an amorphous Si₃N₄ matrix with maximum hardness value of 44 GPa. Experimental results showed that the film hardness was mainly dependent on the TiN crystallite size and preferred orientation, which could be tailored by the adjustment of the N₂/Ar ratio. When the N₂/Ar ratio was 3, the film possessed the minimum TiN size of 10.5 nm and the maximum hardness of 44 GPa.     

Crystallization of amorphous SiC and superhardness effect in TiN/SiC nanomultilayers

TiN/SiC nanomultilayers with various constituent layer thicknesses were prepared by magnetron sputtering using TiN and SiC ceramic targets. X-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, high-resolution transmission electron microscope, atomic force microscope and nanoindenter were employed to study the growth, microstructure and mechanical properties of these films. Experimental results revealed that amorphous SiC, which is more favorable under normal sputtering conditions, was forced to crystallize and grew epitaxially with TiN layers at thicknesses of less than 0.8 nm. The resultant films were found to form strong columnar structures, accompanied with a remarkable hardness increment. Maximal nanoindentation hardness as high as 60.6 GPa was achieved when SiC thickness was ∼0.6 nm. A further increase of SiC thickness caused the formation of amorphous SiC, which blocked the epitaxial growth of the multilayers, resulting in the decline of film's hardness. Additionally, investigations on multilayers different in TiN layer thicknesses showed that they are insensitive in both microstructure and hardness to the fluctuation of TiN layer thickness. The formation of epitaxially grown structure between crystalline SiC and TiN layers was found to be responsible for the obtained superhardness in multilayers.     

Study of TiN and ZrN thin films grown by cathodic arc technique

Thin films of TiN and ZrN were grown on stainless steel 316 substrate using the pulsed cathodic arc technique with different number of discharges (one to five discharges). The coatings were characterized in terms of crystalline structure, microstructure, elementary chemical composition and stoichiometric by X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy for chemical analyses (XPS), respectively. The XRD results show that for TiN as for ZrN, the preferential direction occurs in the plane (2 0 0), and this result stays when increasing the number of discharges. The grain size is increased with the increase of the number of discharges for both nitrides, the roughness for the TiN film is greater than for the ZrN film; these results were determined by AFM. XPS analysis determined that there is a higher nitrogen presence in the ZrN film than in the TiN film.     

Ti/TiN multilayer thin films deposited by pulse biased arc ion plating

In this work, the effect of modulation period (Λ) on Ti/TiN multilayer films deposited on high-speed-steel (HSS) substrates using pulse biased arc ion plating is reported. The crystallography structures and cross-sectional morphology of Ti/TiN multilayer films were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM), respectively. Their mechanical properties were determined via nanoindentation measurements, while the film/substrate adhesion via the scratch test. It was found that the highest hardness value reached 43 GPa for the modulation period of 54 nm, while the film/substrate adhesion also reached the highest value of 83 N. Furthermore, the hardness enhancement mechanism in the multilayer films is discussed.     

Investigation of the characteristics and corrosion resistance of Al2O3/TiN coatings

Al₂O₃ /TiN double and Al₂O₃/Cr/TiN triple coatings were produced on stainless steel substrates using plasma-detonation techniques. Investigation of the microstructure and characteristics of the coatings after the preparation was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). The corrosion resistance of the coatings was studied in several electrolytic solutions (0.5 M H₂SO₄, 1 M HCl, 0.75 M NaCl) using electrochemical techniques (open circuit potential, cyclovoltammetry and potentiodynamic polarization). The obtained results showed, in most of the cases, an improvement of the corrosion resistance, except in NaCl solutions. The effect of the controlled thickness of TiN and Cr layers as well as the additional treatment with a high-current electron beam was also investigated. Nuclear reaction analysis (NRA), Rutherford backscattering spectroscopy (RBS) and scanning electron microscopy (SEM) were applied for the characterization of the samples before and after the corrosion experiments.     

Epitaxially grown ZnO thin films on 6H-SiC(0 0 0 1) substrates prepared by spin coating-pyrolysis

Epitaxially grown ZnO thin film on 6H-SiC(0 0 0 1) substrate was prepared by using a spin coating-pyrolysis with a zinc naphthenate precursor. As-deposited film was pyrolyzed at 500 °C for 10 min in air and finally annealed at 800 °C for 30 min in air. In-plane alignment of the film was investigated by X-ray pole-figure analysis. Field emission-scanning electron microscope, scanning probe microscope, and He-Cd laser (325 nm) was used to analyze the surface morphology, the surface roughness and photoluminescence of the films. In the photoluminescence spectra, near-band-edge emission with a broad deep-level emission was observed. The position of the near-band-edge peak was around 3.27 eV.     

TiAlN coatings deposited by triode magnetron sputtering varying the bias voltage

TiAlN films were deposited on AISI O1 tool steel using a triode magnetron sputtering system. The bias voltage effect on the composition, thickness, crystallography, microstructure, hardness and adhesion strength was investigated. The coatings thickness and elemental composition analyses were carried out using scanning electron microscopy (SEM) together with energy dispersive X-ray (EDS). The re-sputtering effect due to the high-energy ions bombardment on the film surface influenced the coatings thickness. The films crystallography was investigated using X-ray diffraction characterization. The X-ray diffraction (XRD) data show that TiAlN coatings were crystallized in the cubic NaCl B1 structure, with orientations in the {1 1 1}, {2 0 0} {2 2 0} and {3 1 1} crystallographic planes. The surface morphology (roughness and grain size) of TiAlN coatings was investigated by atomic force microscopy (AFM). By increasing the substrate bias voltage from −40 to −150 V, hardness decreased from 32 GPa to 19 GPa. Scratch tester was used for measuring the critical loads and for measuring the adhesion.     

Characterization of bilayer coatings of TiN/ZrN grown using pulsed arc PAPVD

Nitride coatings have been used to increase hardness and to improve the wear and corrosion resistance of structural materials. Coatings of TiN/ZrN were grown on stainless steel substrates using a physical vapour deposition system assisted by pulsed arc plasma (PAPVD). The coatings have been characterized by X-ray diffraction (XRD) in order to identify the present phases of the films, microstrain level generated, crystallite size and the variation of the lattice parameter. The results showed plane orientations (1 1 1) and (2 0 0) in both TiN and ZrN films. Morphology surface analysis of the samples were performed using a scanning probe microscope to characterize the grain size and roughness in the mode of the atomic force microscopy (AFM) hence it was observed that the root-mean-squared (rms) roughness for ZrN is smaller than for TiN. Besides elastic and friction properties of the films were characterized qualitatively, and then, they were compared with those of the substrates by using force modulation microscopy (FMM) and lateral force microscopy (LFM) modes. In addition, an elemental analysis of the samples was realized by means of energy dispersive spectroscopy (EDS). Both, XRD and AFM results are given as a function of the number of shots. Chemical states of the TiN and ZrN films were determined by X-ray photoelectron spectroscopy (XPS).     

Effect of gun current on the microstructure and crystallinity of plasma sprayed hydroxyapatite coatings

Hydroxyapatite (HA) is a bioactive material because its chemical structure is close to the natural bone. Its bioactive properties make it attractive material in biomedical applications. Gas tunnel type plasma spraying (GTPS) technique was employed in the present study to deposit HA coatings on SUS 304 stainless steel substrate. GTPS is composed of two plasma sources: gun which produces internal low power plasma (1.3-8 kW) and vortex which produces the main plasma with high power level (10-40 kW). Controlling the spraying parameters is the key role for spraying high crystalline HA coatings on the metallic implants. In this study, the arc gun current was changed while the vortex arc current was kept constant at 450 A during the spraying process of HA coatings. The objective of this study is to investigate the influence of gun current on the microstructure, phase crystallinity and hardness properties of HA coatings. The surface morphology and microstructure of as-sprayed coatings were examined by scanning electron microscope. The phase structure of HA coatings was investigated by X-ray diffraction analysis. HA coatings sprayed at high gun current (100 A) are dense, and have high hardness. The crystallinity of HA coatings was decreased with the increasing in the gun current. On the other hand, the hardness was slightly decreased and the coatings suffer from some porosity at gun currents 0, 30 and 50 A.     

Diffusion research between Ni3Al coating and titanium alloy produced by plasma spraying process

A Ni₃Al coating was prepared by plasma spraying technique on the surface of titanium alloy. Ni-Al mixed powders, coatings and reaction products were investigated by scanning electron microscope, EDS, DSC and XRD. A tight bonding between the coating and the substrate was formed. The X-ray diffraction analysis of the patterns showed that the coating not only had Ni₃Al phase, but also had NiO and Al₂O₃ phase microcontent. Comparing Ni coated Al to Ni₃Al at 900 °C, the diffusion was stronger and the diffusion layer was thicker. A minute pore structure was formed at 1200 °C in the front edge of solid-state reaction layer. So Ni₃Al restrained the solid-state reaction of the coating with the substrate, and as a whole weakened the entry of oxygen atoms into the substrate and quenched the out-diffusion of titanium.     

Synthesis of Ti-Si-N nanocomposite coatings by a novel cathodic arc assisted middle-frequency magnetron sputtering

Ti-Si-N nanocomposite coatings were synthesized by using a cathodic arc assisted middle-frequency magnetron sputtering system in an industrial scale. X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy were employed to investigate the chemical bonding and microstructure of the coatings. Atomic force microscope and scanning electron microscope were used to characterize the surface and cross-sectional morphologies of the samples. The coating was found to be nc-TiN/a-Si₃N₄ structure and exhibit a high hardness of 40 GPa when the Si content was 6.3 at.%.     

Fabrication of a superhydrophobic ZnO nanorod array film on cotton fabrics via a wet chemical route and hydrophobic modification

A superhydrophobic ZnO nanorod array film on cotton substrate was fabricated via a wet chemical route and subsequent modification with a layer of n-dodecyltrimethoxysilane (DTMS). The as-obtained cotton sample was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), scanning probe microscope (SPM) and X-ray photoelectron spectroscopy (XPS), respectively. The wettability of the cotton fabric sample was also studied by contact angle measurements. The modified cotton fabrics exhibited superhydrophobicity with a contact angle of 161° for 8 μL water droplet and a roll-off angle of 9° for 40 μL water droplet. It was shown that the proper surface roughness and the lower surface energy both played important roles in creating the superhydrophobic surface, in which the Cassie state dominated.     

Failure behavior of ITO diffusion barrier between electroplating Cu and Si substrate annealed in a low vacuum

A structure of Cu/ITO(10 nm)/Si was first formed and then annealed at various temperatures for 5 min in a rapid thermal annealing furnace under 10⁻² Torr pressure. In Cu/ITO(10 nm)/Si structure, the ITO(10 nm) film was coated on Si substrate by sputtering process and the Cu film was deposited on ITO film by electroplating technique. The various Cu/ITO(10 nm)/Si samples were characterized by a four-point probe, a scanning electron microscope, an X-ray diffractometer, and a transmission electron microscope. The results showed that when the annealing temperature increases near 600 °C the interface between Cu and ITO becomes unstable, and the Cu₃Si particles begin to form; and when the annealing temperature increases to 650 °C, a good many of Cu₃Si particles about 1 μm in size form and the sheet resistance of Cu/ITO(10 nm)/Si structure largely increases.     

Effects of pulsed bias duty ratio on microstructure and mechanical properties of TiN/TiAlN multilayer coatings

TiN/TiAlN multilayer coatings were deposited on M2 high speed steel by a pulsed bias arc ion plating system. The effect of pulsed bias duty ratio on the microstructure, mechanical and wear properties was investigated. The amount of macroparticles reduced with the increase of the duty ratio. The surface roughness was 0.0858 μm at duty ratio of 50%. TiN/TiAlN multilayer coatings were crystallized with orientations in the (1 1 1), (2 0 0) (2 2 2) and (3 1 1) crystallographic planes and the microstructure strengthened at (1 1 1) preferred orientation. At duty ratio of 20%, the hardness of TiN/TiAlN multilayer coatings reached a maximum of 3004 HV, which was 3.2 times that of the substrate. The adhesion strength reached a maximum of 77 N at 50% duty ratio. Friction and wear analyses were carried out by pin-on-disc tester at room temperature. Compared with the substrate, all the specimens coated with TiN/TiAlN multilayer coatings exhibited better tribological properties.     

Ti-Cu-N hard nanocomposite films prepared by pulse biased arc ion plating

In this work, Ti-Cu-N hard nanocomposite films were deposited on high-speed-steel (HSS) substrates using a TiCu (88:12 at.%) single multi-component target by pulse biased arc ion plating. The influence of pulse bias voltages was examined with regard to elemental composition, structure, morphology and mechanical properties of the films. The Cu atomic content of Ti-Cu-N films was determined by Electron Probe Micro-Analyzer (EPMA). The structure and morphology were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Hardness and film/substrate adhesion were determined by nanoindenter and scratch test, respectively. The results showed that the content of Cu appeared to be in the range of 1.75-4.5 at.%, depending on pulse bias voltages. The films exhibit a preferred orientation TiN (1 1 1) texture when the substrate bias voltages were −100 V and −300 V, while the preferred orientation change to be a preferred orientation TiN (2 2 0) one when the substrate bias voltages increase to −600 V and −900 V. And no obvious sign of metal copper phase was observed. The SEM morphologies showed some macroparticles (MPs) on the surface of the films and the relative content of the MPs decreased significantly when the substrate bias voltages increased from −100 to −900 V. The maximum value (74 N) of the film/substrate adhesion of the films was obtained when the substrate bias voltage was −600 V with Cu content of 1.75 at.%. Hardness enhancement was observed, the value of the hardness increased firstly and reached a maximum value of 31.5 GPa, corresponding to Cu content of 1.75 at.%, and then it decreased when the substrate bias voltage changed from −100 to −900 V. The hardness enhancement was discussed related to the concept for the design of hard materials.     

Fabrication and characterization of rod-like nano-hydroxyapatite on MAO coating supported on Mg-Zn-Ca alloy

The poor corrosion resistance of magnesium alloys is a dominant problem that limits their clinical application. In order to solve this challenge, micro-arc oxidation (MAO) was used to fabricate a porous coating on magnesium alloys and then electrochemical deposition (ED) was done to fabricate rod-like nano-hydroxyapatite (RNHA) on MAO coating. The cross-section morphology of the composite coatings and its corresponding energy dispersion spectroscopy (EDS) surficial scanning map of calcium revealed that HA rods were successfully deposited into the pores. The three dimensional morphology and scanning electron microscopy (SEM) image of the composite coatings showed that the distribution of the HA rods was dense and uniform. Atomic force microscope (AFM) observation of the composite coatings showed that the diameters of HA rods varied from 95 nm to 116 nm and the root mean square roughness (RMS) of the composite coatings was about 42 nm, which were favorable for cellular survival. The bonding strength between the HA film and MAO coating increased to 12.3 MPa, almost two times higher than that of the direct electrochemical deposition coating (6.3 MPa). Compared with that of the substrate, the corrosion potential of Mg-Zn-Ca alloy with composite coatings increased by 161 mV and its corrosion current density decreased from 3.36 × 10⁻⁴ A/cm² to 2.40 × 10⁻⁷ A/cm² which was due to the enhancement of bonding strength and the deposition of RNHA in the MAO pores. Immersion tests were carried out at 36.5 ± 0.5 °C in simulated body fluid (SBF). It was found that RNHA can induce the rapid precipitation of calcium orthophosphates in comparison with conventional HA coatings. Thus magnesium alloy coated with the composite coatings is a promising candidate as biodegradable bone implants.     

Bilayer period effect on corrosion-erosion resistance for [TiN/AlTiN]n multilayered growth on AISI 1045 steel

The aim of this work is to study the electrochemical behavior, under a corrosion-erosion condition, of [TiN/AlTiN]_n multilayer coatings with bilayers periods of 1, 6, 12 and 24, deposited by a magnetron sputtering technique on Si (1 0 0) and AISI 1045 steel substrates.The TiN and AlTiN structure for multilayer coatings were evaluated via X-ray diffraction (XRD) analysis. Silica particles were used as an abrasive in the corrosion-erosion test within a 0.5 M H₂SO₄ solution at an impact angle of 30° over the surface. The electrochemical characterization was carried out using a polarization resistance technique (Tafel), in order to observe changes in the corrosion rate as a function of the bilayers number (n) or bilayer period (Λ). Corrosion rate values of 359 mpy in uncoated steel substrate and 1.016×10⁻⁶ mpy for substrate coated with [TiN/AlTiN]₂₄ under impact angle of 30° were found. This behavior was related with the mass loss curve for all coatings and the surface damage was analyzed using SEM images. These results indicate that TiN/AlTiN multilayer coatings deposited on AISI 1045 steel provide a practical solution for applications in erosive-corrosive environments.     

Deformation and fracture of TiN coating on a Si(1 1 1) substrate during nanoindentation

The deformation mechanisms and fracture behavior of TiN coating on a Si(111) substrate, deposited using magnetron sputtering Ti target, is characterized by nanoindentation experiments. The morphologies of the indentations are revealed by scanning electron microscopy, coupled with in situ atomic force microscopy in nanoindentation experiments. The results show that permanent trigonal impressions and radial plastic grooves are confined within the contact regions even though the peak indenter displacement increases to 1500 nm. Local cracks of TiN appear around the indent marks making the edges of the indentations irregular. The cracks increase with an increase of the indenter displacement until the indenter arrives at (or approaches) the Si(1 1 1) substrate at a critical displacement. As the peak indenter displacement increases to 2500 nm, an interfacial fracture between the TiN coating and the Si(1 1 1) substrate is observed using both scanning electron microscopy micrograph and in situ atomic force microscopy images. The diameter of the interfacial fracture determined by scanning electron microscopy micrographs is more accurate than that determined by in situ atomic force microscopy images in nanoindentation experiments. The failure mechanism of the TiN coating is also investigated by means of a standard nanoscratch test.