DC Closed-field Unbalanced Magnetron Research Articles

Structural, mechanical and tribological properties of pulsed DC magnetron sputtered TiN–WSx/TiN bilayer coating

Hard-lubricious composite coatings of TiN–WSx with pure TiN under layer were deposited by pulsed DC closed field unbalanced magnetron sputtering in Ar and N2 mixed environment from separate Ti and WS2 targets. The effect of WSx content on the structural, mechanical and tribological properties of the coatings was investigated. EDS analysis of the deposited films revealed that (W+S) content varied from 6.2 to 51.6wt.%. The films were sulphur deficient with S/W at.% ratio in the range of 0.8 to 0.26. The agglomerated grain size, observed through FESEM, progressively became finer with increase in WSx content. Maximum nanohardness of 23.5GPa was obtained for the coating containing minimum content i.e. 6.2wt.% of WSx which gradually decreased with the increase in the WSx content. The adhesion of the coatings, evaluated through scratch adhesion test and indentation adhesion test, also improved with the WSx content up to 14.2wt.%, after which a gradual drop was observed. The pin-on-disc tribological test, revealed lower friction coefficient and lesser wear for the composite bilayer coatings as compared to pure TiN, with the least obtained for the coating exhibiting the maximum adhesion and an intermediate nanohardness. Raman spectra suggested the presence of soft lubricious WS2 phase in the wear debris of composite coating which resulted in less severe three-body abrasion as compared to pure TiN leading to lesser wear.

Electrical and Optical Properties of Fluorine Doped Tin Oxide Thin Films Prepared by Magnetron Sputtering

Fluorine doped tin oxide (FTO) coatings have been prepared using the mid-frequency pulsed DC closed field unbalanced magnetron sputtering technique in an Ar/O2 atmosphere using blends of tin oxide and tin fluoride powder formed into targets. FTO coatings were deposited with a thickness of 400 nm on glass substrates. No post-deposition annealing treatments were carried out. The effects of the chemical composition on the structural (phase, grain size), optical (transmission, optical band-gap) and electrical (resistivity, charge carrier, mobility) properties of the thin films were investigated. Depositing FTO by magnetron sputtering is an environmentally friendly technique and the use of loosely packed blended powder targets gives an efficient means of screening candidate compositions, which also provides a low cost operation. The best film characteristics were achieved using a mass ratio of 12% SnF2 to 88% SnO2 in the target. The thin film produced was polycrystalline with a tetragonal crystal structure. The optimized conditions resulted in a thin film with average visible transmittance of 83% and optical band-gap of 3.80 eV, resistivity of 6.71 × 10−3 Ω·cm, a carrier concentration (Nd) of 1.46 × 1020 cm−3 and a mobility of 15 cm2/Vs.

Structural, mechanical and tribological properties of WS2-Ti composite coating with and without hard under layer of TiN

The present work reports on the structural, mechanical and tribological properties of WS2 and WS2-Ti composite coating with and without hard under layer of TiN. Pulsed DC closed field unbalanced magnetron sputtering was employed for deposition of the films. The films were characterised with energy dispersive X-ray microanalysis (EDX), grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scratch adhesion test, nanoindentation test and pin-on-disc tribological test. The GIXRD spectrum for WS2 film showed prominent orientation of (002) basal plane parallel to the substrate which was also supported by its morphology showing a fine granular structure. Addition of around 13at.% Ti to the WS2 matrix induced turbostratic stacking of the 10 L (L=0, 1, 2,…) planes, however, the (002) orientation was retained. The film’s hardness, adhesion to the substrate, as well as the tribological properties improved with Ti addition. Addition of a hard under layer of TiN resulted in a denser top WS2-Ti layer because of enhanced nucleation promoted by structural defects of the hard under layer. The tribological performance of the top WS2-Ti layer also improved on TiN under layer addition because of the enhanced load bearing capacity of the top layer.

Microstructure, Mechanical, and Scratch Resistance Properties of TiAlCrNbN-Graded Composite Coating Deposited on AISI H13 Steel Substrate with Pulsed DC Closed Field Unbalanced Magnetron Sputtering Method

Structure and adhesion properties of TiAlCrNbN coatings were investigated. These coatings were deposited onto AISI H13 steel substrate using pulsed dc closed field unbalanced magnetron sputtering at different deposition parameters including duty cycle, bias voltage, and working pressure. The coatings have been characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The TiAlCrNbN-graded composite coatings have a dense and columnar structure. The X-ray diffraction patterns of coatings exhibited predominantly c-TiAlCrN, h-NbN, and h-TiAlN reflections. Scratch resistance test showed that the highest adhesion strength was attained as 68 N at 2.5 μs duty time, 100 V bias voltages, and 3 × 10−3 Torr deposition parameters. The lowest adhesion strength was obtained as 55 N at 0.5 μs duty time, 50V bias voltage, and 2 × 10−3 Torr deposition parameters.

Heating Effect on the Qualities of Cr-Zr-N Thin Films by Increasing in Zr Sputtering Current

Chromium zirconium nitride (Cr-Zr-N) thin films have been prepared by reactive dc closed field unbalanced magnetron co-sputtering on Si (100) wafers without external heating and voltage biasing. Heating effect on chemical composition, microstructure, and adhesion of the films by increasing in Zr sputtering current was investigated by using field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX). The results suggested that heating in the film and substrate during the deposition with high Zr target current was caused by bombarding the growing film with high energetic particles. From EDX analysis, the decrease of N content could be an effect of nitrogen desorption caused by heating and bombarding of high energetic particles. FE-SEM cross-sectional morphology revealed that grain refinement by Zr addition and high atomic diffusivity on both surface and bulk by heating and bombarding of high energetic particles resulted in denser fibrous grain microstructure. However, the increase of Zr target current leaded to the film with high compressive stress and could affect the film adhesion.

Structure and Surface Morphology of Cr-Zr-N Thin Films Deposited by Reactive DC Magnetron Sputtering

In this study, chromium zirconium nitride (Cr-Zr-N) thin films have been prepared by reactive dc closed field unbalanced magnetron co-sputtering on Si (100) wafers and glass slides for 60min without substrate heating and biasing voltage in gas mixture of Ar and N2 with flow rates kept constant at 3.0sccm and 6.0sccm, respectively. The sputtering currents applied to Zr target were varied from 0.2 A to 0.8 A, whereas the current of Cr target was kept at 0.8 A. To investigate films structure and surface morphology as a function of Zr content, the as-deposited films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDX). The results suggested that increasing in current applied to Zr target enhanced the deposition rate and also increased Zr content in the films ranging from 6.0 to 31.2 at %. The films formed a solid solution (Cr, Zr)N where Zr atoms substitute Cr atoms in the CrN lattice. The lattice parameters increased from 0.4207nm to 0.4357nm, whereas the grain sizes decreased from 11.27nm to 7.412 nm. The film structure developed with the coexistence of (111) and (200) crystallographic orientation into a mixture of nanocrystalline grains as the sputtering currents of Zr target exceeded 0.2 A. The AFM images showed smoothing surface morphology with the roughness decreased from 9.471nm to 2.437nm. Cross-sectional micrographs exhibited the microstructure evolution corresponding to the grain refinement as a result of increasing Zr discharge current.

Performance of nanolayer CrN/Ag coated cutting tools

A nanolayer CrN/Ag coating comprising a lamination of hard transition metal and soft metal was synthesised using an industrial scale four target dc closed field unbalanced magnetron sputtering ion plating system (CFUBMSIPS). For comparison, a monolayer CrN coating was also grown on the same deposition system. Characterisation was conducted using SEM, TEM, XRD and Vickers microhardness and scratch testers. Wear behaviour was studied on an SRV wear tester. Performance of coated cutting tools was evaluated via two kinds of machining tests: one was using the coated microdrills to continuously make through thickness holes on FR4 printed circuit boards and the other using the coated turning cutters to machine S45C steel bars. The structural analysis showed that the nanolayer CrN/Ag coating with bilayer thickness λ 30 nm was composed of alternative stacking layers of pure Ag and CrN phases. The nanolayer CrN/Ag coating, in spite of having lower hardness than the monolayer CrN coating, showed great improvements in the wear resistance and microdrilling and turning performance, which could be attributed to the combination of multilayer structure and lubricating function of Ag.

High temperature oxidation behavior of CrN/AlN superlattice films

The oxidation behavior of CrN/AlN superlattice films with different bilayer periods (Λ), Al/(Cr + Al) ratios, and crystal structures of the AlN layer was investigated. The films were deposited using a pulsed dc closed field unbalanced magnetron sputtering system. The oxidation tests were carried out in the ambient air at elevated temperatures from 700 to 1100 °C for 1 h. The changes in the crystal phase, microstructure and hardness of the films after the oxidation tests were characterized using X-ray diffraction, scanning electron microscopy and nanoindentation, respectively. When both CrN and AlN layers were in the NaCl cubic structure, the film with Λ = 3.8 nm and an Al/(Cr + Al) ratio of 0.6 exhibited a superior oxidation resistance than the film with Λ = 12.4 nm and an Al/(Cr + Al) ratio of 0.19. The film with Λ = 3.8 nm maintained the nanolayered structure with an oxidation temperature up to 1000 °C by the protection of a thin and dense X-ray amorphous oxide layer. In contrast, when the AlN layers were in the Wurzite hexagonal structure, the film with Λ = 22.5 nm and an Al/(Cr + Al) ratio of 0.67 exhibited poor oxidation resistance. The film lost the superlattice structure at 800 °C and was completely oxidized at 1000 °C due to the formation of a porous crystalline oxide layer on the surface.

Microstructure and tribological properties of Ti-contained amorphous carbon film deposited by DC magnetron sputtering

Pure amorphous carbon (a-C) film and that with a small amount of Ti were deposited on high speed steel (W18Cr4V) substrates by means of dc closed field unbalanced magnetron sputtering. The chemical composition and microstructure of the a-C films were performed using x-ray photoelectron spectroscopy, x-ray diffraction, Raman spectra, and transmission electron microscopy. The mechanical and tribological properties were evaluated using a nanoindentor, Rockwell and scratch tests, and a conventional ball-on-disk tribometer, respectively. The pure a-C film showed the high hardness (53 GPa), elastic modulus (289 GPa), but the poor adhesive strength. When adding a small amount of Ti to the a-C film, both the adhesive strength and the tribological properties were improved. The Ti contained a-C film had the low wear rate (1.9×10−17 m3 N−1 m−1) and friction coefficient in humid air.

Synthesis of carbon barrier film using pulsed DC Closed Field Unbalanced Magnetron Sputtering

Synthesis of carbon barrier film using pulsed DC Closed Field Unbalanced Magnetron Sputtering

Microstructure, mechanical and tribological properties of CrN/W 2N multilayer films deposited by DC magnetron sputtering

CrN/W 2N multilayer films with various bilayer periods of 15–85 nm were deposited on high speed steel (W18Cr4V) substrates by means of DC closed field unbalanced magnetron sputtering. The morphology and microstructure of the multilayer films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The mechanical and tribological properties were evaluated using a nanoindentor, Rockwell and scratch tests and a conventional ball-on-disk tribometer, respectively. There were some transverse grains at the layer interface and the interface between the CrN and W 2N layers was not so sharp owing to atom diffusion through the interface. In the bilayer period range, the microhardness, elastic modulus and adhesive strength of the CrN/W 2N multilayer films increased with the decrease of bilayer period. The CrN/W 2N multilayer film with a bilayer period of 15 nm showed the highest hardness (29.2 GPa), elastic modulus (376 GPa) and best adhesion strength, it also had the highest wear resistance and lowest friction coefficient.