Direct Current Magnetron Sputtering Technique Research Articles

Influence of Nitrogen on the Microstructure, Hardness, and Tribological Properties of Cr–Ni–B–C–N Films Deposited by DC Magnetron Sputtering

Using the direct current reaction magnetron sputtering technique, Cr–Ni–B–C–N films are deposited onto silicon substrates by sputtering Cr–Ni and B–C targets in an Ar/N2 gas mixture. The microstructure, chemical bonds, hardness, and tribological properties of the films are characterized using the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) methods, and microindentation and tribological tests. The experimental results show that the microstructure and properties of the films change upon incorporation of nitrogen into the film composition. The Cr–Ni–B–C–N films are mainly composed of the nanocrystalline CrN phase with some fractions of the Ni, Cr2O3, and B2O3 crystalline phases embedded in a mixed amorphous environment. Addition of nitrogen gives rise to an increase in the film hardness to a maximum value of about 17 GPa at FN2 = 40 cm3/min, and then the hardness sharply decrease with a further increase in the FN2 flow rate. The incorporation of nitrogen into the structure of films improves their tribological and adhesion properties.

Research on the influence of the filtrating electrode on the structure and optical properties of TiO2 thin films prepared by the energy filtering magnetron sputtering technique

Abstract TiO2 thin films were deposited by the energy filtrating magnetron sputtering (EFMS) technique and the traditional direct current magnetron sputtering (DMS) technique. The influence of the filtering electrode mesh number on the structure and optical properties of TiO2 thin films was investigated. The structure, surface morphology and optical properties were characterized by XRD, SEM and ellipsometric spectroscopy, respectively. Results show that the TiO2 thin films deposited by the DMS and EFMS techniques at the same deposition parameters are composed of the anatase phase exclusively. TiO2 thin films deposited at lower deposition rate by the EFMS technique have lower crystallinity, smaller particle size and smoother surface. With increasing the mesh number, the refractive index, extinction coefficient and optical band gap are larger.

Alternating current impedance spectroscopic investigation of an a-Si:H/c-Si heterojunction with porous silicon multilayers

In this paper, we study structures contained thin hydrogenated amorphous silicon (a-Si:H) films deposited on porous silicon multilayers (Distributed Bragg Reflector DBR) formed by electrochemical etching of crystalline silicon (c-Si) wafers. The a-Si:H thin films were deposited by the Direct-current magnetron sputtering technique in a mixture of argon and hydrogen atmosphere. It is shown in our previous work that the Bragg mirrors formed on crystalline silicon play an important role in the light trapping in a-Si:H. The structural features of porous silicon, in terms of porosity, thickness and surface roughness, were determined using spectroscopic ellipsometry. The elaborated structures were analysed by impedance spectroscopy. The fit of data obtained from the impedance spectroscopy allowed us to determine the electrical equivalent circuit. This permits the identification of the electronic behaviour of the structures and allows us to explain the role of their different components, including the interfaces. For this purpose, we have proceeded successively. First, by the characterisation of porous silicon monolayers, afterward structures formed by porous silicon multilayers as DBR and structures of a-Si:H/c-Si and a-Si:H/PSi(DBR)/c-Si are characterised. A negative capacitance was found for the heterojunction with DBR, which was attributed to the existence of defect states at the interfaces between porous and amorphous silicon.

The superior properties of CrN coatings prepared by high power pulsed reactive magnetron sputtering

In this paper, we investigate the properties of chromium nitride (CrN) coating prepared using a high power magnetron sputtering (HiPIMS) technique. As a comparison, CrN coating prepared using a direct current magnetron sputtering (DCMS) technique is also studied. The crystal structure, surface and cross-sectional morphologies, and composite properties of the as-deposited CrN coatings are compared by x-ray diffraction, a scanning electron microscope, and a microhardness tester, respectively. It is found that the as-deposited CrN film by HiPIMS grew preferentially on (200) facet when compared with that by DCMS on (111) facet. As a result, the coatings deposited by HiPIMS have a very compact microstructure with high hardness: the microhardness reached 855.9 Hv replacing 501.5 Hv by DCMS. Besides, the inner-stress of CrN films prepared by HiPIMS is also relatively small. After measuring the corrosion resistance, the corrosion current of films prepared by HiPIMS was an order of magnitude smaller than that of CrN films deposited by DCMS. Based on the plasma diagnostics by time resolved optical emission spectroscopy, it is believed that the superior quality of CrN coatings prepared by HiPIMS is because of the ionic reaction between Cr+ and N+, rather than the neutral Cr and N reaction in DCMS during the CrN film growth.

Influence of Argon/oxygen Ratio on Linear and Nonlinear Optical Properties of Copper Doped ZnO Films

Copper (Cu)-doped ZnO (CZO) films were grown by simultaneous direct current and radio frequency magnetron sputtering technique under the situation of different gas flow rates of Ar: O2 (1:1, 2:1 and 1:0). The X-ray diffraction patterns revealed the naturally polycrystalline ZnO films with the predominant reflection (002) peak, which referred to the hexagonal wurtzite structure toward c-axis. The elemental composition of thin films was analyzed by energy dispersive spectroscopy (EDS). The Cu concentrations in thin films increased with Ar ratio of up to 1:0. The EDS spectra of three kinds of elements indicate that Cu-doping has obvious and sophisticated effect on the chemical state of oxygen, but less effect on those of copper and zinc. Furthermore, the nonlinear absorption of CZO films was investigated by the way of Z-scan technique. These films demonstrated good nonlinear absorption behavior for the different gas flow rates of Ar: O2.

Modification in ZnO film properties by 250 keV cobalt implantation

Direct current magnetron sputtering technique was used to synthesize ZnO films on PET (Polyethylene terephthalate) substrate. The as-synthesized films were exposed to 250 keV cobalt (Co) ions by Pelletron Accelerator at different ion fluences (in range of 1011 to 1014 ions cm−2). The lattice constant, crystallite structure, size and strain of pristine and Co-implanted films were studied through x-ray diffraction (XRD) method. The study showed that the ZnO film became partially amorphous after Co implantation up to the fluence of 1013 ions cm−2. However, Co implantation at 1014 ions cm−2 slightly restored the film’s crystallinity due to ion-induced localized heating. Tauc equation was used to estimate the band gap of pristine and Co implanted films. The band gap of Co implanted ZnO was decreased by increasing the ion fluence that was ascribed to a decrease in the conduction band tail due to overlapping of donor defect levels. Electrical measurements showed that the ZnO film became more conductive with increasing the Co fluence.

Comparison of thermoelectric properties of flexible bismuth telluride thin films deposited via DC and RF magnetron sputtering

Bi2Te3 thin films were deposited onto polyamide sheets with direct current (DC) or radio frequency (RF) magnetron sputtering techniques. The films were prepared using a Bi2Te3 target at a varying pre-heating temperature from 150 to 350 °C. It was observed that the type of plasma excitation and pre-heating temperature can significantly change the composition, preferred orientation, crystallinity, and thermoelectric properties of the films. The pre-heat treatment significantly affected the non-stoichiometric composition. In addition, it was shown that crystallinity and (0 0 l) planes were enhanced in the DC sputtered coatings at a high pre-heating temperature. The maximum power factor of 3.5 × 10−3 W/m K2 at 285 °C was obtained for the films deposited using DC magnetron sputtering and a pre-heating temperature of 350 °C. The carrier concentration and mobility of the film were 5.40 × 1020 cm−3 and 13.04 cm2/V s, respectively. Compared with an ordinary Bi2Te3 film, the power factor of such film has been greatly increased. The results indicated that DC magnetron sputtering can enhance the (0 0l ) plane orientation in the Bi2Te3 film.

Preparation and characterization of heat-insulating Ag/TiO2 composite membranes based on magnetron sputtering technology

Abstract

Understanding the Preferred Crystal Orientation of Sputtered Silver in Ar/N2 Atmosphere: A Microstructure Investigation

Silver thin films were prepared by direct current (DC) magnetron sputtering technique in Ar/N2 atmosphere with various N2 volumetric ratios on Si substrates. Silver thin films prepared in pure Ar atmosphere show highly (111) preferred orientation. However, as the N2 content increases, Ag (111) preferred orientation evolves into (100) preferred orientation gradually. When N2 content is more than 12.5 vol.%, silver thin films exhibit highly (100) preferred orientation. Moreover, the average grain size decreases with increasing N2 content. Silver thin films with low relative density are prepared at high N2 content, which results in higher resistivity of films. By analyzing the resistivity and microstructures of silver thin films, the optimum range of N2 content to get compact silver thin films is found to be not more than 33.3 vol.%. Finally, the mechanism of N2 addition on microstructure evolution of silver thin films was proposed.

Investigation on the influence of oxygen on the deformation and cracking behavior of (Cr,Al)ON hard coatings using combinatorial static and dynamic loadings

The coating system (Cr,Al)ON can enhance the wear and corrosion resistance of tools applied in technical applications. It is possible that, under different loading conditions, the oxygen content of the coating could influence the performance of the coated tools. The aim of the present work is to study the influence of the oxygen content of the coating system (Cr,Al)ON on its elastic-plastic deformation and cracking behavior under static and dynamic loading conditions. For these purposes, three (Cr,Al)ON coatings with different oxygen contents were deposited on a quenched and tempered tool steel substrate AISI 420. The coatings were deposited using a hybrid technology combining direct current and high power pulse magnetron sputtering techniques in an industrial coating unit. The investigations were carried out by applying static loadings using nanoindentation and Rockwell tests as well as dynamic loading conditions using nanoscratch tests. Qualitative investigations were carried out using confocal laser scanning microscopy. The analyses of Rockwell imprints and nanoscratch tracks were conducted through scanning electron microscopy. Test results show that an improved understanding of possible crack formation in the coatings can be achieved through the analyses of nanoindentation force-displacement curves. Differences in the crack resistance of oxynitrides are more noticeable under dynamic loadings. Furthermore, coatings with a moderate value of oxygen content appear most promising in terms of mechanical and tribological behavior as well as crack resistance among the oxynitrides under investigation.

High temperature coefficient of resistance and low noise tungsten oxide doped amorphous vanadium oxide thin films for microbolometer applications

In this study, we report tungsten oxide (WO3) doped vanadium target in order to sputter amorphous vanadium tungsten oxide (a-VWOx) thin films by reactive direct-current magnetron sputtering technique. No post annealing and post oxidation steps were applied to improve bolometric properties. Thin films with high temperature coefficient of resistance, up to 3.02%/K, were prepared with resistivity range of 1–10 Ω cm thereby controlling the oxygen flow rate and sputtering conditions. Thin film composition was determined using X-ray photoelectron spectroscopy analysis which showed that the film has a mixed phase of V2O5, VO2 and V2O3. The noise level of the deposited film at 20 Hz was calculated as 1.9 × 10−15 V2/Hz from the noise spectrum density analysis. This noise level was found out to be comparable to the literature for VOx films deposited by ion beam deposition technique.

Advanced Micromorphology Analysis of Cu/Fe NPs Thin Films

In this work, an advanced analysis of Cu/Fe NPs thin films using atomic force microscopy (AFM) has been discussed to characterize at nanoscale 3-D surface microtexture. Samples of Cu/Fe thin films were fabricated by Direct Current-Magnetron Sputtering technique with two controlled thicknesses (group I: Cu 55 nm/Fe 55 nm and group II: Cu 55 nm/Fe 70 nm) in specific conditions of pressure and power. The results obtained from experimental measurements suggested that the surface of group I has the lowest values for fractal dimension (D = 2.28 ± 0.01) and root mean square height (Sq = 4.40 ± 0.1 nm); while the highest values for fractal dimension (D = 2.31 ± 0.01) and root mean square height (Sq = 4.67 ± 0.1 nm) were found in group II. Stereometric and fractal analyses applied for thin films are modern tools for accurate quantitative morphometric characterisation.

Effect of Nitrogen Flow Ratio on Composition, Microstructure, and Mechanical Properties of Cr-B-O-N Films Deposited by Pulsed Direct Current Magnetron Sputtering.

Nano-crystalline CrB₂ and Cr-B-O-N films with various nitrogen flow ratios were deposited using a pulsed direct current (PDC) magnetron sputtering technique. By means of electron probe micro-analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy, the influences of the nitrogen flow ratio on the phase constituents and microstructures of CrB₂/Cr-B-O-N films were systematically investigated. Mechanical properties including the hardness and elastic modulus were explored by a nano-indentation tester. On increasing the nitrogen flow ratio, the N and O contents in films increased linearly and tended to become saturated, whereas the Cr and B contents decreased. With an increasing nitrogen flow ratio, the microstructure changed from a dense columnar structure to a bulky columnar structure, and then to a fine and stacked dense structure. Meanwhile, the deposition rate also changed with increasing nitrogen flow ratio, owing to the changes in structure. Crystalline phases were observed by the XRD and HRTEM analyses, consisting of several nanometer-size crystallites embedded in an amorphous matrix. The dramatically decreased hardness was attributed to the large fractional volume of the softer amorphous phase BN in films.

Oxidation effect on pool boiling critical heat flux enhancement of Cr-coated surface for accident-tolerant fuel cladding application

The oxidation of an accident-tolerant fuel (ATF) cladding alters the surface roughness, which, in turn, affects the capillary wicking characteristics and critical heat flux (CHF) during the boiling process. To evaluate the effect of oxidation on the boiling performance of ATF coating, this study fabricated Cr-coated surfaces by varying the substrate temperature, resulting in various sizes of deposited particulate nanostructures by using a direct-current magnetron sputtering technique. To consider the oxidation effect, sputtered test specimens were oxidized at 400 °C dry air for 20 days, forming a Cr2O3 oxide layer with a thickness of approximately 0.1 μm. Pool boiling CHF experiments were conducted in deionized water under atmospheric pressure. The resultant CHF on the fresh and oxidized Cr-coated surfaces was enhanced by up to 36% and 48%, respectively. A higher CHF enhancement was achieved with a lower substrate temperature during sputtering, which resulted in a higher nanoscale surface roughness. The spreading velocities on each specimen were measured through the characterization experiments of liquid droplet spreading, which can be interpreted as the capillary wicking momentum. The pool boiling CHF was predicted with spreading velocity and roughness parameters. The predicted CHF showed a good agreement with the measured CHF. This study suggests that the oxidation of Cr-coated ATF specimens has a positive effect on the enhanced CHF, which can be confirmed through the altered surface roughness and capillary wicking momentum.

High Temperature Wear Behavior of Titanium Nitride Coating Deposited Using High Power Impulse Magnetron Sputtering

Titanium nitride (TiN) coating has been used in various application as it gives excellent performance in many aspects. It has been proven to prolong machining tool life since the mid-1960s. Industrial deposition processes of TiN, including magnetron sputtering, arc ion plating, and chemical vapor depositions, have their individual advantages and limitations. Due to the rising demands of the dry machining technique, the massive amount of heat generated from the friction of cutting tools against the surface of a work piece has become the main issue to overcome. Oxidation of TiN, which occurs around 400 °C, puts a limit on the applications of the coatings. Comparing TiN tool coatings deposited by arc evaporation, the novel high-power impulse magnetron sputtering (HiPIMS) technology provides smoother film surface, denser structure and subsequent corrosion resistance. Therefore, this research aims to investigate the wear behavior of TiN thin film deposited by HiPIMS at high temperature. The influences of the coating properties on the wear resistance of coatings at high temperature are also investigated. The results show that the HiPIMS technique enables a denser epitaxial-grown TiN coating with higher surface hardness and adhesion in contrast with TiN coating deposited using direct current (DC) magnetron sputtering techniques, which provides a higher wear resistance.

Study on dynamic scaling of morphological evolution of TiO 2 film deposited with different O 2 /Ar flow ratio

With increasing O2/Ar flow ratio from 2/18 to 20/0, TiO2 films were deposited by the direct current pulsed magnetron sputtering technique. The influence of O2/Ar flow ratio on plasma properties was discussed, which controlled the growth behaviour of TiO2 film. The growth behaviour influenced the value of roughness exponent α of TiO2 film, which reflected the dynamic scaling of the morphological evolution of TiO2 film. Finally, the relation between the dynamic scaling of the morphological evolution of TiO2 film and O2/Ar flow ratio was discussed systematically. The results indicate that with the other parameters constant, the growth behaviour of TiO2 film is dominated by O2/Ar flow ratio. By increasing O2/Ar flow ratio from 2/18 up to 6/14, the growth behaviour of TiO2 film transforms from the shadowing effect controlling to diffuse effect controlling, which results in the density of island structure on TiO2 film surface decreases, the size of island structure on TiO2 film surface increases, and the roughness exponent α of film decreases. When O2/Ar flow ratio exceeds 6/14, the density of island structure on TiO2 film surface remains constant. In this situation, the crystallographic orientation effect controls the growth behaviour of TiO2 film, which increases roughness exponent α.

Effects of environmental exposures on carbon fiber epoxy composites protected by metallic thin films

Carbon fiber epoxy composites have a wide range of applications in aerospace, construction, and automotive industries due to their good mechanical properties and lightweight characteristics. Carbon fiber epoxy composite structures are typically intended for service in corrosive and hostile environmental conditions. Therefore, development of coatings which are able to protect carbon fiber epoxy composite laminates against prolonged and harsh environmental conditions such as ultraviolet radiation and moisture deems critical. This paper offers a novel method for environmental protection of fiber-reinforced polymer composites by applying thin metallic films on composites' surface as coating materials. In order to investigate the protective properties of metallic thin films, copper and aluminum coatings were deposited on the surface of carbon fiber epoxy specimens by using direct current magnetron-sputtering technique, and then mechanical properties and surface morphology of specimens were monitored during the course of accelerated environmental exposure. Both metallic coatings showed good adhesion to carbon fiber epoxy samples during environmental aging and provided protection for the specimens' surface against environmental degradation. The correlation between flexural properties and surface morphology of carbon fiber epoxy specimens is also presented.

Structural and magnetic properties of stoichiometric Co4N epitaxial thin films

In this work, we studied the pathways for formation of stoichiometric \tcn~thin films. Polycrystalline and epitaxial \tcn~films were prepared using reactive direct current magnetron (dcMS) sputtering technique. A systematic variation in the substrate temperature (\Ts) during the dcMS process reveals that the lattice parameter (LP) decreases as \Ts~increases. We found that nearly stoichiometric \tcn~films can be obtained when \Ts~= 300\,K. However, they emerge from the transient state of Co target ($\phi$3\,inch). By reducing the target size to $\phi$1\,inch, now the \tcn~phase formation takes place from the metallic state of Co target. In this case, LP of \tcn~film comes out to be $\sim$99\p~of the value expected for \tcn. This is the largest value of LP found so far for \tcn. The pathways achieved for formation of polycrystalline \tcn~were adopted to grow an epitaxial \tcn~film, which shows four fold magnetic anisotropy in magneto-optic Kerr effect measurements. Detailed characterization using secondary ion mass spectroscopy indicates that N diffuses out when \Ts~is raised even to 400\,K. Measurement of electronic structure using x-ray photoelectron spectroscopy and x-ray absorption spectroscopy further confirms it. Magnetization measurements using bulk magnetization and polarized neutron reflectivity show that the saturation magnetization of stoichiometric \tcn~film is even larger than pure Co. Since all our measurements indicated that N could be diffusing out, when \tcn~films are grown at high \Ts, we did actual N self-diffusion measurements in a CoN sample and found that N self-diffusion was indeed substantially higher. The outcome of this work clearly shows that the \tcn~films grown prior to this work were always N deficient and the pathways for formation of a stoichiometric \tcn~have been achieved.

Efficacy of annealing and fabrication parameters on photo-response of SiGe in TiO2 matrix

SiGe nanoparticles dispersed in a dielectric matrix exhibit properties different from those of bulk and have shown great potential in devices for application in advanced optoelectronics. Annealing is a common fabrication step used to increase crystallinity and to form nanoparticles in such a system. A frequent downside of such annealing treatment is the formation of insulating SiO2 layer at the matrix/SiGe interface, degrading the optical properties of the structure. An annealing process that could bypass this downside would therefore be of great interest. In this work, a short-time furnace annealing of a SiGe/TiO2 system is applied to obtain SiGe nanoparticles without formation of the undesired SiO2 layer between the dielectric matrix (TiO2) and SiGe. The structures were prepared by depositing alternate layers of TiO2 and SiGe films, using direct-current magnetron sputtering technique. A wide range spectral response with a response-threshold up to ∼1300 nm was obtained, accompanied with an increase in photo-response of more than two-orders of magnitude. Scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy and grazing incidence x-ray diffraction were used to analyze the morphological changes in respective structures. Photoconductive properties were studied by measuring photocurrent spectra using applied dc-voltages at various temperatures.

Effect of Al Layer on Oxidation Behavior of NbCrAl Coating

NbCrAl coatings in the presence or absence of Al outer layer were prepared on C103 Nb based alloy and alumina substrate by direct current magnetron sputtering technique. The oxidation performance of coating systems was evaluated by isothermal oxidation tests. The element diffusion and oxidation behavior of the coating systems were investigated. The results indicate that the mass gains of NbCrAl and Al/NbCrAl coatings are 2.02 mg/cm2 and 0.79 mg/cm2 at 1 000 °C for short time. Al/NbCrAl coatings exhibit more effective protection than NbCrAl coatings. The addition of Al layer can improve the oxidation resistance of NbCrAl coatings, which is attributed to the Al layer offering enough Al content to react with oxygen to form a continuous and dense Al2O3 scale on NbCrAl coating and it can inhibit the further internal oxidation.