Dual Magnetron Sputtering Research Articles

Effect of photon annealing and cryogenic temperature on the microstructure, optical and electrophysical properties of Mo thin films

Mo films were deposited on a polyimide substrate by dual magnetron sputtering in an UniCoad 200 vacuum unit with an unbalanced magnetic system. The dependence of the characteristics of the obtained Mo films on photon annealing and cryogenic temperature was studied. The photonic annealing of Mo films was carried out at temperatures of 200 °C and 300 °C. For cooling Mo films, liquid nitrogen was used (t = -190°С). The characteristics of the films were investigated using X-ray diffraction, scanning electron microscopy and scanning probe microscopy. The results are presented on the change in specific electrical resistance, diffuse reflection spectra and adhesion strength of Mo films. It is shown that photon annealing at different temperatures does not affect the intensity of the X-ray diffractogram peaks of the Mo coating. After exposure, at a cryogenic temperature, an insignificant change in the X-ray diffractogram occurs, a shift of the diffractogram peak (110) is observed to large angles 2θ from 40.72° to 40.89°. The obtained Mo coating has a columnar structure in the form of tightly packed polycrystallites, oriented perpendicular to the substrate of the polyimide film. Mo coating on a polyimide substrate is resistant to sudden thermal exposure at temperatures not higher than 300 °C. Processing the resulting coating with liquid nitrogen leads to strong cracking of the Mo coating. At the same time, on samples with a coating thickness of 380–400 nm, exfoliation of the Mo coating, in the place of fracture, is not observed. The adhesive strength of the Mo coating with a polyimide film is quite high – 1.11 ± 0.05 GPa. Photon annealing does not reduce the adhesive strength of the Mo coating. The Mo film under conditions of cryogenic temperature (0.89 ± 0.08 GPa) has the worst adhesion strength.

Fabrication and characterization of nanocomposite films Al, Cu/Al and Cr/Al formed on polyimide substrate

The paper presents data on the application of a coating of Al on a polyimide substrate by the method of dual magnetron sputtering. The possibility of increasing the adhesion strength of Al coatings with polyimide by sputtering an intermediate layer of Cu and Cr is considered. The initial surface of the fabricated Al, Cu/Al and Cr/Al nanocomposite films was studied using electron scanning microscopy, and data on the surface resistance of the films and their adhesion strength with a polyimide substrate are presented. Energy-dispersion analysis showed that the coatings of Al, Cu/Al and Cr/Al nanocomposite films do not contain impurity atoms, which is also confirmed by the results of X-ray phase analysis. It is established that it is possible to obtain stable electrophysical characteristics of the surface with the following thickness of the intermediate layers: Cu - more than 200 nm and Cr - more than 113 nm. The deposition of nanocomposite films on a polyimide substrate reduces its surface resistance by more than 20 orders of magnitude. The adhesive strength of nanocomposite films with a polyimide substrate was studied. The best adhesion strength is provided by a polyimide/Cr/Al sample of 3.1 GPa.

Nanostructure of Rutile TiO<sub>2</sub> Thin Films Prepared on Unheated Substrate by Dual Cathode DC Unbalanced Magnetron Sputtering

In this work, structural and optical properties of the TiO2 films deposited on unheated substrates by dual cathode dc unbalanced magnetron sputtering at long substrate-target distance (ds-t) were studied. Titanium dioxide (TiO2) thin films were deposited on unheated Si (110) wafers, glass slides and carbon coated copper grids at different substrate to target (ds-t) distances. The structural properties of TiO2 thin films were characterized by X-ray diffraction (XRD) and transmission electron microcopy (TEM) with selected-area electron diffraction (SAED), surface morphology using atomic force microscopy (AFM) and optical transmission spectra using a spectrophotometer. XRD results show that TiO2 films deposited at various ds-t distances have only rutile crystal structure. The crystallinity and thickness of the films increased while the roughness decreased with decreasing ds-t distance. The refractive indices of the deposited films were found to be in the range of 2.51 - 2.82 and increased with decreasing ds-t distance.

Synthesis and characterization of (Ti1-xAlx)B2+Δ thin films from combinatorial magnetron sputtering

(Ti1-xAlx)B2+Δ films with a lateral composition gradient of x = [0.30–0.66] and Δ = [0.07–1.22] were deposited on an Al2O3 wafer by dual magnetron sputtering at 400 °C from sintered TiB2 and AlB2 targets. Composition analysis indicates that higher Ti:Al ratios favor overstoichiometry in B and a reduced incorporation of O. Transmission electron microscopy reveals distinctly different microstructures of Ti- and Al-rich compositions, with formation of characteristic conical growth features for the latter along with a lower degree of crystallinity and significantly less tissue phase from B segregation at the grain boundaries. For Al-rich films, phase separation into Ti- and Al-rich diboride nanometer-size domains is observed and interpreted as surface-initiated spinodal decomposition. The hardness of the films ranges from 14 to 28 GPa, where the higher values were obtained for the Ti-rich regions of the metal boride.

Influence of Annealing Temperature on the Microstructure and Morphology of TiN Films Synthesized by Dual Magnetron Sputtering

TiN films synthesized on leucosapphire substrates by dual magnetron sputtering have been annealed in vacuum at 600, 700, 800, and 900°C for 2 min. The microstructure and morphology of the films have been studied by X-ray diffraction and scanning electron microscopy at different temperatures. It has been found that annealing changes the microstructure, texture, grain size, and surface roughness of the TiN films.

Improved performance of thermochromic VO2/SiO2 coatings prepared by low-temperature pulsed reactive magnetron sputtering: Prediction and experimental verification

The paper deals with thermochromic VO2/SiO2 coatings prepared by low-temperature pulsed reactive magnetron sputtering on conventional soda-lime glass substrates without any substrate bias and without any interlayer. Thermochromic VO2 layers were deposited using reactive high-power impulse magnetron sputtering with a pulsed O2 flow control at a substrate surface temperature of 300 °C. Antireflection SiO2 layers were deposited using mid-frequency bipolar dual magnetron sputtering onto the top of VO2 layers at a surface temperature below 35 °C in order to improve the optical and mechanical performance. We focus on the dependence of the luminous transmittance (Tlum) and the modulation of the solar transmittance (ΔTsol) on the SiO2 layer thickness. The measured dependencies are in good agreement with those predicted using properties of pure VO2 layers measured by spectroscopic ellipsometry. Two different VO2 layer thicknesses (30 and 88 nm) have been used to demonstrate the tradeoff between Tlum and ΔTsol. We show an improvement due to the SiO2 overlayer of up to 16% (from 40.3% to 56.3%) for Tlum measured at 25 °C and up to 2.6% (from 7.7% to 10.3%) for ΔTsol. The results are important for the design and low-temperature fabrication of high-performance durable thermochromic VO2-based coatings for smart window applications.

Effect of the addition of Si into V2O5 coatings: Structure and tribo-mechanical properties

Vanadium oxide (V2O5) is one of the lubricious oxides with the potential to be used as a solid lubricant at elevated temperatures. However, the material itself is not hard wear-resistant, so most of the research has focused on adding V into hard nitride coatings that could lead to the formation of a self-lubricating V2O5 layer when heated. The other possible solution, which has been less studied, is to look for mechanisms to enhance the hardness of the oxide coating. In this research, we investigate the effect of the addition of Si into the V2O5 coatings, aiming to find conditions that lead to enhance hardness and/or reduced wear while keeping the high temperature lubricity of the V2O5 structure. For this, Si modified V2O5 coatings were deposited using a dual magnetron sputtering system. The results showed that small additions of Si (<2.0 at%) improved the hardness of the V2O5 coatings up to 5 times while keeping the same temperature dependence of the coefficient of friction than V2O5. Dry sliding experiments using the pin-on-disc configuration against silicon nitride balls were performed at 25, 300 and 600 °C. Wear factors in the 10−7 mm3/Nm range were obtained, indicating a good wear resistance. Further addition of Si into the V2O5 structure led to a loss of the crystalline ordering and a significant reduction in the hardness.

Stabilization of tetragonal ZrO2 by oxygen plasma treatment of sputtered ZrCu and ZrAl thin films

The stabilization of tetragonal zirconium dioxide (zirconia) by doping at room temperature has already been carried out with dopant materials like Y or Mg. Also alternative dopants like Al and Cu have been investigated using reactive sputtering processes at elevated temperatures with oxygen as a reactive gas. In the present work we investigate if stabilization is possible by dopants like Al and Cu which are added by means of non-reactive sputtering in a dual cathode magnetron sputtering device. Because it is expected that the stabilization depends on the dopant concentration, the Zr coatings were produced with a dopant gradient. So it was possible to investigate many different compositions with only few samples. This dopant gradient could be produced with a modification of the substrate holder in the sputtering chamber where a small wall partially shadows the vapor beam of the dopant. After production of the metallic ZrAl and ZrCu samples, first their chemical composition was determined by energy dispersive X-ray spectroscopy in a scanning electron microscope. Then they were treated with oxygen plasma. Depth profiles were recorded by Auger electron spectroscopy to investigate the progress of the oxidation. For crystallographic analysis X-ray diffraction was used. The surface morphology was measured with an atomic force microscope.The results show that the stabilization worked successfully with Cu while for Al no formation of the tetragonal phase was observed and the films remained essentially amorphous. The results show that oxygen plasma treatment is a viable and fast way to transform doped metallic Zr films into tetragonal Zirconia.

Influences of Target Peak Current Density on the Microstructure and Mechanical Properties of TiN Films Deposited by Dual Pulsed Power Magnetron Sputtering

Influences of Target Peak Current Density on the Microstructure and Mechanical Properties of TiN Films Deposited by Dual Pulsed Power Magnetron Sputtering

Surface Modification of C17200 Copper-Beryllium Alloy by Plasma Nitriding of Cu-Ti Gradient Film

In the present work, a copper-titanium film of gradient composition was firstly fabricated by the dual magnetron sputtering through power control and plasma nitriding of the film was then conducted to modify C17200 Cu alloy. The results showed that the prepared gradient Cu-Ti film by magnetron sputtering was amorphous. After plasma nitriding at 650 °C, crystalline Cu-Ti intermetallics appeared in the multi-phase coating, including CuTi2, Cu3Ti, Cu3Ti2 and CuTi. Moreover, even though the plasma nitriding duration of the gradient Cu-Ti film was only 0.5 h, the mechanical properties of the modified Cu surface were obviously improved, with the surface hardness enhanced to be 417 HV0.01, the wear rate to be 0.32 × 10−14 m3/Nm and the friction coefficient to be 0.075 at the load of 10 N, which are all more excellent than the C17200 Cu alloy. In addition, the wear mechanism also changed from adhesion wear for C17200 Cu substrate to abrasive wear for the modified surface.

Uniform sputter deposition of high-quality epitaxial complex oxide thin films

Uniform deposition of high-quality epitaxial complex oxide thin films over a large area is desirable not only for the large scale fabrication of oxide electronics but also for preparing multiple samples with the same growth conditions for various characterization techniques. However, it is particularly challenging to grow uniform thin films of multicomponent oxide systems containing volatile species such as Pb and Bi. By combining a misaligned parallel dual planar magnetron sputtering technique with substrate rotation, the authors have grown uniform epitaxial thin films piezoelectric 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 and multiferroic monodomain BiFeO3 with high-deposition rates over a 2 in. diameter area. These films have excellent uniformity of thickness, stoichiometric compositions, and electrical properties. This technique can be scaled to larger deposition areas by using larger sputtering targets and widely applied to various multicomponent complex oxide thin film heterostructures.

Characteristics of InZnSnO Thin Films Deposited by Dual Magnetron Sputtering for Thin Films Transistors

Characteristics of InZnSnO Thin Films Deposited by Dual Magnetron Sputtering for Thin Films Transistors

Functional Multi-Nanolayer Coatings of Amorphous Carbon/Tungsten Carbide with Exceptional Mechanical Durability and Corrosion Resistance

A novel functional multilayer coating with periodically stacked nanolayers of amorphous carbon (a:C)/tungsten carbide (WC) and an adhesion layer of chromium (Cr) was deposited on 304 stainless steel using a dual magnetron sputtering technique. Through process optimization, highly densified coatings with high elasticity and shear modulus, excellent wear resistance, and minimal susceptibility to corrosive and caustic media could be acquired. The structural and mechanical properties of the optimized coatings were studied in detail using a variety of analytical techniques. Furthermore, finite element method simulations indicated that the stress generated due to contact against a steel ball was distributed well within the coating, which allowed the stresses to be lower than the yield threshold of the coating. Thus, an ultralow wear rate of ∼10-12mm3/N mm could be achieved in dry sliding conditions under relatively high Hertzian contact pressures of ∼0.4-0.9 GPa. The amorphous and pinhole-free structure of the individual layers, sufficient number of pairs, and the relatively dense stacked layers resulted in significant polarization resistance (Z″ = 5.5 × 106 Ω cm2) and increased the corrosion resistance of the coating by 10-fold compared to that of recently reported corrosion-resistant coatings.

Reactive bipolar pulsed dual magnetron sputtering of ZrN films: The effect of duty cycle

Zirconium nitride (ZrN) coatings, due to their inherent high hardness, wear and corrosion resistance, as well as the golden color, can be attractive for a wide range of applications, such as mechanical, optical, decorative and biomedical devices. Reactive Bipolar Pulsed Dual Magnetron Sputtering (BPDMS) operating in mid-frequency range is a powerful technique for the deposition of dense coatings, free from morphological defects, at high deposition rate. In fact, the use of mid-frequency voltage reversals allows suppressing arcs and, as a consequence, stabilizing the reactive sputtering process. Despite the success of the dual bipolar process, there are many aspects of this complex process that are not yet well understood, such as the influence of the target voltage waveforms and plasma parameters on the film growth. In order to fill this lack of knowledge, ZrN films were deposited by BPDMS with different voltage waveforms on the Zr targets and the influence of these deposition parameters on the films’ stoichiometry as well as on their structural and mechanical properties is investigated in this paper. In particular, it was found that, for duty cycle values below 33%, the hardness of the coating increases up to 31GPa. The analysis of the chemical composition, performed by XPS, detects an almost constant value of stoichiometry along the depth-profile of each film and the N:Zr ratio increases from 1.06 to 1.20 as the duty cycle decreases. Therefore, when the N:Zr ratio is 1.06 we got a stoichiometric ZrN compound, while for N:Zr equal to 1.20 we obtained a lack of Zr atoms with respect to N atoms. Raman spectroscopy confirms the results of XPS analyzes, since it showed some features related to the structural disorder in the sample grown with the lowest duty cycle.

Characteristics of Ti Thin films and Application as a Working Electrode in TCO-Less Dye-Sensitized Solar Cells

The structural, electrical and optical properties of Ti thin films fabricated by dual magnetron sputtering were investigated under various film thicknesses. The fabricated Ti thin films exhibited uniform surfaces, crystallinity, various grain sizes, and with various film thicknesses. Also, the crystallinity and grain size of the Ti thin films increased with the increase of film thickness. The electrical properties of Ti thin films improved with the increase of film thickness. The results showed that the performance of TCO-less DSSC critically depended on the film thickness of the Ti working electrodes, due to the conductivity of Ti thin film. However, the maximum conversion efficiency of TCO-less DSSC was exhibited at the condition of 100 nm thickness due to the surface scattering of photons caused by the variation of grain size.

Sputter deposition of Titanium and Nickel thin films in radio frequency magnetron discharge characterized by optical emission spectroscopy and by Rutherford backscattering spectrometry

By using a homemade dual magnetron sputtering system, two combined investigations by Optical emission spectroscopy and by Rutherford backscattering spectrometry were performed on a Radio-Frequency discharge for Titanium and Nickel deposited in pure Argon gas. Line intensities of various species present in the plasma were compared to the Argon emission line I of 696.5nm for different gas pressure and power density values. The electron temperature was also determined from the collisional radiative model and then correlated to the gas pressure and the power density. It was found that the sputtering pressure alters the spectrum intensity of Nickel, but has no obvious effect on that of Titanium during sputtering. The variation of average deposition rate as a function of gas pressure was experimentally determined via the Rutherford backscattering technique and then correlated to the variation of electron temperature of (Titanium-Argon) and (Nickel-Argon) discharges versus gas pressure.

Influences of Interfacial Carbonization on the Structure and Mechanical Properties of Multilayered Cr-Containing Diamond-Like Carbon Films

Regarding metal-containing diamond-like carbon (Me-DLC) multilayered films, current research has focused on the influences of macroelements in the transition layer on the mechanical properties. The understanding of influences of microinterfacial structures on the mechanical properties is far from enough. One example is the structure pattern due to carbonation around the layer-to-layer interfaces in the Me-DLC films. In this work, multilayered Cr-DLC films with three modulation periods (Λ) were deposited using midfrequency dual-magnetron sputtering, and the film microstructures and mechanical properties were investigated. Along with changes in Λ, interfacial carbonization induces microstructure changes, and the microstructures include carbon bond, phase compositions, and internal stresses. The microstructure changes affect the mechanical properties, including hardness, elastic modulus, fracture toughness, and adhesion. The results reveal that variation of mechanical properties is involved with the influenc...

Core–shell formation in self-induced InAlN nanorods

We have examined the early stages of self-induced InAlN core–shell nanorod (NR) formation processes on amorphous carbon substrates in plan-view geometry by means of transmission electron microscopy methods. The results show that the grown structure phase separates during the initial moments of deposition into a majority of Al-rich InAlN and a minority of In-enriched InAlN islands. The islands possess polygonal shapes and are mainly oriented along a crystallographic c-axis. The growth proceeds with densification and coalescence of the In-enriched islands, resulting in a base for the In-enriched NR cores with shape transformation to hexagonal. The Al-rich shell formation around such early cores is observed at this stage. The matured core–shell structure grows axially and radially, eventually reaching a steady growth state which is dominated by the axial NR growth. We discuss the NR formation mechanism by considering the adatom surface kinetics, island surface energy, phase separation of InAlN alloys, and incoming flux directions during dual magnetron sputter epitaxy.

The effect of heating rate on the phase transformation of Ni/Ti multilayer thin films

Ni/Ti multilayer thin films prepared by dual cathode magnetron sputtering were annealed in vacuum at different heating rates. The structural evolution of the multilayer thin films with nanometric modulation periods was studied in-situ by x-ray diffraction using synchrotron radiation. Independently of the multilayer period, a single step rapid reaction occurs at temperatures above 300 °C with the formation of the B2-NiTi austenite phase. The transformation temperature is inversely proportional to the multilayers period (higher temperature for shorter period - 12 nm) and to the heating rate (lower temperature for faster heating rates).

Silicon induced stability and mobility of indium zinc oxide based bilayer thin film transistors

Indium zinc oxide (IZO), silicon containing IZO, and IZO/IZO:Si bilayer thin films have been prepared by dual radio frequency magnetron sputtering on glass and SiO2/Si substrates for studying their chemical compositions and electrical characteristics in order to ascertain reliability for thin film transistor (TFT) applications. An attempt is therefore made here to fabricate single IZO and IZO/IZO:Si bilayer TFTs to study the effect of film thickness, silicon incorporation, and bilayer active channel on device performance and negative bias illumination stress (NBIS) stability. TFTs with increasing single active IZO layer thickness exhibit decrease in carrier mobility but steady improvement in NBIS; the best values being μFE ∼ 27.0, 22.0 cm2/Vs and ΔVth ∼ −13.00, −6.75 V for a channel thickness of 7 and 27 nm, respectively. While silicon incorporation is shown to reduce the mobility somewhat, it raises the stability markedly (ΔVth ∼ −1.20 V). Further, IZO (7 nm)/IZO:Si (27 nm) bilayer based TFTs display useful characteristics (field effect mobility, μFE = 15.3 cm2/Vs and NBIS value, ΔVth =−0.75 V) for their application in transparent electronics.