DC Reactive Sputtering Research Articles

Effect of nitrogen partial pressure on the structural and mechanical properties of (MoNbTaW)N thin films deposited by DC magnetron sputtering

This study investigates the influence of nitrogen partial pressure on the microstructure, crystal structure, chemical bonding, and mechanical properties of (MoNbTaW)N films deposited on silicon substrates via DC reactive sputtering. The depositions were carried out at room temperature from a MoNbTaW alloy target at 0.6 Pa by varying nitrogen partial pressure between 0% and 50%. The surface morphology, crystal structure, bonding characteristics, and mechanical properties were studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and nanoindentation. SEM and AFM findings reveal significant morphological changes from lenticularlike structures to fine-grain structures as nitrogen partial pressure increases from 0% to 50%, with feature size decreasing from 12 to 8 nm. XRD analysis confirms a crystalline structure in all films, transforming from body-centred cubic to face-centred cubic, occurring between 16% and 33% nitrogen partial pressure. XPS analysis confirms the formation of metal–nitrogen (Me–N) bonds through binding energy shifts. Despite these structural changes, no significant variations in hardness and film modulus were observed with changes in nitrogen partial pressure, which can be attributed to weaker p(N)-d(TM) interactions. The study underscores nitrogen's crucial role in altering microstructure and crystal structure, while the strength of the Me–N bond limits its effect on mechanical properties.

DC reactive sputtering synthesis of titanium nitride coatings on titanium for biomedical applications

DC reactive sputtering synthesis of titanium nitride coatings on titanium for biomedical applications

Enhancement of optoelectronic properties of Vanadium nitride/porous silicon heterojunction photodetector prepared by electrochemical etching and reactive DC sputtering

In this work, vanadium nitride (VN) thin films were deposited on porous silicon using the DC sputtering technique. The porous silicon was prepared using the electrochemical etching method at various current densities. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, UV–visible spectrometry, and photoluminescence (PL) spectroscopy were used to study the structural, morphological, chemical, and optical characteristics of the vanadium nitride and porous silicon. X-ray diffraction studies showed that the deposited vanadium nitride film was crystalline in nature with a cubic structure. The VN particles were found to be embedded inside the pores of the porous silicon. The crystallite size of the VN film was 8 nm. The optical absorption results showed that the optical energy gap of vanadium nitride was 2.98 eV. The photoluminescence spectra revealed the presence of four emission peaks located at 441, 496, 541, and 720 nm. The electrical properties of the VN/PSi heterojunction, including dark and illuminated current-voltage characteristics as a function of etching current density, were investigated. The best ideality factor was 3.1 for heterojunction prepared at a current density of 8 mA/cm2. A responsivity of 3.7 A/W and a detectivity of 6.5 × 1011 Jones at 500 nm were found for the photodetector fabricated at a current density of 8 mA/cm2. The (I-t) response of the photodetectors were determined.

Photocatalytic activity of TiO2:TiN nanocomposite films prepared by DC reactive sputtering technique for air purification

This study concerns the production of advanced materials and a novel technique for enhancing photocatalytic efficiency, focusing specifically on the purification of air contaminated with methane gas. Titanium dioxide:Titanium nitride (TiO2/TiN) nanocomposite films were prepared by dc reactive magnetron sputtering of highly-pure titanium sheet in presence of oxygen and nitrogen as reactive gases with optimized mixing ratios to produce the composite structures. The structural, morphological, and optical characteristics of the prepared nanocomposites were determined and analyzed. The primary goal of this study was to enhance the photocatalytic activity of such nanocomposites against methane gas pollution. It is observed that increasing the nitrogen content in the TiO2:TiN nanocomposite structure led to notable improvements in photocatalytic efficiency. Specifically, when these nanocomposites were subjected to a UV light, they exhibited enhanced photocatalytic activity in the removal of methane gas from the surrounding air, which demonstrates a direct correlation with increased nitrogen (N) content in the composite structure. These nanocomposites are reasonably promising in removing harmful gases and pollutants present in indoor and outdoor environments. This exploration not only sheds light on the remarkable potential of TiO2:TiN nanocomposites for air purification but also highlights the importance of innovative techniques, such as dc reactive magnetron sputtering in the field of materials science and engineering as well as in environmental remediation.

Effect of nitrogen content on the structure and superconductivity of reactive sputtered NbTiN thin films

In this research, we have studied the structural and electrical properties of NbTiN films deposited on MgO and SiO2/Si substrates by reactive dc sputtering. The formation of stoichiometric NbTiN is very sensitive to N concentration and can be easily adjusted by changing the discharge current and Ar: N2 ratio along the current–voltage curves (IVCs) of the NbTi target. Excessive or insufficient N concentration in NbTiN leads to sublattice expansion or distortion, resulting in a decrease in critical temperature T c. At Ar: N2 ratio of 30:4 and discharge current of 2.2 A, T c as high as 15.8 K and 15.3 K has been obtained for 200 nm thick NbTiN/MgO and NbTiN/SiO2/Si samples, respectively. In addition, the critical density J c of the 4 μm-wide and 7 nm-thick NbTiN film grown on MgO substrate at 2 K reaches 19.2 MA cm−2, which is approximately twice as high as the 10.9 MA cm−2 of the same-sized NbTiN film grown on SiO2/Si substrate. Therefore, by further fine-tuning the N concentration in combination with the IVCs of the target, high-quality stoichiometric NbTiN can be obtained.

Synthesis and Characterization of Nickel Ferrite Nanostructures by DC Reactive Sputtering Technique Using New Target Configuration

Synthesis and Characterization of Nickel Ferrite Nanostructures by DC Reactive Sputtering Technique Using New Target Configuration

Influence of underlayer roughness on the properties of Sc0.4Al0.6N thin films prepared via sputter deposition

Abstract A ScAlN thin film is one of the key materials of MEMS and high-frequency filters used in new-generation communication devices. Piezoelectricity can be improved by increasing Sc concentration. However, abnormal grains often appear at high Sc concentrations, degrading crystallinity and piezoelectricity. Herein, we demonstrated that underlayer roughness considerably affects the emergence of abnormal grains in a Sc0.4Al0.6N thin film formed via reactive DC sputtering. Dry etching with Ar plasma can effectively reduce the surface roughness of amorphous SiN and polycrystalline Si. Sc0.4Al0.6N thin films deposited on amorphous SiN and polycrystalline Si with sufficient flat surfaces exhibited a low density of abnormal grains, high crystallinity and piezoelectricity, and low loss tangent. Moreover, such high-quality thin films were obtained on a borophosphosilicate glass flattened using a reflow process without Ar etching. Therefore, underlayer roughness played an important role. The findings can help enable the large-scale production of highly doped ScAlN thin films.

NbC thin films via reactive DC sputtering in a CH4/Ar atmosphere

We have demonstrated the growth of NbC-Amorphous C films that manifest a well-known nanocomposite structure (Klages and Memming, 1990; Nedfors et al., 2011; Sala et al., 2021). The films were deposited using reactive DC sputtering in a CH4/Ar atmosphere using an insulating substrate near room temperature. A metallic Nb sputtering target was sputtered in an argon/CH4 atmosphere with a pressure range of 5.9 to 8.5 mTorr as the CH4 flow was also varied. Crystalline NbC films were deposited at room temperature at the lowest CH4 flow rate. The films exhibited ohmic electrical response at room temperature. The DC electrical resistivity scaled almost 4 orders of magnitude from 4.39 × 10−4 Ω-cm to 1.08 × 10−1 Ω-cm through changes in CH4 flow rates and the resultant C content of the films. The large variation in resistivity cannot be attributed to the changes in sample composition, e.g. volumetric mixing. It is postulated from XRD and TEM results that the large change in resistivity is due to the decreasing NbC crystallite size with increasing CH4. This leads to additional three-dimensional nanoscale intragranular interfaces and results in increased resistivity. X-ray reflectivity measurements were conducted, and the modelled film density was found to match the expected density for the film compositions as measured using X-ray photoelectron spectroscopy. Elastic recoil detection analysis (ERDA) was used to quantify H content of the films. The H content increased from 5.5 to 22 atomic percent with corresponding increase in CH4 flow. Transmission electron microscopy utilizing precession electron diffraction (PED) was conducted and showed a strong dependence of crystallinity on CH4 flow. A multilayer layer sample with varying CH4 flowrates was examined with TEM and showed that films were amorphous in nature for flow rates above 10 SCCM CH4; in agreement with XRD results.

Metal oxide-based gas sensor array for VOCs determination in complex mixtures using machine learning

Detection of volatile organic compounds (VOCs) from the breath is becoming a viable route for the early detection of diseases non-invasively. This paper presents a sensor array of 3 component metal oxides that give maximal cross-sensitivity and can successfully use machine learning methods to identify four distinct VOCs in a mixture. The metal oxide sensor array comprises NiO-Au (ohmic), CuO-Au (Schottky), and ZnO–Au (Schottky) sensors made by the DC reactive sputtering method and having a film thickness of 80–100 nm. The NiO and CuO films have ultrafine particle sizes of < 50 nm and rough surface texture, while ZnO films consist of nanoscale platelets. This array was subjected to various VOC concentrations, including ethanol, acetone, toluene, and chloroform, one by one and in a pair/mix of gases. Thus, the response values show severe interference and departure from commonly observed power law behavior. The dataset obtained from individual gases and their mixtures were analyzed using multiple machine learning algorithms, such as Random Forest (RF), K-Nearest Neighbor (KNN), Decision Tree, Linear Regression, Logistic Regression, Naive Bayes, Linear Discriminant Analysis, Artificial Neural Network, and Support Vector Machine. KNN and RF have shown more than 99% accuracy in classifying different varying chemicals in the gas mixtures. In regression analysis, KNN has delivered the best results with an R2 value of more than 0.99 and LOD of 0.012 ppm, 0.015 ppm, 0.014 ppm, and 0.025 ppm for predicting the concentrations of acetone, toluene, ethanol, and chloroform, respectively, in complex mixtures. Therefore, it is demonstrated that the array utilizing the provided algorithms can classify and predict the concentrations of the four gases simultaneously for disease diagnosis and treatment monitoring.Graphical

Investigation of Fabrication Conditions and Acceleration of Crystallization of α&quot;-Fe16N2 Thin Film Fabricated by Pulsed DC Reactive Sputtering for High Density Magnetic Recording Media Application

Investigation of Fabrication Conditions and Acceleration of Crystallization of α&quot;-Fe₁₆N₂ Thin Film Fabricated by Pulsed DC Reactive Sputtering for High Density Magnetic Recording Media Application

DC reactive sputtering of ZnON thin films: band gap engineering and associated evolution of microstructures

Zinc oxynitride (ZnON) has recently emerged as a highly promising band gap-tunable semiconductor material for optoelectronic applications. In this study, a novel DC reactive sputtering protocol was developed to fabricate ZnON films with varying elemental concentrations, by precisely controlling the working pressure. The working pressure was varied from 0.004 mbar to 0.026 mbar.For working pressure greater than 1.6 × 10−3mbar, the mean free path of ions decrease, the sputtering rate decreases and the concentration of nitrogen in the films decreases. The band gap of the film obtained from UV Vis Spectroscopy initially decreases and reaches a minimum of 1.6 eV at a flow rate of 20 sccm of nitrogen, after which it drastically increases. The correlation between the micro structure and band gap was investigated. The initial alloy structure of the film was found to exist when the band gap was between 1.66 eV and 2.15 eV, beyond which, a distorted wurtzite structure began to emerge. At a band gap of 2.7 eV, the spectrum peaks indicated the coexistence of both alloy and wurtzite structures. With an increasing band gap, the wurtzite structure became dominant, completely replacing the alloy structure at 3.25 eV. This study revealed the existence of intermediate structures formed during the tuning of the band gap, which can have important implications for future research aimed at developing heterostructures and 2D superlattices for photonics applications.

Effect of Nb and V doped elements on the mechanical and tribological properties of CrYN coatings

One of the most promising approaches to enhancing the tribological properties of engineering coatings is to add transition elements to the structure. In this study, Nb-doped CrYN and V-doped CrYN thin films were deposited by pulsed DC reactive sputtering in a closed-field unbalanced magnetron sputtering (CFUBMS) system. The deposition parameters examined were target current (1, 1.5 and 2 A), deposition pressure (0.15, 0.25 and 0.35 Pa), pulse frequency (100, 200 and 350 kHz) and duty cycle (85 %, 70 % and 50 %). A Taguchi L9 orthogonal design was used to define the deposition process parameters for each doped film. The Nb and V-doped CrYN thin films were characterized in terms of their microstructure, thickness, composition, hardness and tribological properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), nanohardness and pin-on-disc testing, respectively. The bond strength between the substrate and the films (adhesion) was analyzed by scratch testing. For the Nb-doped thin films, a maximum hardness value of 21.4 GPa and the lowest friction coefficient of 0.36 were obtained. On the other hand, in the V-doped thin films, the maximum hardness value was 16.1 GPa, while the lowest friction coefficient obtained was 0.11. In addition, Nb-doped and V-doped CrYN thin films exhibited extraordinary adhesion properties. The effect of the selected deposition parameters (target current, pulse frequency, and duty cycle) in relation to the film thickness, hardness, and coefficient of friction properties of the Nb and V-doped CrYN thin films were investigated using the Taguchi approach and optimum operating conditions were identified and confirmed.

Fabrications of metal-insulator nanocomposite TiOx thin films and their dielectric properties

The nanocomposite titanium oxides (TiOX) films were grown on the glass substrate using the reactive DC sputtering method. A solid-state disproportionation process led to the development of a multi-phase structure, consisting of nanocrystalline dioxies (TiO2) and suboxides (TinO2n-1) embedded with an amorphous TiO2-δ matrix. As the plasma discharge impedance decreased during the sputtering growth, a sequence of TiO2 crystallites, sesquioxides (Ti2O3), and eventually monoxides (TiO) were formed. This progression came at the expense of compromising the quality of the TiO2 crystallites and resulted in the reduction of oxygen vacancies in the a-TiO2-δ matrix. Furthermore, the frequency-dependent impedance measurements revealed that the metal-insulator nanocomposite TiOx films containing TiO crystallites exhibited a remarkable permittivity above 106 in the frequency range of 102 ∼106 Hz. We believe that the observed colossal permittivity is primarily attributed to the interface polarization within the composite constituents, in addition to the electrode effects.

Morphology tuned plasmonic TiN nanostructures formed by angle-dependent sputtering process for SERS measurements

Nowadays, most SERS platforms are based on plasmonic metals like silver and gold. The current scientific achievement is to construct SERS non-metallic platform with SERS activity not worse than in case of standard metallic platforms. The prominent combination of opto-electronic properties of TiN (titanium nitride) makes it a promising alternative plasmonic material for noble metals. So far, the TiN nanostructures are widely tested in catalysis, especially in photocatalysis. Despite the TiN potential in SERS sensing applications, there are still several fundamental issues preventing its wide practical application. In this work, the surface morphology of TiN layers was tuned from planar 2D to a high aspect ratio 1D nanorod-like structures by industrially scalable normal and glancing angle deposition (GLAD) pulsed DC reactive sputtering. The morphology of formed samples was studied by SEM microscopy, while the crystallographic properties were examined by Raman and XRD method. The opto-electrical parameters measured by spectroscopic ellipsometry, and DRS spectroscopy revealed substantial changes in optical properties of the TiN films with the variation of glancing angle. This in turn opened the way for tailoring the surface plasmon resonance and hence for SERS activity.

Employment of Silicon Nitride Films Prepared by DC Reactive Sputtering Technique for Ion Release Applications

In this work, silicon nitride (Si3N4) thin films were deposited on metallic substrates (aluminium and titanium sheets) by the DC reactive sputtering technique using two different silicon targets (n-type and p-type Si wafers) as well as two Ar:N2 gas mixing ratios (50:50 and 70:30). The electrical conductivity of the metallic (aluminium and titanium) substrates was measured before and after the deposition of silicon nitride thin films on both surfaces of the substrates. The results obtained from this work showed that the deposited films, in general, reduced the electrical conductivity of the substrates, and the thin films prepared from n-type silicon targets using a 50:50 mixing ratio and deposited on both surfaces of a titanium substrate reduced the electrical conductivity of this substrate by 30%. This reduction in the release of ions from the coated metal substrate is attributed to the dielectric properties of the deposited silicon nitride thin films. This result is very important and applicable. This work represents the first attempt in Iraq to study such effects and may represent a good starting point for advanced studies in biomedical engineering.

Structural and Hardness Characteristics of Silicon Nitride Thin Films Deposited on Metallic Substrates by DC Reactive Sputtering Technique

Structural and Hardness Characteristics of Silicon Nitride Thin Films Deposited on Metallic Substrates by DC Reactive Sputtering Technique

Physical Properties of SnO2/WO3 Bilayers Prepared by Reactive DC Sputtering

The combination of transparent and conductive SnO2 with colored WO3 thin films has interesting uses in electrochromic windows, photovoltaic cells and photocatalytic systems, where the SnO2/WO3 bilayer can improve the device efficiency by increasing the charge separation and extending the energy range of photoexcitation. In this work, SnO2 and WO3 thin films were prepared by reactive DC sputtering from Sn and W targets, respectively. Single layers and bilayers deposited on glass substrates have been analyzed by X-ray diffraction, atomic force microscopy, spectrophotometry, and electrical measurements. SnO2 crystallizes in the cassiterite structure, whereas amorphous WO3 is obtained on bare and SnO2-coated glasses, showing higher surface roughness on the SnO2 layer. Different oxygen vacancy defects have been identified in WO3 by analyzing photoconductivity transients. The oxygen vacancy defects are responsible for the sub-bandgap absorption that causes coloration in the WO3 films. Regarding SnO2, it shows a high transmittance of about 90% in the visible and near-infrared spectral ranges.

Optoelectrical properties extraction using spectroscopic ellipsometry, in case of AZO thin films deposited by DC reactive sputtering in various oxygen concentration

Optoelectrical properties extraction using spectroscopic ellipsometry, in case of AZO thin films deposited by DC reactive sputtering in various oxygen concentration

Morphological, mechanical and antibacterial properties of Ti–Cu–N thin films deposited by sputtering DC

The problems associated with Stainless Steel 316 L (SS 316 L) orthopedic implants, when implanted in the human body, are infection, local inflammation, and the possibility of bacterial growth. In this study, SS 316 L was coated with copper-doped Titanium Nitride (Ti–Cu–N) using the DC Sputtering technique. This Ti–Cu–N film improved the antibacterial performance and mechanical properties of SS 316 L. The Ti–Cu–N films were deposited using reactive DC sputtering with an 80%:20% argon to nitrogen ratio. The source voltage and current were kept constant at 10 kV and 10 mA, respectively. X-Ray Diffraction (XRD) showed that the phases formed were TiN and Cu with FCC crystal structure. Results show that the surfaces of samples containing 44.34 wt% and 54.97 wt% Cu had antibacterial effectiveness against Staphylococcus aureus (S. Aureus). The highest hardness value of a Ti–Cu–N layer was 212.032 Vickers Hardness Number (VHN), which was an improvement of 36.63% on the raw material (155.18 VHN). Surface morphology analysis using SEM-EDS was performed on the samples before and after the antibacterial test to investigate the antibacterial mechanism of the surfaces of SS 316 L containing Ti–Cu–N against S. Aureus.

Influence of crystallinity and stoichiometry on the high temperature semiconductor-metal transition of lanthanum cobalt oxide deposited by reactive dc sputtering

Lanthanum cobalt oxide (LCO) has garnered growing interest in electronic switch applications based on its unique insulator to metal transition. A single-step high temperature deposition process was developed for thin film LCO via reactive dc magnetron sputtering, starting with exploration of target poisoning within the context of Berg's theory. By tracking target voltage on metal targets during reactive deposition, we reason that increasing inert gas flux to the target improves target hysteresis, thus increasing target lifetime. Furthermore, it is shown that the onset of the critical region of oxide deposition has a stronger dependence on reactive gas flow than on partial pressure and is found at approximately 1.5 sccm and 5 sccm oxygen flow rate for the La and Co targets, respectively. We subsequently probed substrate and stoichiometry influence on LCO film quality and electronic properties. Epitaxial (100) LaCoOx (Rq = 0.41 nm) films grown on lanthanum aluminate (LaAlO3) demonstrate similar reductions in resistivity over 300 K–623 K as polycrystalline LCO films on 4H–SiC and sapphire (Rq = 1.59, 2.36 nm respectively). However, La-heavy films, grown as La2.6CoO4.8, can demonstrate significantly steeper resistivity drops. Finally, we estimate the band gap collapse and insulator-metal transition of thin-film LCO over temperature by near-IR absorption.