Reactive Magnetron Sputter Deposition Research Articles

Solid-State Au Nanocone Arrays Substrate for Reliable SERS Profiling of Serum for Disease Diagnosis.

Surface-enhanced Raman scattering (SERS) is a widely used rapid and noninvasive method for detecting biological substances in serum samples and is commonly employed in disease screening and diagnosis. Solid-state nanoarray SERS substrates used in serum detection may cause spectral instability due to imperfections in the detection method. For the purpose of identifying optimal detection conditions, various dilution levels of the serum were tested in this study. The study found that a complete and stable serum SERS spectrum can be obtained when the serum is diluted by a factor of 50. The study reports the successful preparation of an Au nanocone array (Au NCA) plasmonic substrate with a uniform, controllable microstructure and high activity, achieved through a combination of PS colloidal sphere template-assisted reactive ion etching (RIE) process and magnetron sputtering deposition technology. Based on this substrate, a standard detection scheme was developed to obtain highly stable and repeatable serum SERS spectra. The study verified the reliability of the optimized serum detection scheme by comparing the SERS spectra of serum samples from healthy individuals and gastric cancer patients, and confirmed the potential benefits of the scheme for disease screening and diagnosis.

On the surface biasing effectiveness during reactive high-power impulse magnetron sputter deposition of zirconium dioxide

In this study, we investigate the effect of surface biasing during high-power impulse magnetron sputter deposition of non-conductive zirconium dioxide films on substrates with different capacitances. We employ reactive high-power impulse magnetron sputtering to deposit ZrO2 films using a circular Zr target in a pure oxygen atmosphere. The deposition experiments are conducted on two types of substrates: high-capacitance (thin thermally grown SiO2 on Si) and low-capacitance (soda-lime glass). By varying the time shift between the target voltage pulse and the negative substrate bias voltage pulse, we analyze the impact on the preferred crystal orientation of the deposited ZrO2 films and the deposition rate. We measure the current and voltage waveforms during the deposition process and utilize a surface charging model to understand the charging behavior of the growing film. Additionally, time- and energy-resolved ion mass spectra are measured to gain insights into the ion behavior during film growth. Our results demonstrate that energetic ion bombardment and appropriate timing of substrate biasing can influence the crystal orientation of ZrO2 films, favouring specific orientations over others. We also explain the different behavior observed on low- and high-capacitance substrates.

Characterization, mechanical and biomedical properties of titanium oxynitride coating

In this study, a titanium oxide-nitride coating was applied to 12Cr18Ni10Ti stainless biomedical steel through reactive magnetron sputtering deposition. The microstructure and chemical bond evolution during film sputtering was tested using different flow rates of oxygen and argon, namely N2/O2 ratios of 1, 1.5, and 2. The obtained samples were analysed by IR spectroscopy, SEM, XPS, and XRD. In addition, the nanoindentation procedure measured the hardness and elastic modulus of each coating. Oxynitride coatings exhibit nanocrystalline structures, where the nitride and oxide phases are in the unbound state. A nitrogen-rich sample demonstrated the crystalline structure of (110)-oriented rutile with 124 nm large clusters. However, with increased oxygen gas flow, the mixed rutile-anatase (111)-oriented phase became more pronounced with fragmented grains 25–27 nm in diameter. The nanoindentation test shows that titanium oxide hardness and deformation resistance depend on its microstructure and orientation. Cell culture experiments show that a coating deposited at regime N2/O2 = 1 allows efficient cell proliferation on pristine steel and other oxynitride samples. The findings of this work benefit understanding the mechanisms of oxynitride barriers in coronary stent modification.

Magnetron Sputter Grown AlN Nanostructures with Giant Piezoelectric Response toward Energy Generation

Piezoelectric III–N semiconductor nanostructures are of increasing interest to be used for sensor technologies and energy harvesting. Within this group of materials, AlN is known for the largest bulk piezoelectric constant, but piezoelectric properties of AlN nanostructures are not well studied. In the current work, AlN nanostructures are fabricated by reactive magnetron sputter deposition at normal and glancing angle orientations on Si substrates covered by a conductive TiN film. Ag nanoparticles are used to facilitate nucleation of the nanostructures, which are found to have a bud-like shape consisting of individual pillars/lamellae. These pillars exhibit a wurtzite-like hexagonal lattice and preferential growth direction along the c-axis. Piezoresponse force microscopy is used to characterize the properties of the nanostructures. Giant values of the piezoresponse coefficient are measured, reaching up to 6 times higher values compared to AlN bulk and thin films. The obtained results create a basis for optimization of the fabrication parameters enabling tuning of the AlN piezoelectric properties and further development of the technology toward the formation of large-area nanoscale matrixes for energy generation.

Reactive pulsed direct current magnetron sputtering deposition of semiconducting yttrium oxide thin film in ultralow oxygen atmosphere: A spectroscopic and structural investigation of growth dynamics

An experimental investigation was conducted to explore spectroscopic and structural characterization of semiconducting yttrium oxide thin film deposited at 623 K (±5K) utilizing reactive pulsed direct current magnetron sputtering. Based on the results obtained from both x-ray diffraction and transmission electron microscope measurements, yttrium monoxide is very likely formed in the transition region between β-Y2O3 and α-Y2O3, and accompanied by the crystalline Y2O3. Resulting from either the low energy separation between 4d and 5s orbitals and/or different spin states of the corresponding orbitals’ sublevels, the stability of monoxide is most presumably self-limited by the size of the crystal in thermodynamic terms. This behavior develops a distortion in the structure of the crystal compared to the metal oxide cubic structure and it also effectuates the arrangement in nanocrystalline/amorphous phase. In addition to this, spectroscopic ellipsometry denotes that the semiconducting yttrium oxide has the dominant, mostly amorphous, formation character over crystalline Y2O3. Our purpose, by means of the current findings, is to advance the understanding of formation kinetics/conditions of yttrium with an unusual valency (2+).

Hard and tough sub-stoichiometric B1 Ta-Mo-Nx films by regulating N content

Ternary transition metal nitrides (TMNs) films with B1 structure (NaCl type) have been widely explored as hard protective materials. Their structure and mechanical performances are influenced by the stoichiometric coefficients (TM: N), while the films with high hardness yet sound toughness could be obtained by regulating the nitrogen content. In this case for the sub-stoichiometric B1 Ta-Mo-Nx films, the microstructure, mechanical properties and the toughening mechanisms by N atoms were investigated. The NaCl-structure sub-stoichiometric Ta0.44Mo0.56Nx films with N concentrations at 0.42 ≤x ≤ 0.73 grown by reactive magnetron sputter deposition. The film with x = 0.59 shows higher hardness (∼36.4 GPa), combined with shorter cracks around indentation and higher scratch resistance, reveals the enhanced fracture toughness (KIC=∼1.67 MPa*m1/2, H/E = 0.14); the film simultaneously obtained a lower wear rate (∼6.6 × 10−7 mm3/N * m) and friction coefficient (∼0.4). The formed point defects in sub-stoichiometric Ta-Mo-Nx films are responsible for the enhanced toughness, while the film with x = 0.59 exhibit an increased p(N) - d-eg(Me) strength character accompanied with high d-t2 g(Me) - d-t2 g(Me) metallic states for the TM-N bonds according to the XPS results.

(Digital Presentation) Reactive Magnetron Sputtering Deposition of La1.6Nd0.4NiO4 Coating As Cathode for Solid Oxide Fuel Cell

Ln2NiO4 (Ln=La, Pr, Nd, etc.) materials with K2NiF4 structures are interesting materials for intermediate temperature solid oxide fuel cell (IT-SOFC) due to Mixed Ionic and Electronic Conductivity (MIEC) [1-2]. The present work is focused on the elaboration of La1.6Nd0.4NiO4 coating obtained by Reaction Magnetron Sputtering (RMS). This compound is a promising oxygen electrode able to decrease the operating temperature of SOFC. After a presentation of the deposition operating conditions for obtaining the films, the structural and microstructural characterizations of the coatings were, respectively, determined by XRD and SEM. The electrical properties were studied as a function of temperature by the 4-probe method. Electrochemical properties were investigated in a symmetrical cell electrode / YSZ / electrode by complex impedance spectroscopy. Finally, a complete cell composed of a commercial anode, and YSZ electrolyte made by RMS and the cathode of this study was tested under hydrogen and air in single SOFC cell configuration.It appeared that the films are amorphous when processed and that they crystallize after an annealing treatment under air. According to this study, a correlation between crystalline structure, morphology and electrical properties will be presented and its last ones are completed by a thermogravimetry analysis.

Effect of processing conditions on residual stress in sputtered transition metal nitrides (TiN, ZrN and TaN): Experiments and modeling

Stress evolution during reactive DC magnetron sputtering deposition in TiN, ZrN and TaN films at different growth rates, pressures and relative gas flow rates was measured by a wafer curvature technique. The results indicate that, for a given growth rate, the stress in each material is tensile at higher pressures and becomes more compressive with lower pressures. At lower pressures, the stress tends to become more compressive with increasing growth rate. Increasing the gas flow rate of N2 relative to Ar is observed to enhance compressive stress generation in TaN but has a weaker effect on TiN and ZrN. At lower pressure, the compressive stress magnitude scales with TiN < ZrN < TaN. The stress at different processing conditions was analyzed in terms of a kinetic model that includes the effects of growth kinetics and energetic bombardment. The resulting parameters are compared with calculations from binary collision Monte-Carlo simulation codes.

Modeling and Experimental Study of Hysteresis during the Reactive Sputter Deposition of Titanium Oxides and Nitrides Using a Pulsed DC Magnetron

There is an ongoing interest in the research and application of thin film coatings containing titanium oxides and titanium nitrides, due to their properties such as photocatalytic activity, mechanical hardness, biocompatibility, and so on. Reactive sputter deposition is widely used for the production of such coatings. A characteristic of this method is the hysteresis, which leads to an ambiguous dependence of the deposition rate and the coating quality on the process conditions. There are a number of theoretical models describing reactive magnetron sputtering. One of the most advanced is the RSD2013 model. Several parameters in this model can only be determined experimentally. This article focuses on the investigation of the hysteresis during the reactive magnetron sputtering deposition process. The RSD2013 parameters that describe the experimental setup were determined, and on their basis the dependences of the characteristics of the hysteresis region on the discharge power, the type of reactive gas, and the working gas pressure were investigated. Additionally, the growth rate of the thin film coating prepared in various modes was compared with the RSD2013 model, which is in agreement with the experimental data. The results obtained from the RSD2013 model in comparison to the experimentally obtained data make it possible to provide an overview of suitable operating modes for the deposition of titanium dioxide and titanium dioxide for the magnetron sputtering device used.

In situ Raman-scattering mapping and resistance study of the VO2 metal-insulator phase transition

In this study, a large-area single-phase VO2 film was successfully prepared on a Si (100) substrate by reactive magnetron sputtering deposition. The thickness of the VO2 film is approximately 220 nm. The phase transition temperature is about 67 °C, with more than three orders of magnitude of the resistance change. X-ray diffraction patterns obtained at different temperatures indicate the coexistence of two phases during the VO2 phase transition process, where a portion of the grains first transform from a monoclinic structure to a rutile structure, and then phase transition expands throughout the film. In situ Raman-scattering mapping scans further prove that the monoclinic-to-rutile phase transition occurs gradually in polycrystalline VO2 films, in which monoclinic and rutile phases coexist from 55 °C to 80 °C. Electrical resistance of the film will change dramatically when the volume fraction of monoclinic phase decreases to 43.5%, or the volume fraction of rutile phase increases to 55.5%. The phase transition temperature differs among the grains in the polycrystalline VO2 film. This study provides an important scientific approach for elucidating the mechanism of the metal-insulator phase transition.

Influence of magnetron sputtering process parameters on low-temperature electrical transport characteristics of zirconium oxynitride thin films

In order to determine the influence of process parameters including nitrogen and oxygen flow rate on the structure and electrical transport characteristics of zirconium oxynitride(ZrOxNy) thin films, the ZrOxNy films were prepared on sapphire substrates by RF reactive magnetron sputtering deposition technology. The crystal orientation and morphology of ZrOxNy films prepared at different nitrogen and oxygen flow rate were characterized by XRD and SEM, respectively. The electric transport behavior of ZrOxNy films at 300K to 3K was measured by PPMS. The results show that the insulativity of ZrN films is enhanced with the increase of nitrogen flow rate in sputtering atmosphere. With the increase of oxygen flow rate in sputtering atmosphere, the insulativity of ZrOxNy film is enhanced.

Direct synthesis of graphene on silicon by reactive magnetron sputtering deposition

In the present research, the graphene was grown directly on the Si (100) substrate by a high-power impulse reactive magnetron sputtering the copper target. The samples' structure, morphology, and composition were investigated by Raman scattering spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy. The synthesis temperature, time, sample position in relation to the magnetron, and grid bias effects were studied. The graphene layer number decreased with growth temperature and distance between the sample and magnetron. The defects density in graphene decreased, and graphene crystallite size increased with synthesis temperature. These parameters were changed with lateral movement of the sample's position. The graphene layer number and defects density non-monotonically depended on the grid bias voltage. We revealed that the synthesis time, the distance between the substrate and the magnetron cathode target surface, and the grid bias voltage determine the graphene surface morphology and the shape and size of the graphene flakes. It was explained by competition between the graphene growth from the CHx species, growth activation by hydrogen, etching by hydrogen and argon ions, radiative defects creation, hydrogen atoms adsorption. The changes of the electrons, argon ions and copper atoms concentration and energy, and methane dissociation products density were taken into account. The temperature gradient and ion bombardment induced stress and their release were considered.

Epitaxial growth of TiN on (0001) semi-insulating 4H-SiC substrate by reactive sputtering

Growth of epitaxial TiN film on a semi-insulating single crystal (0001) SiC substrate has been achieved by DC magnetron reactive sputtering deposition. The effects of growth temperature and N2 flow ratio in Ar on film quality and growth rate were investigated. X-ray diffraction (XRD) characterization shows that all the deposited TiN films at 550 and 700 °C are heteroepitaxially grown on SiC with the epitaxial relationship between TiN and 4H-SiC in (111)TiN//(0001)SiC and [11¯0]TiN//[112¯0]4H-SiC. Increasing the N2 flow ratio from 4 to 8% results in improvement of the film quality and a decrease in the growth rate. The width of the X-ray rocking curve of TiN (111) reflection can reach a value as small as 249 arcsec and the resistivity of TiN film can be 21 μΩ·cm for deposition at 700 °C with 8% N2 flow ratio. Measurements by atomic force microscopy show that the surface roughness of the TiN film can be 1.1 nm. X-ray photoelectron spectroscopy reveals that TiN composition is nearly in stoichiometry for all the grown TiN films. Examinations by cross-sectional transmission electron microscopy show that TiN is directly grown on SiC and verify the epitaxial relationship from XRD.

Structure, properties and applications of diamond-like carbon coatings prepared by reactive magnetron sputtering

AbstractMetal containing and metal free amorphous diamond-like carbon films were prepared by reactive magnetron sputter deposition using targets from transition metals or graphite and acetylene as reactive gas. Both types of coating materials are well known for their low friction coefficients. However, metal containing films exhibit clearly lower wear resistances and lower hardness values than metal free films. To study the differences between both materials, tungsten containing and metal free coatings were compared. The deposition experiments were carried out in an industrial scale d.c. magnetron sputter machine. Transmission electron microscopy, secondary ion mass spectroscopy, and Raman spectroscopy as well as hardness measurements and wear tests were performed to characterize and to compare composition, structure, mechanical, and tribological properties of both coating materials.

Development of titanium nitride thin film microheaters using laser micromachining

In this paper, we report the fabrication and characterization of titanium nitride (TiN) thin-film-based microheaters. TiN thin films have been optimized on Si and SiO2 substrates for their optimum electrical resistivities by controlling the process parameters, including argon:nitrogen (Ar:N2) ratio in reactive pulsed DC magnetron sputter (PDCMS) deposition technique. An optical emission spectroscope (OES) was used for monitoring the plasma characteristics at various nitrogen flow rates. The microstructural and surface properties of the TiN films have been investigated and correlated with the electrical properties. It has been observed that the amount of nitrogen flux in the TiN plasma plays an essential role in the microstructural, surface, and electrical properties of the TiN thin films. Micro-heaters have been fabricated with TiN thin films with low electrical resistivity using laser engraving techniques instead of conventional lithographic and micromachining techniques. The TiN microheater has shown excellent performance. A temperature of 406 °C has been achieved by applying an input power of 8 W. This work paves the path for developing scalable and economic TiN microheaters using laser micromachining techniques.

Effects of atomic oxygen on the growth of NiO films by reactive magnetron sputtering deposition

Reactive sputtering deposition has been widely applied to the preparation of oxide films, but a method is still needed to stably control the deposition process and the film growth. In this work, the plasma in the vicinity of sputtering target is studied by optical emission spectroscopy and the atomic oxygen density ([O]) is linked to the sputtering mode and the growth of NiO films. The NiO films can be deposited either in oxide mode or in the transition region, whereas the [O] value plays an important role in determining the growth behavior of NiO films and the crystallinity. In the transition region, the (111)-oriented growth of NiO films is preferential and the crytallinity is improved with the decrease in the [O] value. In the oxide mode, the NiO films are preferentially (001)-oriented and exhibit a relatively good crystallinity. By fixing the O2/Ar flow ratio at a constant, the [O] value is explored as a function of substrate temperature, showing that the oxygen desorption may have significant impacts on the [O] value as the substrate temperature is higher than 400 °C.

Influence of Impurities on the Front Velocity of Sputter Deposited Al/CuO Thermite Multilayers.

CuO and Al thin films were successively deposited using direct current (reactive) magnetron sputter deposition. A multilayer of five bilayers was deposited on glass, which can be ignited by heating a Ti resistive thin film. The velocity of the reaction front which propagates along the multilayer was optically determined using a high-speed camera. During the deposition of the aluminum layers, air was intentionally leaked into the vacuum chamber to introduce impurities in the film. Depositions at different impurity/metal flux ratios were performed. The front velocity reaches a value of approximately 20 m/s at low flux ratios but drops to approximately 7 m/s at flux ratios between 0.6 and 1. The drop is rather abrupt as the front velocity stays constant above flux ratios larger than 1. This behavior is explained based on the hindrance of the oxygen transport from the oxidizer (CuO) to the fuel (Al).

Compositional gradients at the nanoscale in substoichiometric thin films deposited by magnetron sputtering at oblique angles: A case study on SiOx thin films

AbstractWe demonstrate the existence of stoichiometric variations at the nanoscale when growing nanocolumnar SiOx thin films by reactive magnetron sputtering deposition at oblique angles. Results show stoichiometric variations in the range 0.3 &lt; x &lt; 1.3 when growing a SiO0.5 thin film. This agrees with results from a numerical growth model that obtains a shift of the stoichiometry in all nanocolumns from lower values at the side facing the Si target to higher values at the opposite side. The different momentum distribution of the gaseous reactive and sputtered species results in preferential incorporation of the latter at a particular side of the nanocolumns. The general occurrence of this mechanism during the reactive magnetron sputtering deposition of substoichiometric thin films at oblique angles is discussed.

Highly selective detection of acetone by TiO2-SnO2 heterostructures for environmental biomarkers of diabetes

The n-n TiO2-SnO2 heterostructures composed of SnO2 nanoparticles (NPs) topped with TiO2 NPs have been produced by a novel hybrid reactive magnetron sputtering and pulse laser deposition for sensing acetone (C3H6O) vapors in the environment. The gas sensing characteristics of the TiO2-SnO2 heterostructures were measured over a range of operating temperatures (200–500°C) and the optimal working temperature of 300 °C was fixed. Further, the adsorption of acetone gas on both (110) and (101) stoichiometric and reduced surfaces of TiO2-SnO2 are studied by density functional theory (DFT) calculations. The proposed TiO2-SnO2 sensor displayed an ultrasensitive response for detecting acetone vapors which is almost 12 times and a limit of detection of 0.02 ppm. DFT calculations showed that the adsorption of acetone gas on (110) and (101) facets is thermodynamically favorable. Moreover, TiO2-SnO2 heterostructures sensor displayed high gas response, selectivity, repeatability, and long-term stability. The developed sensor also demonstrated excellent resistance against humidity due to a good synergy between the component oxides, band bending, availability of chemisorbed oxygen, and adsorption-desorption mechanism at the TiO2-SnO2 heterojunction. This work provides a foundation for the development of advanced gas sensors for hazardous sensing of materials exposed to diabetic patients in the human environment.

The Investigation of Microstructure, Photocatalysis and Corrosion Resistance of C-Doped Ti–O Films Fabricated by Reactive Magnetron Sputtering Deposition with CO2 Gas

By employing carbon dioxide as one source of reaction gases, carbon-doped Ti–O films were fabricated via reactive magnetron sputtering deposition. The chemical bonding configurations and microstructure of the films were analyzed by Raman spectrum and SEM, respectively. The effect of pH on the photocatalytic activities of the films was determined via evaluation of the decolorization rate of methyl orange under alkali, acid and neutrality conditions using UV light irradiation. Electrochemical impedance spectroscopy and potentiodynamic polarization tests were employed to determine the anti-corrosion properties. Compared with the C-free Ti–O film, the C-doped Ti–O films exhibit superior corrosion resistance. Furthermore, the results of the photodegradation experiment suggest that the C-doped Ti–O films have excellent photocatalytic activities and, for methyl orange, those with higher carbon content exhibit hyper-photodegradative effect under the alkali condition.