Influence of process parameters on structure and optical properties of GeC thin films deposited by RF magnetron sputtering

Germanium carbide (Ge_1 − xC_x) films on silicon and quartz substrates have been prepared by the radio frequency (RF) reactive sputtering of a pure Ge target in a CH₄/Ar discharge. Their structural and optical properties have been investigated as functions of the substrate temperature (T_S) and the CH₄ percentage to the gas mixture. The optical band gap of the films lies within the range 0.96-1.65 eV, varying proportionally with the carbon content and in inverse proportionality with T_S.     

Photocatalytic activity of reactively sputtered and directly sputtered titania coatings

It is well known that, depending on deposition conditions, the structure of titania coatings may be amorphous, anatase or rutile, or a mixture of phases, and that the anatase phase is the most promising photocatalyst for the degradation of organic pollutants. The formation of anatase depends on the energy delivered to the growing film, which in turn depends on the operating parameters chosen. In this study, titania coatings have been deposited onto glass substrates by pulsed magnetron sputtering both from metallic targets in reactive mode and directly from oxide powder targets. The as-deposited coatings were analysed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and micro-Raman spectroscopy. Selected coatings were then annealed at temperatures in the range of 400–700 °C and re-analysed. The photocatalytic activity of the coatings has been investigated through measurements of the degradation of organic dyes, such as methyl orange, under the influence of UV and fluorescent light sources. Further sets of coatings have been produced both from metallic and powder targets in which the titania is doped with tungsten. These coatings have also been analysed and the influence of the dopant element on photocatalytic activity has been investigated. It has been found that, after annealing, both sputtering processes produced photo-active surfaces and that activity increased with increasing tungsten content over the range tested. Furthermore, the activity of these coatings under exposure to fluorescent lamps was some 50–60% of that observed under exposure to UV lamps.     

Characterizations of CrN/a-CNx nanolayered coatings deposited by DC reactive magnetron sputtering of Cr and graphite targets

CrN/a-CN_x nanolayered coatings have been deposited by DC reactive magnetron sputtering of pure Cr and graphite targets. The total thickness is 1 μm and that of a-CN_x layers is kept constant at 3.5 nm. The period (bilayer thickness) is in the range 8-16 nm. CrN and a-CN_x layers are crystalline and amorphous respectively. The decrease of CrN layers’ thickness (decrease of period) in the stack leads to refinement of CrN microstructure associated with (200) preferred orientation. The hardness of nanolayered films is independent of the period’s thickness, while internal compressive stress, which remains between that of each elementary layer, follows an evolution close to that of the law of mixtures. The best tribological behaviours are reached for a periods’ thickness of 8 nm.     

Preferentially oriented vanadium nitride films deposited by magnetron sputtering

Because of solid state lubricious properties of vanadium oxides, wear resistant coatings based on nitrides and carbides of that metal are still of interest for research teams. The aim of this report is to show phase composition evolution from metallic vanadium through intermediate phases up to δ-VN phase supersaturated with nitrogen in thin films deposited by reactive, pulsed magnetron sputtering from vanadium target. This analysis is completed by remarks on preferential orientation, lattice constant and crystallite size. Presented work is a part of research on composite hard coatings for woodworking tools where vanadium nitrides and carbides are considered as a component reducing friction.     

Stress evolution in magnetron sputtered Ti-Zr-N and Ti-Ta-N films studied by in situ wafer curvature: Role of energetic particles

Stress evolution during reactive magnetron sputtering of binary TiN, ZrN and TaN thin films as well as ternary Ti-Zr-N and Ti-Ta-N solid-solutions was studied using real-time wafer curvature measurements. The energy of the incoming particles (sputtered atoms, backscattered Ar, ions) was tuned by changing either the metal target (M_Ti = 47.9, M_Zr = 91.2 and M_Ta = 180.9 g/mol), the plasma conditions (effect of pressure, substrate bias or magnetron configuration) for a given target or by combining different metal targets during co-sputtering. Experimental results were discussed using the average energy of the incoming species, as calculated using Monte-Carlo simulations (SRIM code). In the early stage of growth, a rapid evolution to compressive stress states is noticed for all films. A reversal towards tensile stress is observed with increasing thickness at low energetic deposition conditions, revealing the presence of stress gradients. The tensile stress is ascribed to the development of a ‘zone T’ columnar growth with intercolumnar voids and rough surface. At higher energetic deposition conditions, the atomic peening mechanism is predominant: the stress remains largely compressive and dense films with more globular microstructure and smooth surface are obtained.     

Thickness dependent properties of nickel oxide thin films deposited by dc reactive magnetron sputtering

Nickel oxide thin films of various thicknesses were grown on glass substrates by dc reactive magnetron sputtering technique in a pure oxygen atmosphere with sputtering power of 150 W and substrate temperature of 523 K. Crystalline properties of NiO films as a function of film thickness were investigated using X-ray diffraction. XRD analysis revealed that (200) is the preferred orientation and the orientation of the films changed from (200) to (220) at film thickness of 350 nm. The maximum optical transmittance of 60% and band gap of 3.82 eV was observed at the film thickness of 350 nm. The lowest electrical resistivity of 5.1 Ω cm was observed at a film thickness of 350 nm, thereafter resistivity increases with film thickness.     

Power and pressure effects upon magnetron sputtered aluminum doped ZnO films properties

In this work, polycrystalline aluminum doped zinc oxide (ZnO:Al) films with c-axis (002) orientation have been grown on glass and silicon substrates by RF (radio frequency) magnetron sputtering technique, at room temperature. A systematic study of the effect of sputtering deposition parameters (i.e. RF power and argon gas pressure) on the structural, optical and electrical properties of the films was carried out. We observed that, with increasing RF power the growth rate increased, while it decreased with increasing gas pressure. As mentioned above, the films were polycrystalline in nature with a strong preferred (002) orientation. The intrinsic compressive stress was found to decrease with both increasing RF power and gas pressure, and near stress-free film was obtained at 200 W RF power and 2 × 10^− 1 Pa gas pressure. The obtained ZnO:Al films, not only have an average transmittance greater than 90% in the visible region, but also have an optical band gap between 3.33 and 3.47 eV depending on the sputtering parameters. Moreover, a low value of the electrical resistivity (~ 1.25 × 10^− 3 Ω cm) was obtained for the film deposited at 200 W and 2 × 10^− 3 mbar.     

Tribological properties of Ti2N-Wx% coatings deposited by magnetron sputtering

Ti₂N-W_x% coatings with different tungsten contents were deposited using unbalanced magnetron sputtering technology. The microstructures and mechanical properties of Ti₂N-W_x% coatings have been characterized by SEM, X-ray diffraction (XRD), nanoindentation and adhesion techniques. The tribological performance of the coatings was investigated using an oscillating friction and wear tester under dry conditions. Indexable inserts with Ti₂N-W_x% coatings were applied to turning AISI 1045 steel material by a lathe. Micron-drills with Ti₂N-W_x% coatings were adopted in the ultra-high speed (10⁵ rpm) Printed Circuit Board (PCB) through-hole drilling test. Experimental results indicate that the coating microstructure, mechanical properties and wear resistance vary according to the tungsten content. Ti₂N-W_14% coated inserts showed the best wear resistance in 1045 steel turning and PCB through-hole drilling tests. The service life of a Ti₂N-W_14% coated tool is five times greater than that of an uncoated tool in PCB through-hole drilling test.     

Property variations of direct-current reactive magnetron sputtered copper oxide thin films deposited at different oxygen partial pressures

Cuprous oxide (Cu₂O) and cupric oxide (CuO) thin films were deposited on glass substrates at different oxygen partial pressures by direct-current reactive magnetron sputtering of pure copper target in a mixture of argon and oxygen gases. Oxygen partial pressure was found to be a crucial parameter in controlling the phases and, thus, the physical properties of the deposited copper oxide thin films. Single-phase Cu₂O thin films with cubic structure were obtained at low oxygen partial pressure between 0.147 Pa and 0.200 Pa while higher oxygen partial pressure promoted the formation of CuO thin films with base-centered monoclinic structure. Polycrystalline Cu₂O thin films deposited with oxygen partial pressure at 0.147 Pa possessed the lowest p-type resistivity of 1.76 Ω cm as well as an optical band gap of 2.01 eV. On the other hand, polycrystalline CuO thin films deposited with oxygen partial pressure at 0.320 Pa were also single phase but showed a n-type resistivity of 0.19 Ω cm along with an optical band gap of 1.58 eV.     

Magnetron sputtering of TiOxNy films

This article reports on the characterization and preparation of N-doped titanium dioxide (TiO₂) films by reactive magnetron sputtering from Ti(99.5) targets in a mixture of Ar/O₂/N₂ atmosphere on unheated glass substrates. A dual magnetron system supplied by a dc bipolar pulsed power source was used to sputter the TiO_xN_y films. The amount of N in the TiO_xN_y film ranges from 5 to 40 at%. Its structure was measured using X-ray diffraction (XRD), the optical band gap was calculated from Tauc plots and the decrease of the water contact angle α_ir after the film activation by UV irradiation was investigated as a function of at% of N in the TiO_xN_y film. The yellow-coloured TiO_xN_y films with high (≈8 at%) amount of N exhibited a strong decrease of the band gap E_g down to 2.7 eV. A significant decrease of the water contact angle α_ir after UV irradiation has been observed for 2 μm thick transparent nanocrystalline (anatase+rutile) N-doped TiO₂ films containing less than 6 at% of N.     

Influence of the target composition on reactively sputtered titanium oxide films

Titanium dioxide thin films have many interesting properties and are used in various applications. High refractive index of titania makes it attractive for the glass coating industry, where it is used in low-emissivity and antireflective coatings. Magnetron sputtering is the most common deposition technique for large area coatings and a high deposition rate is therefore of obvious interest. It has been shown previously that high rate can be achieved using substoichiometric targets. This work deals with reactive magnetron sputtering of titanium oxide films from TiO_x targets with different oxygen contents.The deposition rate and hysteresis behaviour are disclosed. Films were prepared at various oxygen flows and all films were deposited onto glass and silicon substrates with no external heating. The elemental compositions and structures of deposited films were evaluated by means of X-ray photoelectron spectroscopy, elastic recoil detection analysis and X-ray diffraction. All deposited films were X-ray amorphous. No significant effect of the target composition on the optical properties of coatings was observed. However, the residual atmosphere is shown to contribute to the oxidation of growing films.     

Optical and chemical characterization of thin TiNx films deposited by DC-magnetron sputtering

Thin titanium nitride (TiN_x) films were deposited on silicon substrates by means of a reactive DC-magnetron plasma. Layers were synthesized under various conditions of discharge power and nitrogen flows in two operation modes of the magnetron (the so-called “balanced” and “unbalanced” modes). The optical constants of the TiN_x films were investigated by spectroscopic ellipsometry (SE). X-ray photoelectron spectroscopy (XPS) was used to determine the relative atomic concentration and chemical states of the TiN_x films. The density and thickness of the films have been investigated by means of grazing incidence X-ray reflectometry (GIXR). The results of the layer analyses were combined with plasma investigations carried out by means of energy resolved mass spectrometry (ERMS) under the same conditions. It is shown that the magnetron mode has a clear influence on the titanium deposition rate and the incorporation of nitrogen into the layers.     

Relationship between chemical compositions of magnetron sputtered B-C-N films and various experimental parameters

By adjusting a series of experimental parameters, amorphous B-C-N films with various compositions were synthesized on silicon (100) substrate via radio frequency magnetron sputtering. The bonding characteristics and chemical compositions of B-C-N films were characterized by FTIR and XPS. On the B-C-N ternary phase diagram, the chemical compositions of most synthesized films distribute near the C-BN isoelectronic line. Among them, the low-carbon compositions can be obtained by decreasing the N₂/Ar flow ratio, increasing the power of boron and graphite targets simultaneously, or increasing the substrate temperature; those carbon-rich ones can be prepared by introducing the CH₄ gas into the mixture of N₂/Ar reactive gas. Therefore, it is possible to control the compositions of B-C-N films by adjusting a set of experimental parameters.     

XPS analysis of WxCy thin films prepared by sputter deposition

W_xC_y thin films with different compositions were studied in order to correlate their properties with the thin-film composition and chemical bonding of C and W atoms. Three W_xC_y thin films with C concentrations in the range 40-80 at% were deposited on WC-Co substrates by the plasma beam sputtering technique. The composition of the thin films and chemical states of elements were analysed by X-ray photoelectron spectroscopy (XPS) depth profiling. The C and W concentrations in the films were quantified using XPS intensities from a WC-Co substrate with a known composition. The C1s peaks in the high energy resolution XPS spectra of thin films allowed identification of the WC phase and the amorphous carbon phase as a function of the film composition. The results show that the amorphous carbon a-C phase is present in those films with composition x<y. The measured hardness of the films decreases with a decrease of the WC concentration.     

Morphological study of magnetron sputtered Ti thin films on silicon substrate

Titanium films on Si(1 0 0) substrate were deposited by DC-magnetron sputtering. The effect of substrate temperature on the microstructural morphologies of the films was characterized by using field emission-based scanning electron microscopy/electron back scattered difffraction (FE-SEM/EBSD) and atomic force microscopy (AFM). X-ray diffraction was used to characterize the phases and crystallite size of the Ti films and it was observed that according to the first figure of this article: (0 0 2) orientation increases from 200 °C and it changes into (1 0 1) orientation from 300 °C. The SEM analysis of the Ti films, deposited in Ar atmosphere, showed two- and three-dimensional hexagonal structure of the grains at the substrate temperature of 200 °C and >200 °C, respectively. The increase in grain size of Ti films with the substrate temperature was confirmed by EBSD and AFM characterization. The average surface roughness of the Ti films has increased with increase in substrate temperature as evident from the AFM study.     

Optical, electrical and mechanical properties of the tantalum oxynitride thin films deposited by pulsing reactive gas sputtering

Thin films of tantalum oxynitride were prepared by reactive magnetron sputtering using a Ta target and N₂ and O₂ as reactive gases. The nitrogen flow was kept constant while the oxygen flow was pulsed periodically. The film composition evolves progressively from TaO_0.25N_1.51 to TaO_2.42N_0.25 while increasing the oxygen pulse duty cycle without any abrupt change in the elemental content. The optical transmission spectra of the films deposited on glass show a “blue shift” of the absorption edge with increasing oxygen content. X-ray diffraction (XRD) patterns of all films exhibit broad peaks typical for nanocrystalline materials. Cross-section film morphology is rather featureless and surface topography is smooth exhibiting very small grains, in agreement with the results obtained by XRD. The optical properties of the films are very sensitive to their chemical composition. All films exhibit semiconducting behaviour with an optical band gap changing from 1.85 to 4.0 eV with increasing oxygen content. In order to evaluate the potential of the tantalum oxynitride films for microelectronic applications some Ta-O-N films were integrated in a MOS structure. The results of the capacitance-voltage measurements of the system Al//Ta-O-N//p-Si are discussed with respect to the chemical composition of the Ta-O-N films.     

Influence of nitrogen flow rate on the physical properties of ZrOxN1−x coatings produced by magnetron sputtering

In this work we produce ZrO_xN_1−x thin coatings and ZrYO_xN_1−x by DC reactive magnetron sputtering. In order to study the effect of nitrogen flow rates on physical and mechanical properties, the N₂/O₂ relation was changed between 0.025 and 0.2. The addition of nitrogen to the ZrO₂ and ZrO₂Y₂O₃ systems was performed to study the influence on the stabilization of the high temperature tetragonal or cubic phases of ZrO₂. X-ray diffraction (XRD) measurements were used to characterize the coating structures and to study the influence of nitrogen addition on the high temperature stabilized phases. The residual stresses were also determined by measuring the radius of curvature of the thin-coated substrates. The surface microtopography was analyzed by Atomic Force Microscopy (AFM) and the roughness was evaluated. Energy Dispersive X-ray (EDX) Spectroscopy was used to assess the thin film composition. Scanning Electron Microscopy (SEM) was used to measure the film thickness, to observe microstructure of the film cross-section and to analyze the surface morphology.     

Preparation of B-C-N films by magnetron sputtering with different N2/Ar flow ratio

Amorphous B-C-N films were fabricated on silicon (100) substrates using radio frequency reactive magnetron sputtering technique with variable N₂/Ar flow ratios. The structures, chemical bonding and mechanical properties were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. We found that the N concentration is insensitive to the increment of N₂/Ar flow ratio while the B concentration decreases and C concentration increases. All B-C, C-N, and B-N bond contents increase as the N₂/Ar flow ratio varies from 1/10 to 5/10. Further improving the N₂/Ar flow ratio will promote N atoms prior to bonding with C, resulting in decreased B-C and increased C-N bond content, respectively. The changes of bond content lead to a shift of the main peaks of B1s, C1s, and N1s spectra toward higher binding energies. The hardness of B-C-N thin films is almost invariant with the N₂/Ar flow ratio.     

Effect of deposition angle on the structure and properties of pulsed-DC magnetron sputtered TiAlN thin films

This article reports the comparison of structure and properties of titanium aluminum nitride (TiAlN) films deposited onto Si(100) substrates under normal and oblique angle depositions using pulsed-DC magnetron sputtering. The substrate temperature was set at room temperature, 400 °C and 650 °C, and the bias was kept at 0, − 25, − 50, and − 80 V for both deposition angles. The surface and cross-section of the films were observed by scanning electron microscopy. It was found that as the deposition temperature increases, films deposited under normal incidence exhibit distinct faceted crystallites, whereas oblique angle deposited (OAD) films develop a kind of “tiles of a roof” or “stepwise structure”, with no facetted crystallites. The OAD films showed an inclined columnar structure, with columns tilting in the direction of the incident flux. As the substrate temperature was increased, the tilting of columns nearly approached the substrate normal. Both hardness and Young's modulus decreases when the flux angle was changed from α = 0° to 45° as measured by nanoindentation. This was attributed to the voids formed due to the shadowing effect. The crystallographic properties of these coatings were studied by θ-2θ scan and pole figure X-ray diffraction. Films deposited at α = 0° showed a mixed (111) and (200) out-of-plane orientation with random in-plane alignment. On the other hand, films deposited at α = 45° revealed an inclined texture with (111) orientation moving towards the incident flux direction and the (200) orientation approaching the substrate normal, showing substantial in-plane alignment.     

Bias effect on microstructure and mechanical properties of magnetron sputtered nanocrystalline titanium carbide thin films

Nanocrystalline titanium carbide (TiC) thin films were prepared by magnetron sputtering deposition at 473 K. The effect of substrate bias on microstructure and mechanical properties was studied in details using X-ray photoelectron spectroscopy, X-ray diffraction, field emission scanning electron microscopy, indentation and scanning microscratch. The TiC films exhibit a (111) preferential orientation. Substrate bias decreases grain size and deposition rate of the TiC films. The TiC films have columnar structure which becomes finer at high substrate bias. Nanoindentation hardness, Young's modulus, and toughness of the films are increased as the substrate bias goes up. However, the adhesion peaks at substrate bias of − 100 V and drops when bias is increased further.