Non-reactive Sputtering Research Articles

On the Evaluation of Corrosion Resistances of Amorphous Chromium-Carbon Thin-Films

The possibility of evaluating the corrosion resistance of amorphous chromium carbide (Cr-C) films containing nanometre-sized carbide grains embedded in an amorphous carbon matrix on the basis of polarization curves, voltammograms and the oxidation charge have been studied for Cr-C films with different carbon concentrations. The films, which were manufactured by non-reactive direct-current magnetron sputtering, were studied in 1.0 mM H2SO4 at both 22°C and 80°C, and with scanning electron microscopy and X-ray photoelectron spectroscopy prior to and after the electrochemical experiments. It is demonstrated that the oxidation of these Cr-C films gives rise to a surface composed of Cr2O3 and partially oxidized carbon and that the non-corroding oxidation current due to carbon oxidation increases with increasing carbon concentration in the films as well as with the electrolyte temperature. Since the oxidation current is composed of contributions from both Cr–C and carbon oxidation it is not straightforward to evaluate the corrosion resistances of these films based on the current in the passive region, the mixed potential (i.e., the corrosion potential) or the open circuit potential. The present results in fact indicate that Cr-C films with high carbon concentrations may have better corrosion resistances than the corresponding films with lower carbon concentrations although larger currents in the passive region can be seen in polarization curves.

Growth of co-sputtered titanium-strontium films: influence of strontium concentration and ion bombardment

Strontium-containing titanium films were synthesized by non-reactive magnetron sputtering from elemental targets. Three series of depositions were carried out at (1) different relative Sr-to-Ti target powers, (2) different sputter-gas pressures, and (3) different bias voltages. Large amounts of oxygen were detected in films with high Sr concentrations as well as in films exhibiting a porous morphology. By the addition of Sr, amorphous regions appeared in the coatings with a corresponding reduction of the crystalline volume fraction. The amorphous phase fraction increased with increasing Sr content. Upon increasing the Sr contents to 7.2at.% and higher, completely X-ray amorphous coatings were obtained. However, from high-resolution transmission electron microscopy imaging of the film containing 7.2at.% Sr, Ti nanocrystals of the order ~6nm embedded in an amorphous matrix were observed. Furthermore, the absolute value of the floating potential increased with decreasing sputter-gas pressure, resulting in a more energetic ion bombardment of the growing films. Strong resputtering of strontium resulted in very low Sr concentrations in films deposited at floating potential and low gas pressures or with an applied bias voltage. Films deposited at floating potential and high gas pressures exhibited a porous columnar morphology and had low degrees of crystallinity with correspondingly small grain sizes (~9nm), whereas denser and more crystalline films with larger grains (~18nm) were obtained from depositions at floating potential and low gas pressures and from depositions with an applied bias voltage. Film hardness scaled linearly with film electron density, as evidenced from nanoindentation and X-ray reflectivity measurements.

AlCuFe(Cr) and AlCoFeCr coatings for improvement of elevated temperature oxidation resistance of a near-α titanium alloy

In this work, an AlCuFe, AlCuFeCr and AlCoFeCr multicomponent coatings were deposited on a near-α titanium alloy, TIMETAL 834, by a non-reactive magnetron sputtering. A microstructure, phase composition, coatings adhesion to the substrate, micro-mechanical properties and oxidation resistance were investigated. The AlCuFe coating was quasicrystalline and consisted of icosahedral ψ-Al65Cu20Fe15 phase grains. The AlCuFeCr coating consisted mainly of decagonal d-AlCuFeCr phase and some Al6.1Cu1.2Ti2.7 phase grains. The AlCoFeCr coating microstructure was composed of AlCrFe2 nanocrystals embedded in an Al13Co4 matrix.It was established that all multicomponent coatings exhibit higher hardness and elastic moduli than the titanium alloy substrate. Among all investigated coatings, the AlCoFeCr one exhibits the best adhesion to the substrate. It was found that a very brittle, non-protective scale formed on the uncoated alloy during isothermal oxidation consisted of TiO2 (rutile) grains. The oxidation resistance of the TIMETAL 834 alloy at elevated temperature (750°C) was significantly improved by the coatings deposition. The smallest weight gain during oxidation test, 82% lower than in the case of uncoated sample, was found for the AlCoFeCr coated alloy. The microstructure investigation of the specimen after oxidation test was performed by SEM and TEM. It was found that the improvement of oxidation resistance of TIMETAL 834 by the coatings deposited in the present work is mainly due to an occurrence of the protective α-Al2O3 scale.

Microstructure, chemical states, and mechanical properties of V–C–Co coatings prepared by non-reactive magnetron sputtering

V–C–Co coatings have been prepared by non-reactive magnetron co-sputtering from VC and Co targets. The microstructure, chemical states, and mechanical properties are examined as a function of Co content in the coatings. The coatings are dense, with columnar growth structures. High resolution transmission electron microscopy (HRTEM) studies identify a nanocomposite microstructure for the 12.4at.% Co coating, in which ligament-like Co-rich regions partially separate the nanocrystalline VC grains. X-ray photoelectron spectroscopy studies reveal a noticeable charge transfer from Co 2p states to C 1s states. This charge transfer, in addition to the ligament-like Co-rich regions as revealed by HRTEM, points to the formation of a strong Co/VC interface. The nanoindentation hardness of the coatings drops steadily with the Co content, from 29GPa for pure VC to ~21GPa for the 12.4at.% Co coating. Meanwhile, the plasticity characteristic increased from 0.42 to 0.53.

Photoconductivity and transient response of Al:ZnO:Al planar structures fabricated via a thermal oxidation process

We have investigated the photoconductivity and transient response of polycrystalline ZnO films grown using a thermal oxidation technique. Zinc-metal films were grown on c-plane sapphire substrates via non-reactive dc sputter deposition at room temperature with subsequent thermal annealing at 300°C, 600°C, 900°C, and 1200°C. Metal–semiconductor–metal Al:ZnO:Al planar ultraviolet (UV) photodetectors were fabricated via sputter deposition of aluminum contacts. Decreasing photoconductivity is seen for increasing annealing temperature, which is consistent with photoluminescence studies showing a similar decrease in the green-to-UV emission ratio. As-grown photodetectors annealed at low temperature (300°C) over 9h demonstrated a responsivity of ~100mA/W. We also present a phenomenological model of photoconductivity transients in which transient recoveries are fitted with a linear combination of two exponential decays. Although annealing temperature did have a significant effect on photocurrent saturation, there was no such relationship for post-illumination recovery time constants.

Fabrication of Porous Noble Metal Thin-Film Electrode by Reactive Magnetron Sputtering

Porous platinum films have been fabricated by reactive sputtering combined with subsequent thermal annealing. Using the SEM, XRD, XPS, and polarization resistance measurement techniques, the microstructural development of the film and its resultant electrochemical properties have been characterized. Pore evolution was understood as a result of the thermal grooving of platinum during annealing process. We demonstrated that crystallization should be followed by agglomeration for the evolution of porous microstructures. Furthermore, reaction sputtering affected the adhesion enhancement between the film and substrate compared to the film deposited by non-reactive sputtering. The polarization resistance of the porous platinum film was five times lower than that of the dense platinum film. At 600 degrees C the resistance of the porous film was 5.67 omega x cm2, and that of the dense film was 38 omega x cm2.

Influence of Ti addition on the structure and properties of low-friction W–S–C coatings

Transition metal dichalcogenides, such as WS2 and MoS2, are known for their layered structure and lubricating properties. When deposited as thin coatings, however, their use as solid lubricants is limited by their low hardness and load-bearing capacity. The addition of another element, such as carbon, can improve the mechanical properties, although the hardness of for example W–S–C coatings is still rather low. In this work, Ti has been added to W–S–C coatings in order to further increase the hardness by carbide formation. W–S–C and W–S–C–Ti coatings were deposited by non-reactive magnetron sputtering, and characterized with regard to composition, structure and mechanical and tribological properties. It was found that the addition of Ti leads to the formation of a new carbide phase, and a significant increase in hardness for coatings with moderate carbon contents. The friction properties of W–S–C–Ti coatings were found to be comparable to that of W–S–C coatings, with friction coefficients down to μ≈0.02 and similar wear rates against steel in a dry atmosphere. Formation of WS2 in the wear track of W–S–C–Ti was confirmed by transmission electron microscopy. It has thus been shown that the addition of Ti to W–S–C coatings can increase the hardness, while still maintaining WS2 lubrication.

Substrate heating and post-annealing effect on tungsten/tungsten carbide bilayers grown by non-reactive DC magnetron sputtering

Abstract Tungsten–tungsten carbide (W/WC) bilayers were produced by non-reactive DC magnetron sputtering at various substrate temperatures between room temperature and 300 °C. The coatings were characterized in terms of morphology, structure and chemical composition using several techniques such as X-ray diffraction (XRD), Raman Spectroscopy, Auger Electron Spectroscopy (AES), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Scanning Probe Microscopy (SPM) in the Atomic Force Microscopy (AFM) mode. Bragg peaks corresponding to the (110) diffraction plane of the W phase and (111), (200), (220) and (311) peaks corresponding to the cubic WC phase were identified. From the XRD analysis, a strong influence of the substrate temperature on the grain size and crystallographic texture was observed; nevertheless, a poor influence on the lattice parameter and microstrain was detected. Furthermore, different vibrational modes of the W3C structure and characteristic peaks corresponding to O3W3O bonds were observed. Depth profile analysis was also carried out using AES, which revealed the presence of C, W, O and Fe. Initially, carbon and tungsten were observed in the WC layers. After the films were totally etched, Fe from the substrate was detected. However, the morphology was not significantly affected by temperature. An important result was the improvement in the coatings' adherence when an interlayer of W was inserted. In this work, the bilayers' behavior during annealing was also studied. The films were observed to oxidize at approximately 600 °C.

Exploring the benefits of depositing hard TiN thin films by non-reactive magnetron sputtering

The aim of this paper is to compare the mechanical and tribological properties of TiN coatings prepared in a conventional magnetron sputtering chamber according to two different routes: the usual reactive sputtering of a Ti target in an Ar/N2 atmosphere vs. the comparatively more simple sputtering of a TiN target in a pure Ar atmosphere. Improved properties in term of hardness and wear rates were obtained for films prepared by non-reactive sputtering route, due to the lower presence of oxynitride species and larger crystalline domain size. Additionally, a significant hardness enhancement (up to 45GPa) is obtained when a −100V d.c. bias is applied during growth. This behaviour is explained by non-columnar growth and small grain size induced by effective ion bombarding. These results demonstrate that non-reactive sputtering of TiN target appears a simple and efficient method to prepare hard wear-resistant TiN films.

Study of CrNx and NbC interlayers for HFCVD diamond deposition onto WC–Co substrates

Chromium nitride (CrNx) and niobium carbide (NbC) films were deposited by magnetron sputtering on Co-cemented tungsten carbide (WC–Co) substrates and diamond deposition was performed by using hot-filament chemical vapor deposition (HFCVD) technique. The CrNx and NbC interlayers have been deposited at different substrate temperatures (TS=400, 550 and 700°C). The stability of these interlayers for diamond deposition has been studied by a heat treatment in H2 atmosphere for 60h at a temperature of 765°C in the HFCVD reactor. X-ray diffraction (XRD), scanning electron microscopy (SEM) and glow discharge optical emission spectroscopy (GDOES) confirmed that due to this heat treatment the CrNx films transformed into porous films composed of CrNx, Cr3C2, Cr7C3 and Co phases, accompanied by a dramatic loss of nitrogen which is replaced by carbon. It was observed that higher nitrogen contents in the CrNx films reduce the Co diffusion through the CrNx layer. For NbC films, deposited by non-reactive magnetron sputtering from an NbC compound target, the heat treatment in the HFCVD reactor revealed that the films are absolutely stable during the heat treatment with some relaxation of residual stresses up to a factor of about 3. Furthermore it was found that Co diffuses through the NbC films with a TS-dependant accumulation on the NbC film surface. By HFCVD it was possible to deposit adherent diamond coatings on the CrNx and NbC interlayers. However, a reasonable adhesion of diamond on NbC was only obtained after different pre-treatments of the WC–Co substrates. The adhesion seems to be mainly governed by the topography of the WC–Co substrates.

Effects of the Argon Pressure on the Optical Band Gap of Zinc Oxide Thin Films Grown by Nonreactive RF Sputtering

Zinc oxide (ZnO) thin films were grown by nonreactive RF sputtering at room temperature under varying argon pressures (PAr). Their optical band gap was found to increase from 3.58 to 4.34 eV when the argon pressure increases from 2.67 to 10.66 Pa. After annealing at 200°C and 500°C, optical band gaps decrease considerably. The observed widening of the band gap with increasingPArcan be understood as being a consequence of the poorer crystallinity of films grown at higher pressures. Measurements of morphological and electrical properties of these films correlate well with this picture. Our main aim is to understand the effects ofPAron several physical properties of the films, and most importantly on its optical band gap.

Structure, composition, and physicomechanical characteristics of HfB2 and Hf-B-N films

The paper deals with the study of the effect of the deposition conditions (the bias potential and substrate temperature) on the structure, composition, and physicomechanical characteristics of nanocrystalline films of hafnium diboride and boridonitride formed by the method of nonreactive (in Ar) and reactive (in Ar + N2) HF magnetron sputtering, respectively. The optimal conditions for the deposition of the hafnium diboride coatings with growth texture in plane (00.1) and the best physicomechanical characteristics are deter-mined. It is shown that at a bias potential of ±50 V and a substrate temperature of ∼500°C superstoichiometric highly textured films are formed with a nanohardness of 44 GPa and an elastic modulus of 396 ± 11 GPa. A relation between the composition, structure, and physicomechanical characteristics of the films is found. Reactive sputtering in (Ar + N2) makes it possible to produce amorphous-crystalline films of the composite (HfB2 + BN) that consists of grains of the HfB2 nanocrystalline phase, the spaces between which are filled with the amorphous phase of graphite-like BN.

Influence of Sputtering Power on the Structure and Photoelectric Property of Ga Doped ZnO Films

Ga-doped ZnO (GZO) films were prepared on glass substrates at 523K temperature by non-reactive DC magnetron sputtering. The effects of sputtering power on microstructure and properties of the GZO films were investigated by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), Hall effect measurements and UV-Vis-NIR spectrometer. The results show that GZO thin films exhibit high c-axis-orientation, and the intensity of peak increase as the enhanced of sputtering power; the increase of power will reduce the film’s visible-light transmittance, but for all of the GZO thin films the average transmittance of the visible-light is above 80%. The sheet resistance of GZO films decreases when the sputtering power gradually heightened from 80W to 200W. The lowest resistivity of 6.559×10-4Ω•cm can be obtained in the condition of the sputtering power is 100W, and the lowest square resistance is 7.9Ω/□.

Transparent conductive ZnO:B films deposited by magnetron sputtering

This paper focuses on the preparation of boron doped ZnO (ZnO:B) films prepared by nonreactive mid-frequency magnetron sputtering from ceramic target with 2wt.% doping source. Adjusting power density, ZnO:B film with low resistivity (1.54×10−3Ωcm) and high transparency (average transparency from 400 to 1100nm over 85%) was obtained. Different deposition conditions were introduced as substrate fixed in the target center and hydrogen mediation. Hall mobility increased from 11 to above 26cm2/V·s, while carrier concentration maintained almost the same, leading to low resistivity of 6.45×10−4Ωcm. Transmission spectra of ZnO:B films grown at various growth conditions were determined using a UV–visible-NIR spectrophotometer. An obvious blue-shift of absorption edge was obtained while transmittances between 600nm and 1100nm remained almost the same. Optical band baps extracted from transmission spectra showed irregular enhancement due to the Burstein–Moss effect and band gap renormalization. Photoluminescence spectra also showed a gradual increase at UV emission peak due to free exciton transition near band gap. We contributed this enhancement in both optical band gap and UV photoluminescence emission to the lattice structure quality melioration.

Synthesis and characterization of photochromic Ag-embedded TiO2 nanocomposite thin films by non-reactive RF-magnetron sputter deposition

Ag-embedded TiO2 nanocomposite thin film with reversible photochromic properties were prepared by layer-by-layer non-reactive RF-magnetron sputtering. Films were produced in Ar/O2 and pure Ar atmospheres. In the oxidizing regime, a diffusion of Ag from the film volume to the outer film surface was observed. Therefore, pure Ar plasma was applied in the deposition of TiO2. The electronic and optical properties of the TiO2 film were almost not affected by the presence of oxygen. Transmission electron microscopy (TEM) and reflection mode X-ray absorption spectroscopy (XAS) were performed to study the morphology, crystal structure and chemical state of the embedded Ag nanoparticles before and after the annealing step. Annealing of the film led to the crystallization of the TiO2 matrix. Moreover, the Ag nanoparticles in the film underwent Ostwald ripening leading to particle agglomerate. No oxidation of the embedded Ag during the sputter deposition and subsequent annealing process was found as confirmed by XAS measurements. The non-reactive RF-magnetron method is believed to avoid the energetic oxygen ions attack to Ag during the deposition of Ag-embedded TiO2 nanocomposite and thus the films are expected to have better optical properties and long-term stability.

Deposition and characterization of magnetron sputtered amorphous Cr–C films

Thin films in the Cr–C system with carbon content of 25–85 at.% have been deposited using non-reactive DC magnetron sputtering from elemental targets. Analyses with X-ray diffraction and transmission electron microscopy confirm that the films are completely amorphous. Also, annealing experiment show that the films had not crystallized at 500 °C. Furthermore, X-ray spectroscopy and Raman spectroscopy show that the films consist of two phases, an amorphous CrCx phase and an amorphous carbon (a-C) phase. The presence of two amorphous phases is also supported by the electrochemical analysis, which shows that oxidation of both chromium and carbon contributes to the total current in the passive region. The relative amounts of these amorphous phases influence the film properties. Typically, lower carbon content with less a-C phase leads to harder films with higher Young’s modulus and lower resistivity. The results also show that both films have lower currents in the passive region compared to the uncoated 316L steel substrate. Finally, our results were compared with literature data from both reactively and non-reactively sputtered chromium carbide films. The comparison reveals that non-reactive sputtering tend to favour the formation of amorphous films and also influence e.g. the sp2/sp3 ratio of the a-C phase.

Microstructure development and properties of the AlCuFe quasicrystalline coating on near-α titanium alloy

A protective quasicrystalline AlFeCu coating was deposited on TIMETAL 834 substrate by nonreactive magnetron sputtering in order to improve resistance of the alloy to oxidation. Microstructure characterisation of the substrate and the coating was performed by analytical scanning- and transmission electron microscopy as well as X-ray diffractometry. Depending on annealing temperature and time, the deposited coating (2.7μm thick) has a different microstructure. The coating in Specimen 1 (annealed 600°C/4h in vacuum) consisted of two zones: outer, composed of Al5Fe2 and Al2Cu3 phases and inner, in which only quasicrystalline ψ phase was present. The coating in Specimen 2 (annealed 600°C/4h+700°C/2h in vacuum) was fully quasicrystalline and consisted of icosahedral ψ phase.Both coatings exhibit higher microhardness than the substrate material. It was established that the applied surface treatment essentially improves oxidation resistance of the alloy tested at 750°C during 250h in static air. Sample weight gain was 60% lower than in the case of uncoated sample. Oxide scale spallation occurred for uncoated alloy while the coated one did not show any spallation. It was found that the very brittle scale formed during oxidation on the uncoated alloy was consisting of TiO2, while that on the coated one consisted mainly of α-Al2O3.

Structural and temperature-related disordering studies of Cu 6PS 5I amorphous thin films

Cu 6PS 5I thin films were deposited onto silicate glass substrates by non-reactive radio frequency magnetron sputtering. Spectrometric and isoabsorption studies of Cu 6PS 5I thin films in the temperature interval 77–500 K were performed. Structural studies were carried out using X-ray diffraction and scanning electron microscopy techniques. Temperature evolution of optical transmission spectra as well as temperature dependences of optical pseudogap and Urbach energy is investigated. The influence of temperature-related and structural disordering on the Urbach tail is studied.

Laser microstructuring and annealing processes for lithium manganese oxide cathodes

It is expected that cathodes for lithium-ion batteries (LIB) composed out of nano-composite materials lead to an increase in power density of the LIB due to large electrochemically active surface areas but cathodes made of lithium manganese oxides (Li–Mn–O) suffer from structural instabilities due to their sensitivity to the average manganese oxidation state. Therefore, thin films in the Li–Mn–O system were synthesized by non-reactive radiofrequency magnetron sputtering of a spinel lithium manganese oxide target. For the enhancement of the power density and cycle stability, large area direct laser patterning using UV-laser radiation with a wavelength of 248nm was performed. Subsequent laser annealing processes were investigated in a second step in order to set up a spinel-like phase using 940nm laser radiation at a temperature of 680°C. The interaction processes between UV-laser radiation and the material was investigated using laser ablation inductively coupled plasma mass spectroscopy. The changes in phase, structure and grain shape of the thin films due to the annealing process were recorded using Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The structured cathodes were cycled using standard electrolyte and a metallic lithium anode. Different surface structures were investigated and a significant increase in cycling stability was found. Surface chemistry of an as-deposited as well as an electrochemically cycled thin film was investigated via X-ray photoelectron spectroscopy.

In-situ analysis of positive and negative energetic ions generated during Sn-doped In 2O 3 deposition by reactive sputtering

Using a quadrupole mass spectrometer combined with an energy analyser, we have investigated the in-situ energy distribution of highly energetic ions generated during reactive sputtering of In–Sn alloy (IT) targets and non-reactive sputtering of Sn-doped In 2O 3 (ITO) ceramic targets. Ar +, In +, O +, O −, O 2 −, InO − and InO 2 − ions with kinetic energies greater than 40 eV were clearly observed. Upon increasing the O 2 flow ratio for reactive sputtering, the surface of the IT target changes from metal (metal mode) to oxide (oxide mode) via a state of mixed metal and oxide (transition region). O − ions with the kinetic energy corresponding to cathode voltage are generated at the oxide layer, which expands upon the target surface with increasing O 2 flow ratio in the metal mode and the transition region. In contrast, the flux of 60-eV Ar + ions decreases with increasing O 2 flow ratio. The presence of 125- and 200-eV In + ions is attributed to the dissociation of InSnO 2 − and InO 2 − with the kinetic energy corresponding to cathode voltage, respectively, while the presence of 40- and 150-eV O + ions is attributed to the dissociation of InO 2 − and O 2 − with the kinetic energy corresponding to cathode voltage, respectively.