Reactive Magnetron Sputtering Technique Research Articles

Thermal activation and temperature dependent PL and CL of Tb doped amorphous AlN and SiN thin films

AbstractThe effect of terbium (Tb) doping on the photoluminescence (PL) and cathodoluminescence (CL) spectra of amorphous aluminum nitride (a ‐AlN) and amorphous silicon nitride (a ‐SiN) thin films has been investigated for different temperature conditions. The samples were prepared by RF dual magnetron reactive sputtering technique with a Tb concentration of about ∼1 at% An enhancement of the light emission is obtained after thermal annealing treatments following the activation of luminescent centers. Furthermore, the Tb related integrated light emission intensity is reported exhibiting a continuous increase with the samples temperature well below thermal quenching for both materials. This behavior suggests a phonon assisted energy migration mechanism which contributes to the effective energy transfer from the matrix to the Tb ions. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Evaluation of a Metal Supported Ni-YSZ / YSZ / La2NiO4 IT-SOFC Elaborated by Physical Surface Deposition Processes

The elaboration of the last generation of metal supported IT-SOFCs by physical surface deposition processes is really challenging. Atmospheric Plasma Spraying (APS) process appears to be well adapted to build the porous anode layer [1] whereas Reactive Magnetron Sputtering (RMS) technique is suitable to deposit thin and dense layer. In the present work, we have deposited a Ni-YSZ anode by APS on porous metallic supports (ITM) produced by PLANSEE SE. Then, a thin YSZ electrolyte film was applied by RMS. Details about the elaboration of the half cell could be found in a previous work [2]. Various strategies have been followed to deposit the cathode layer on top of the previously deposited anode and electrolyte coatings. The Mixed Ionic and Electronic Conductor K2NiF4 structured material presents interesting electrocatalytic properties [3] allowing its utilization as cathode layer. Recent studies deal with the use of thin layers as cathodes in IT-SOFCs [4]. Therefore, RMS process was also evaluated to deposit a thin La2NiO4 layer (LNO) according to already optimized operating conditions [5]. In order to compare the efficiency of this dense layer as an individual cathode or a bonding cathode layer, the complete IT-SOFC building was elaborated by replacing and/or adding a screen-printed La2NiO4 coating (SP LNO). This layer was developed and optimized in ICMCB laboratory and has shown interesting performances in LNO/GDC/LNO half cells [6]. GDC diffusion barrier layers were deposited by RMS in order to limit the deleterious interaction between active layers in use. Different cells with RMS LNO, SP LNO, and RMS LNO + SP LNO were produced and tested in a complete cell bench at 973 K. Impedance Spectroscopy and Voltametry measurements were performed on these samples to assess their electrochemical characteristics and performances. The electrochemical resistances of these cells are too high and their performances are still lower than the literature ones. Analyses of the samples after the electrochemical tests permit to identify the density of the RMS LNO layer as the limiting factor lowering the cathodic electrochemical reaction. The sintering step performed on complete cells with SP LNO deteriorates the layers deposited by RMS as well as the metallic support explaining these performances. Nevertheless, using LNO bonding layer manufactured by RMS seems to be an interesting way to improve the polarization resistance of the cell.

Photoanodes with Fully Controllable Texture: The Enhanced Water Splitting Efficiency of Thin Hematite Films Exhibiting Solely (110) Crystal Orientation.

Hematite, α-Fe2O3, is considered as one of the most promising materials for sustainable hydrogen production via photoelectrochemical water splitting with a theoretical solar-to-hydrogen efficiency of 17%. However, the poor electrical conductivity of hematite is a substantial limitation reducing its efficiency in real experimental conditions. Despite of computing models suggesting that the electrical conductivity is extremely anisotropic, revealing up to 4 orders of magnitude higher electron transport with conduction along the (110) hematite crystal plane, synthetic approaches allowing the sole growth in that direction have not been reported yet. Here, we present a strategy for controlling the crystal orientation of very thin hematite films by adjusting energy of ion flux during advanced pulsed reactive magnetron sputtering technique. The texture and effect of the deposition mode on the film properties were monitored by XRD, conversion electron Mössbauer spectroscopy, XPS, SEM, AFM, PEC water splitting, IPCE, transient photocurrent measurements, and Mott-Schottky analysis. The precise control of the synthetic conditions allowed to fabricate hematite photoanodes exhibiting fully textured structures along (110) and (104) crystal planes with huge differences in photocurrents of 0.65 and 0.02 mA cm(-2) (both at 1.55 V versus RHE), respectively. The photocurrent registered for fully textured (110) film is among record values reported for thin planar films. Moreover, the developed fine-tuning of crystal orientation having a huge impact on the photoefficiency would induce further improvement of thin hematite films mainly if cation doping will be combined with the controllable texture.

Cu/TiO2 thin films prepared by reactive RF magnetron sputtering

Cu/TiO2 thin films were deposited on glass substrates by reactive RF magnetron sputtering technique. Crystalline structure, surface morphology and electronic structure were studied using X-ray diffraction (XRD), field emission scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy (XPS). Transmittance and absorptance of these films were characterized by UV–Vis spectroscopy. XRD patterns demonstrate that TiO2 films deposited on glass substrate at 300 °C are observed to be in pure anatase phase, whereas Cu/TiO2 films are amorphous in nature at 300 °C substrate temperature. The crystallinity of Cu/TiO2 thin films decreases with increasing the dopant concentrations of Cu in TiO2 films. XPS studies show that Cu is in +2 oxidation state in all films. The optical band gap of Cu/TiO2 films decreases from ~3.3 to ~2.0 eV with the increase in the copper concentration. Further, antimicrobial studies of Cu/TiO2 films with ~3.9 at.% Cu exhibit high transmittance and best antimicrobial activity against E. coli and S. aureus compared to other doped films.

Flexible electrochromics: magnetron sputtered tungsten oxide (WO3−x) thin films on Lexan (optically transparent polycarbonate) substrates

Tungsten oxide (WO3−x) based electrochromics on flexible substrates is a topic of recent interest. The present communication reports the electrochromic properties of WO3−x thin films grown on lexan, an optically transparent polycarbonate thermoplastic substrate. The WO3−x films are prepared at room temperature (300 K) by the reactive DC magnetron sputtering technique. The physical properties of metal oxide thin films are known to be controlled by the oxygen stoichiometry of the film. In the present work, the WO3−x thin films are prepared by varying the oxygen flow rates. All the WO3−x thin films are amorphous in nature. The electrochromic performance of the WO3−x thin films is evaluated by cyclic voltammetry measurements on tin doped indium oxide (ITO) coated lexan and glass substrates. The optical band gap of WO3−x thin films grown on lexan substrates (at any given oxygen flow rate) is significantly higher than those grown on glass substrates. The coloration efficiency of WO3−x thin films (at an oxygen flow rate of 10 sccm) on lexan substrates is: 143.9 cm2 C−1 which is higher compared to that grown on glass: 90.4 cm2 C−1.

Optical and electrical properties of thermochromic VO2 thin films on Pt layers

VO2 thin films have been successfully deposited on Pt(111)/Ti/SiO2/Si substrate by means of reactive magnetron sputtering technique. The IR reflectance of the as-prepared films exhibited a big contrast (∼50%) between the room temperature (25°C) and high temperature (100°C) owing to the fancy semiconductor-metal transition of VO2 thin film. Nevertheless, the initial resistance was very low and the transition cannot be triggered by the electrical field. Authors believe that the rather poor electrical switching behaviour was connected to the leakage current from the large grain boundaries and pores in the surface of the VO2 thin film. This study may provide insights for VO2 films grown on Pt(111)/Ti/SiO2/Si substrates and suggest that Pt layers can serve as a suitable substrate of VO2 films for optical switching devices but not for electrical switching ones.

Tribological study of TiN monolayer and TiN/CrN (multilayer and superlattice) on Co–Cr alloy

The wear performance of the Co–Cr alloys used for total joint replacement is a critical variable for the success of the implant. In order to add information in this field, the effect of superlattice coatings on wear response was investigated. In this work, TiN/CrN superlattices produced alternating TiN and CrN layers of nanometer-scale, were deposited by the means of reactive magnetron sputtering technique using two types of disc substrates: cast Co–Cr (ASTM F75) and cast Co–Cr+1wt% B alloys. As the first attempt, a simple ball-on-disc tribological configuration was performed using Ringer׳s solution and Al2O3 balls. In addition, scratch testing, optical and scanning electron microscopy were used to elucidate on the wear mechanisms involved. Adhesive and abrasive wear mechanisms were found on the wear track. Co–Cr+1wt% B showed massive secondary phases precipitation which increases the adherence resistance in the interface between the system coating and the substrate improving slightly the wear response.

Thermal annealing effects on ultra-violet luminescence properties of Gd doped AlN

We studied energy transfer from AlN to doped Gd3+ ions as a function of the post-thermal annealing temperature. Gd-doped AlN thin films were deposited on fused-silica substrates using a reactive radio-frequency magnetron sputtering technique. The film is a c-axis oriented polycrystal. The intra-orbital electron transition in Gd3+ showed an atomically sharp luminescence at 3.9 eV (318 nm). The photoluminescence (PL) excitation spectrum exhibited a resonant peak, indicating efficient energy transfer from the host AlN crystal to Gd3+ ions. The PL intensity increases approximately ten times by thermal annealing. The PL decay lifetime becomes long with annealing, and mid-gap luminescence relating to the crystal defects in AlN was also found to be reduced by annealing. These results suggest that energy dissipation of excited carriers in AlN was suppressed by annealing, and the efficiency of energy transfer into Gd3+ was improved.

Preparation and characterization of dye-sensitized TiO2 nanorod solar cells

TiO2 nanorods were prepared by DC reactive magnetron sputtering technique and applied to dye-sensitized solar cells (DSSCs). The length of the TiO2 nanorods was varied from 1μm to 6μm. The scanning electron microscopy images show that the nanorods are perpendicular to the substrate. Both the X-ray diffraction patterns and Raman scattering results show that the nanorods have an anatase phase; no other phase has been observed. (101) and the (220) diffraction peaks have been observed for the TiO2 nanorods. The (101) diffraction peak intensity remained constant despite the increase of nanorod length, while the intensity of the (220) diffraction peak increased almost linearly with the nanorod length. These nanorods were used as the working electrodes in DSSCs and the effect of the nanorod length on the conversion efficiency has been studied. An optimum photoelectric conversion efficiency of 4.8% has been achieved for 4μm length nanorods.

Cd-composition induced effects on structure, optical and electrical properties of sputtered Zn1−xCdxO films

Zn1−xCdxO films with different Cd contents (0≤x≤1) were successfully deposited on quartz substrates by the direct current reactive magnetron sputtering and post-annealing techniques. It was found that structures, band gaps and electrical properties of the films can be tuned by changing Cd contents x. The Zn1−xCdxO film consists of wurtzite phase with highly (002)-preferred orientation at x from 0 to 0.2, mixture of wurtzite and cubic phases at x=0.5, and cubic phase with highly (200)-preferred orientation at x≥0.8. The band gap decreases from 3.25eV at x=0 to 2.75eV at x=0.2 for the wurtzite Zn1−xCdxO, and decreases from 2.52eV at x=0.8 to 2.42eV at x=1, which has a little change for cubic Zn1−xCdxO. In addition, Hall measurement results indicate that the influence of Cd content on the conduction behavior of Zn1−xCdxO films is significant. The chemical compositions and the bonding states of Zn1−xCdxO films were examined by X-ray photoelectron spectroscopy analysis.

The spectral selective absorbing characteristics and thermal stability of SS/TiAlN/TiAlSiN/Si3N4 tandem absorber prepared by magnetron sputtering

Spectrally selective TiAlN/TiAlSiN/Si3N4 multilayer coatings were deposited on stainless steel (SS) plate using a reactive direct current magnetron sputtering technique. In this tandem absorber system, TiAlN, TiAlSiN and Si3N4 act as the main absorbing layer, the semi-absorbing layer and the antireflection layer, respectively. An average absorptance (α) of 0.938 and emittance (ε) of 0.099 were achieved in coatings prepared under optimized conditions, which exhibit a fine-grained morphology and an amorphous microstructure as evidenced by SEM and XRD analysis, respectively. Absorptance and emittance data, as well as Raman spectra were collected for coatings exposed to different levels of thermal stresses (2h in air @200°C, 300°C, 400°C, 500°C, 600°C). These heat treated coatings showed negligible to small degradations in their selective absorbing capabilities as compared with the as-grown ones. There was no significant change of the coatings in their morphology or composition after the heat treatments, as evidenced by the SEM and Raman spectra analysis, respectively. The spectral selectivity of the coatings remained stable after a heat-treatment at 272°C in air for 300h.

Effects of nitrogen composition on the resistivity of reactively sputtered TaN thin films

Nanocrystalline tantalum nitride (TaN) thin films have been deposited by reactive direct current magnetron sputtering technique on Si/SiO2 (100) substrate with nitrogen flow rate ranging from 0, 3, 5, 7, 9 to 11 standard cubic centimeter per minute (sccm). Structural properties, surface morphology, chemical composition and and resistivity of the TaN films were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy, X-ray photoemission spectroscopy (XPS) and four-point probe measurements, respectively. In the XRD spectra, a classical formation sequence of tantalum nitride phases in the order of Ta-Ta2N-TaN-Ta4N5 and decreasing amount of metallic Ta were observed with increasing nitrogen flow. The electrical resistivity of the TaN film was found to increase with increasing N/Ta ratio as a result of the increased electron scattering from interstitial N atoms. In the XPS analysis, two groups of Ta4f doublets relating to different TaN phases were observed in the core level spectra of TaN films. No strong coupling was observed between the Ta4f doublets and the Ta4p and the N1s groups. The appropriate nitrogen flow was believed to be helpful in the bonding and formation of stoichiometric TaN. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of thermal annealing on structural, optical and electrical properties of RF reactive magnetron sputtered CdO thin films

Recently, there has been a lot of interest on transparent conducting oxide (TCO) materials which have common application in solar cells and some optoelectronic devices. In this work, cadmium oxide (CdO) thin films have been deposited on glass substrates by RF reactive magnetron sputtering technique and subsequently annealed in air from 200 °C to 500 °C. The effect of annealing temperature on the structural, morphological, optical and electrical properties of CdO films is systematically investigated by X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, UV-visible spectrophotometer and Hall effect measurements. X-ray diffraction (XRD) studies showed that the films are polycrystalline in nature with a preferential orientation along (2 0 0) plane. Atomic force microscopy studies showed that these films are very smooth with maximum root mean square roughness of 3.13 nm. The CdO films formed at annealing temperature of 400 °C exhibited optical transmittance of 84%, electrical resistivity of 1.9 × 10 −3 Ω cm and figure of merit of 1.8 × 10 −3 Ω −1 .

Effects of Si content on microstructure and mechanical properties of TiAlN/Si3N4-Cu nanocomposite coatings

TiAlN/Si3N4-Cu nanocomposite coatings of various Si content (0–5.09at.%) were deposited on AISI-304 stainless steel by DC reactive magnetron sputtering technique. The chemical composition, microstructure, mechanical and tribological properties of these coatings were systematically investigated by means of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), nanoindentation tester, a home-made indentation system, a scratch tester and a wear tester. Results indicated that with increasing Si content in these coatings, a reduction of grain size and surface roughness, a transformation of the (111) preferred orientation was detected by XRD and FESEM. Furthermore the hardness of these coatings increase from 9.672GPa to 18.628GPa, and the elastic modulus reveal the rising trend that increase from 224.654GPa to 251.933GPa. However, the elastic modulus of TiAlN/Si3N4-Cu coating containing 3.39at.% Si content dropped rapidly and changed to about 180.775GPa. The H3/E2 ratio is proportional to the film resistance to plastic deformation. The H3/E2 ratio of the TiAlN/Si3N4-Cu coating containing 3.39at.% Si content possess of the maximum of 0.11GPa, and the indentation test indicate that few and fine cracks were observed from its indentation morphologies. The growth pattern of cracks is mainly bending growing. The present results show that the best toughness is obtained for TiAlN/Si3N4-Cu nanocomposite coating containing 3.39at.% Si content. In addition, the TiAlN/Si3N4-Cu coating containing 3.39at.% Si content also has good adhesion property and superior wear resistance, and the wear mechanism is mainly adhesion wear.

On the dependence of structural and sensing properties of sputtered MoO3 thin films on argon gas flow

Nitrogen and carbon oxides (CO, NO and NO2), released from combustion facilities and automobiles, are known to be extremely harmful to the human body and also are the main cause of air pollution. Therefore, effective methods to monitor and suppress the carbon and nitrogen oxides have been highly demanded for atmospheric environmental measurements and controls. It is known that molybdenum oxide (MoO3) can be a good semiconductor material for use as a gas sensor in monitoring CO, NO and NO2. In this paper we report the structural characteristics and sensing properties of the sputtered MoO3 thin films as a function of argon gas flow. MoO3 thin films were deposited by DC reactive magnetron sputtering technique on glass substrates at different argon gas flows in the range of 5–20sccm. X-ray diffraction (XRD) analysis was used for studying crystallographic structure. XRD results showed that all of our films were of polycrystalline structure and of α-MoO3 stable orthorhombic phase. Results also showed that crystallite size increases while compressive nano-strain in the structure of the films decreases with increasing the argon gas flow. Atomic force microscope and the field emission scanning electron microscope studies showed granular structures for all samples, which increased in size consistent with the XRD results, with argon gas flow, while the surface roughness of the films also increased with argon gas flow. Chemical composition study showed optimum reaction between oxygen and molybdenum atoms for films produced at 15sccm flow of argon gas. The electrical response of samples was measured in the vacuum and the CO environments in the temperature range of 150–350K. All samples showed Ohmic behavior and the electrical resistances of the films measured in the CO environment were lower than those measured in vacuum. This study showed that the sensing ability of MoO3 for CO improves with increasing the argon gas flow.

Growth of the [110] Oriented TiO2 Nanorods on ITO Substrates by Sputtering Technique for Dye-Sensitized Solar Cells

TiO2 films have been deposited on ITO substrates by dc reactive magnetron sputtering technique. It has been found that the sputtering pressure is a very important parameter for the structure of the deposited TiO2 films. When the pressure is lower than 1 Pa, the deposited film has a dense structure and shows a preferred orientation along the [101] direction. However, the nanorod structure has been obtained as the sputtering pressure is higher than 1 Pa. These nanorods structure TiO2 film shows a preferred orientation along the [110] direction. The phases of the deposited TiO2 films have been characterized by the x-ray diffraction and the Raman scattering measurements. All the films show an anatase phase and no other phase has been observed. The results of the SEM show that these TiO2 nanorods are perpendicular to the ITO substrate. The TEM measurement shows that the nanorods have a very rough surface. The dye-sensitized solar cells (DSSCs) have been assembled using these TiO2 nanorod films prepared at different sputtering pressures as photoelectrode. And the effect of the sputtering pressure on the properties of the photoelectric conversion of the DSSCs has been studied.

Effect of bias voltage on compositional, mechanical and corrosion property of ZrNbAlN multilayer films by unbalanced magnetron sputtering

Nano-scaled ZrNbAlN films with different negative bias voltages (Vb) were deposited on bronze substrate and Si (100) wafers by a reactive unbalanced magnetron sputtering technique. Composition and structure properties were characterized by X-ray photoelectron spectroscopy and X-ray diffraction. It is found that mole concentrations of Zr and Nb are affected by Vb, which leads to the increase of binding energy of N 1s and Al 2p and decrease of binding energy of Zr 3d5/2 and Nb 3d5/2. Surface morphologies evolution controlled by Vb could be observed. Furthermore, X-ray diffraction patterns reveal that these films show a (111) preferred orientation. Moreover, mechanical property and corrosion behavior of ZrNbAlN films were characterized by nanoindentation test and corrosion test, respectively. A maximum value of 21.85 GPa at −70 V occurs in the ZrNbAlN- bronze system, which outperforms uncoated bronze. Corrosion experiments in 0.5 mol/L NaCl and 0.5 mol/L HCl solution show that corrosion potential and corrosion current are dependent on Vb, and better anti-corrosion property could be obtained at −90 V.

Effect of substrate temperature on structural, optical and electrical properties of sputtered NiO-Ag nanocrystalline thin films

NiO-Ag thin films were deposited on Corning 7059 glass substrates by DC reactive magnetron sputtering technique and investigated the substrate temperature (T s ) dependent properties of NiO-Ag thin films. X-ray diffraction results showed that crystalline films can be obtained at high T s and all films have a preferred crystal growth texture with face centered cubic (f cc ) structure and was also confirmed by Raman studies. The grain size, transmittance, band gap, mobility and carrier concentrations were increased with T s . Room temperature deposited films have an average roughness around 6.9 nm where as increment of T s resulted in increased roughness up to 14 nm with nanocrystalline morphology. The optimum substrate temperature to obtain NiO-Ag films was found to be 200°C. It was found that with increasing the T s , resistivity of the films was significantly decreased.

Preparation and characterization of Nickel Oxide thin films by direct current reactive magnetron sputtering at different substrate temperatures

The influence of substrate temperature on the properties NiO films, prepared by dc reactive magnetron sputtering technique, is studied by various characterization methods. X-ray diffraction studies revealed that the crystal structure is highly influenced by the substrate temperature. The optical results indicated that the optical transmittance and band gap of the films increased with the increase of substrate temperature up to 523 K. The optical band gap of NiO films decreases from 3.82 to 3.70 eV with the increase of substrate temperature from 523 to 723 K. The electrical resistivity decreased with the increase of substrate temperature from 303 to 723 K, whereas carrier concentration and Hall mobility increased with increasing the substrate temperature.

Fabrication and Physical Properties of Thin Films TiNx for Infrared Absorption

Infrared absorptivity of pixel arrays plays a pivotal role in bolometer performance. There are a series reports focusing on improving the absorptivity in last two decades [1, 2]. Many materials have been examined as suitable infrared light absorbers, such as thin films MoSix and TiNx. In general, the optimized sheet resistance is ~ 377Ω/square related to the absorption [3-4]. However, there are fewer reports on the investigation of synergetic effects from ultrathin substrate SiNx, which is a desirable material during microfabrication process of the bolometers. In this paper, we present the experimental and optical analysis for construction of the film TiNx on SiNxsubstrates. The thin films TiNx were prepared by reactive magnetron sputtering technique under Ar/N2 atmosphere. The RF sputtering power is 350 W and the total gas flux is about 25 sccm. The amount (N2%) of nitrogen as a function of Ohm-square at the temperature (25, 200 oC) are summarized in fig 1. It shows that the sheet resistance is sensitive to the substrates temperature. The logarithmic value of sheet resistance is approximately proportional to N2 ratio at the substrate temperature from 25 oC to 200 oC. The reaction rate is rather slow at low temperature (25 oC) even with a high reactant gas concentration for TiNx growth. The relatively high substrate temperature (200 oC) is desirable for the TiNx growth. The resistivity with 13% N2 at 200 oC is close to the value 377Ω/square in literature [3-4]. The light absorptivity of multilayer structure (TiNx/SiNx/Al, SiNx/Al) has been recorded by Fourier Transform Infrared Spectroscopy, as shown in Fig. 2. It can be seen that the infrared absorptivity of the sandwich-type structure (TiNx/SiNx/Al) shows higher IR absorption than that of the structure SiNx/Al. The structure TiNx/SiNx/Al shows obviously enhanced resonant peak in 1/4 of 3/4 wavelength optical thickness due to the existence of Fabry-Perot resonator, which related to the Peak A and C of the recorded spectra. The intrinsic absorption of SiNx can be indexed to Peak B and D. As compared with the pristine SiNx, it can be seen that the absorption dramatically increases at the wavelength 8 um (peak C). In summary, we report preparation of thin film TiNx through reactive magnetron sputtering technique. The optimized resistivity of the films is applied to build a resonant structure for enhancing infrared absorptivity. A drastically increases has been obtained as compared with the pristine SiNx.