Sputter Deposition Conditions Research Articles

Microstructures, electrical and mechanical properties of the magnetron sputter deposited metal thin films at variable angles

In this work, we investigate the microstructures, mechanical and electrical properties of the Cr, Fe, Ni, Cu, and Al thin films that were grown by using magnetron sputtering at various angles. The relationships among the electrical and mechanical properties (resistivity, nanoindentation hardness, and modulus), structural parameters (domain size, thickness, column angle), and sputter deposition conditions (flux angle, deposition rate) were investigated through the Pearson correlation analysis. Electrical resistivity was found to be significantly affected by both the domain size and the deposition rate. A strong correlation between hardness and domain size was observed. However, Young's moduli did not exhibit a correlation within the investigated parameter space.

Exploring the relationship between sputter-deposition conditions and electrochemical response of ZrO2 films on biodegradable MgZnCa alloy

In this work, we investigated the enhancement of corrosion resistance in a biodegradable Mg-0.7Zn-0.6Ca (wt. %) alloy (MgZnCa) by applying ZrO2 thin films deposited via reactive magnetron sputtering. We employed a fractional factorial experimental design to systematically examine the influence of the deposition power, deposition time, and O2 fraction on the effectiveness of the ZrO2 thin film in preventing corrosion of the Mg alloy. Our analysis revealed that the ZrO2 thin films exhibited a monoclinic crystal phase and maintained stoichiometry across various O2 fractions. Interestingly, we observed a 78% roughness reduction when using the lowest O2 fraction, while roughness increased with the deposition power and time. The corrosion response of bare and ZrO2-coated MgZnCa alloy was assessed by electrochemical techniques and detection of H2 production during the Mg corrosion via gas chromatography. The optimal set of deposition conditions, essential for enhancing the short-term corrosion resistance of magnetron-sputtered ZrO2 coatings, involves maximizing thickness through high power (400 W) and extended deposition time (90 min). It is crucial to balance these factors while maintaining an appropriate O2 fraction (20%) to ensure the formation of a stoichiometric film. Avoiding excess oxygen is imperative, as it can lead to undesirable intergranular porosity and surface roughness. This optimization resulted in a 46% reduction in the evolution of H2 gas compared to the bare MgZnCa alloy. Overall, this work sheds light on the potential of ZrO2 thin films as effective corrosion-resistant coatings for MgZnCa alloys, emphasizing the critical role of deposition parameters in achieving superior protection against corrosion.

Optimizing Sputter Deposition Conditions of Silver Thin Films Used in Low-Emissivity Coatings in an In-Line Deposition System

This research sought to determine the optimal conditions for depositing thin silver layers in the fabrication of low-emissivity coatings. The study utilized an in-line semi-industrial high-vacuum magnetron sputtering system with rectangular targets, closely resembling those used in industrial settings. Trilayer AZO/Ag/AZO structures were deposited to enhance the wetting properties of the silver, and to protect it from the atmosphere. The effects of the power and argon flow on the sample properties were analyzed, along with variations in the silver thickness. The results demonstrate that a lower power (200 W) and higher argon flows (1000 sccm) lead to a higher transmittance and a lower sheet resistance, resulting in a reduced emissivity (up to 0.015 for 24 nm of silver). The identified optimal conditions offer valuable recommendations for producing more efficient and optically superior coatings. This study also reveals the importance of the silver thickness to the properties of the coatings, in accordance with previous research findings. These findings provide insights for improving the performance of low-emissivity coatings in various applications.

Correlation between plasma characteristics, morphology, and microstructure of sputtered CuAl alloy films with varied target geometry

The effect of target geometry on coating microstructure and morphology is correlated to changes in deposition conditions, plasma characteristics, and film growth during planar and hollow cathode sputtering. The sputtering plasma properties for the two target geometries were characterized via Langmuir probe analysis as a function of power density and Ar pressure to determine the evolution of ion density for each configuration. Films were then synthesized at the low (0.4 W cm−2) and high (1.2 W cm−2) power densities and characterized using x-ray diffraction, scanning electron microscopy, and electron backscatter diffraction to link changes in texturing, morphology, and microstructure with variations in ion density and sputtering deposition conditions caused by target geometry. It was observed that varying target geometry led to an over threefold increase in deposition rate, homologous temperature, and ion density, which altered the morphology and texture of the film without significant changes to the grain size.

263 nm wavelength UV-C LED on face-to-face annealed sputter-deposited AlN with low screw- and mixed-type dislocation densities

Regarding deep-ultraviolet optical device applications, face-to-face annealed sputter-deposited AlN (FFA Sp-AlN) is a promising alternative to the conventional metalorganic vapor phase epitaxy (MOVPE)-prepared AlN templates on sapphire substrates. However, FFA Sp-AlN tends to exhibit AlGaN growth-related hillock generation and surface morphology deterioration. In this study, we optimized the sputter-deposition conditions for AlN and MOVPE growth conditions for AlGaN to respectively reduce hillock density and size. After confirming AlGaN surface-flattening, we fabricated 263 nm wavelength UV-C LEDs on the FFA Sp-AlN and achieved maximum external quantum efficiencies of approximately 4.9% and 8.0% without and with silicone encapsulation, respectively.

Effect of Magnetron Sputtering Deposition Conditions on the Mechanical and Tribological Properties of Wear-Resistant Titanium Carbonitride Coatings

In the present work, the titanium carbonitride coatings were deposited by the reactive magnetron sputtering method at different substrate bias: 0, −70 V, and −100 V. The effect of the substrate bias on the structure, composition, and mechanical and tribological properties of titanium carbonitride coatings was studied. Scanning electron microscopy, nanoindentation, sliding wear test (ball-on-disk method), X-ray phase, and elemental analysis methods were used to evaluate the tribological properties and microstructure of the thin coatings. The dependencies obtained resulted in the determination of the most preferred mode of deposition by magnetron sputtering at a negative substrate bias in an atmosphere of argon–acetylene–nitrogen.

Optical Characterization of H-Free a-Si Layers Grown by rf-Magnetron Sputtering by Inverse Synthesis Using Matlab: Tauc–Lorentz–Urbach Parameterization

Several, nearly-1-µm-thick, pure, unhydrogenated amorphous-silicon (a-Si) thin layers were grown at high rates by non-equilibrium rf-magnetron Ar-plasma sputtering (RFMS) onto room-temperature low-cost glass substrates. A new approach is employed for the optical characterization of the thin-layer samples, which is based on some new formulae for the normal-incidence transmission of such a samples and on the adoption of the inverse-synthesis method, by using a devised Matlab GUI environment. The so-far existing limiting value of the thickness-non-uniformity parameter, Δd, when optically characterizing wedge-shaped layers, has been suppressed with the introduction of the appropriate corrections in the expression of transmittance. The optical responses of the H-free RFMS-a-Si thin films investigated, were successfully parameterized using a single, Kramers–Krönig (KK)-consistent, Tauc–Lorentz oscillator model, with the inclusion in the model of the Urbach tail (TLUC), in the present case of non-hydrogenated a-Si films. We have also employed the Wemple–DiDomenico (WDD) single-oscillator model to calculate the two WDD dispersion parameters, dispersion energy, Ed, and oscillator energy, Eso. The amorphous-to-crystalline mass-density ratio in the expression for Ed suggested by Wemple and DiDomenico is the key factor in understanding the refractive index behavior of the a-Si layers under study. The value of the porosity for the specific rf-magnetron sputtering deposition conditions employed in this work, with an Ar-pressure of ~4.4 Pa, is found to be approximately 21%. Additionally, it must be concluded that the adopted TLUC parameterization is highly accurate for the evaluation of the UV/visible/NIR transmittance measurements, on the H-free a-Si investigated. Finally, the performed experiments are needed to have more confidence of quick and accurate optical-characterizations techniques, in order to find new applications of a-Si layers in optics and optoelectronics.

Evaluation of Chemical Bonding States in Multilayer Interconnect Structures for Thermal Management in Next Generation Very Large Scale Integration

1. Background and purpose Currently, it is expected that Ru is going to be introduced in place of Cu, which is the mainstream interconnect material in the very large scale integrated (VLSI) circuit. As high integration has been proceeding, the interconnect is expected not only having excellent electrical characteristics and reliability, but also providing an effective pathway for the removal of the heat generated by device operation [1]. The increasing current density in the narrowing interconnect produces Joule heat. The generated heat is removed by a heat sink attached to the substrate through the interconnect. Therefore, if the thermal resistance between the substrate and the interconnect is high, the heat cannot be removed efficiently and the interconnect temperature rises, lead to a degradation of VLSI reliability [2].In this study, we evaluated chemical bonding states of Ru/TaN/(SiOx/)Si stacking structure to clarify the mechanism contributing thermal resistance for the superior thermal management in VLSI. 2. Experimental method A 5 nm TaN was deposited by reactive sputtering (Deposition conditions: 25°C, 300 W, 1.0×10-5 Pa, Ta target) and subsequently 10 nm Ru was deposited by magnetron sputtering on a Si substrate with approximately 2 nm-thick native oxide. We prepared four samples with Ar:N2 gas ratios of 19:1, 17:3, 16:4, and 15:5, respectively, during the TaN deposition. The total thermal resistance was measured by the Frequency Domain Thermoreflectance (FDTR) method under vacuum condition.We also evaluated the chemical bonding states at the interface by Laboratory Hard X-ray Photoelectron Spectroscopy (Lab. HAXPES). The measurement conditions were kinetic energy of 9.25 keV, energy resolution of 0.5 eV, energy step of 50 meV, beam diameter of 50 μm2, and detectable depth of 50 nm, respectively. Au 4f was used as a reference of the energy calibration during for the analysis. 3. Results and Discussion The thermal resistance measured from the entire Ru/TaN/(SiOx/)Si stacking structure was reported by previous studies [1]. It can be seen that the thermal resistance decreases with the increase of N2 flow rate. In order to discuss the mechanism for determination of the thermal conductance, we performed nondestructive measurements by Lab. HAXPES.Figures 1 and 2 show the photoelectron spectra obtained from Ru 3d (Ar:N2=19:1, 15:5) and Si 1s (Ar:N2=19:1, 15:5), respectively. From Fig. 1, no significant change is observed in Ru 3d spectra even within the N2 gas flow rate changes. Therefore, the cause of the change in thermal resistance with the N2 gas flow rate change cannot be found at the Ru/TaN interface. On the other hand, from the Si 1s spectrum shown in Fig. 2, it can be confirmed that the peak intensity due to Si-N or Si-O-N bonds increases with increasing N2 gas flow rate. Therefore, it can be considered that the Si-N or Si-O-N bonds formed at the TaN/(SiOx/)Si interface as the N2 gas flow rate increased promoted heat transport and contributed to the reduction of thermal resistance.In summary, the important mechanism to control the thermal resistance became clear by the non-destructive evaluation of the chemical bonding states in the multilayer stacking structure using Lab. HAXPES. Acknowledgement This work was supported by the CREST under Project No. JPMJCR19Q5 of the Japan Science and Technology Corporation (JST).

Optimization of low resistivity molybdenum thin films for high-temperature microheater applications

In this paper, we discuss the optimal DC magnetron sputtering deposition conditions needed to obtain low resistivity Molybdenum (Mo) thin films for high-temperature (800 °C) microheater applications. The influence of Ar gas pressure (2–10 mTorr), sputtering power (80–160 W), and annealing temperature (200–1000 °C) on the resistivity and adhesive properties of Mo thin films were investigated. The structural, morphological, and electrical properties of as-deposited and annealed Mo thin films were characterized by X-ray diffraction, Scanning Electron Microscopy, Atomic Force Microscopy, and four-point probe techniques. The thin films deposited at 120 W, 6 mTorr, and annealed at 1000 °C showed low resistivity (18 μΩ-cm) and good adhesive properties. Suspended-membrane microheaters were fabricated using as-deposited and annealed Mo thin films, and their performance characteristics were compared. The impact of thin-film resistivity on power consumption and on the maximum operating temperature of Mo microheater was also investigated.

Structural and optical characteristics determined by the sputtering deposition conditions of oxide thin films.

The influence of film thickness on the structural and optical properties of silicon dioxide (SiO2) and zinc oxide (ZnO) thin films deposited by radio frequency magnetron sputtering on quartz substrates was investigated. The deposition conditions were optimized to achieve stoichiometric thin films. The orientation of crystallites, structure, and composition were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), while the surface topography of the samples was analyzed using scanning electron microscopy (SEM). The optical characteristics were measured for samples with the same composition but obtained with different deposition parameters, such as increasing thickness. The optical constants (i.e., the refractive index n, the extinction coefficient k, and the absorption coefficient α) of the SiO2 and ZnO oxide films were determined from the transmission spectra recorded in the range of 190–2500 nm by using the Swanepoel method, while the energy bandgap was calculated from the absorption spectra. The influence of thickness on the structural and optical properties of the oxide films was investigated. Good optical quality and performance were noticed, which makes these thin films worthy of integration into metamaterial structures.

Physical principles of radio-frequency magnetron sputter deposition of calcium-phosphate-based coating with tailored properties

The influence of radio-frequency (RF) magnetron sputter deposition conditions (RF power discharge density, working gas atmosphere, deposition time, and electrical substrate bias) on the properties (microstructure, texture, Ca/P ratio) of nanocomposite calcium-phosphate (CaP) coatings has been reported. A phenomenological model was developed to explain the formation of the RF magnetron sputter-deposited hydroxyapatite (HA) coating depending on the various deposition conditions. In the initial deposition stages, a nanocrystalline or quasi-amorphous CaP layer is formed. As both the film thickness and temperature gradient across the film thickness increased, the crystallisation of the HA phase occurred, which led to the formation of the fibre 〈002〉 texture in the films. The increase in the coating thickness also resulted in an increase in the grain size and a decrease in the residual microstress. The cross-section of the coating revealed a polycrystalline fibre structure with wedge-shaped columns. The addition of water vapour to an Ar atmosphere allowed to restore the hydroxyl groups in the composition of the HA coatings. The topography of the СaP coating surface that had irregular grains with different form and shape grown out of the coating plane was established, which extended the well-known structural zone models (Thornton, Monsieur, Movchan and Demchishin, Anders, etc.) and was formed both at a relatively low substrate temperature of 160–200 °С and RF power level when the substrate was bombarded with positive ions with an energy of ~100 eV, regardless of the working gas atmosphere used (argon or oxygen), resulting in a the growth of a coating with a preferably amorphous or nanocrystalline structure.

Superior control for physical properties of sputter deposited ITO thin-films proper for some transparent solar applications

Superior control of sputtering deposition of ITO thin-films to enhance the physical properties of the ITO thin-films has been investigated. The effect of different sputter deposition conditions and the thermal post-annealing on the physical properties of the transparent-conductive indium tin oxide (ITO) thin-films deposited on a glass substrate have been studied. The power varied from 20 to 210 W with argon (Ar) gas flowing at a rate from 20 to 80 sccm. Thermal post-annealing of deposited thin-films at 200–450 °C in vacuum and air has been carried out as well. The physical properties were monitored using XRD, STM, four-point probe electrometer, and UV–Vis spectrometer. The change of the Ar flow rates influences the deposited films surface roughness, electrical sheet resistance (Rs), average optical transmittance (Tavg) with no apparent change in the morphology fractal dimension. At the Ar flow rate of 30 sccm and the critical power of 120 W, the deposited thin-films transform from amorphous to semi-crystalline structure mostly up 170 W. Optimal thin-films with fairly the highest Tavg at 97.7% and good Rs with 158.3 Ω/sq could be obtained under a residual Ar gas flow rate of 50 sccm and at 20 W. The critical post-annealing temperature at 350 ℃ (air) and 450 °C (vacuum) could initiate the semi-crystalline structure of the previously amorphous deposited thin-films. For the first time, ITO thin-films with Tavg and Tmax up to 97.7% and 99.9% respectively have been achieved. Besides, the Rs value is controlled from 6 to 3981 Ω/sq with excellent average transparency. These prove viable candidates in transparent solar applications.

RF magnetron sputtering induced the perpendicular magnetic anisotropy modification in Pt/Co based multilayers* *Project supported by the National Key R&D Program of China (Grant No. 2017YFB0405700), the National Natural Science Foundation of China (Grant Nos. 11474272 and 61774144), Beijing Natural Science Foundation Key Program, China (Grant No. Z190007), and the Chinese Academy of Sciences (Grant Nos. QYZDY-SSW-JSC020, XDB44000000, and XDB28000000).

We demonstrate that radio frequency (RF) magnetron sputtering technique can modify the perpendicular magnetic anisotropy (PMA) of Pt/Co/normal metal (NM) thin films. Influence of ion irradiation during RF magnetron sputtering should not be neglected and it can weaken PMA of the deposited magnetic films. The magnitude of this influence can be controlled by tuning RF magnetron sputtering deposition conditions and the upper NM layer thickness. According to the stopping and range of ions in matter (SRIM) simulation results, defects such as displacement atoms and vacancies in the deposited film will increase after the RF magnetron sputtering, which can account for the weakness of PMA. The amplitude changes of the Hall resistance and the threshold current intensity of spin orbit torque (SOT) induced magnetization switching also can be modified. Our study could be useful for controlling magnetic properties of PMA films and designing new type of SOT-based spintronic devices.

Magnetically Induced Enhanced Exchange Spring Effect in CoFe₂O₄/CoFe₂/CoFe₂O₄ Films

Earlier, we reported exchange coupling between bilayers of CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , where CoFe2O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> are the hard and soft magnetic layers, respectively. These results suggested trilayers structures of CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> are strong candidates for low hysteresis loss “exchange spring materials.” To study this possibility, we extended our investigation to the synthesis of CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> trilayers under different sputtering deposition conditions, which included oxygen pressure in the case of the CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> component and the application of a magnetic field during the deposition of the soft CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The most significant finding was an increase in the exchange spring figure of merit (FoM) of 36% in-plane and 60% out-of-plane by the application of an applied field during the deposition of the soft CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , resulting in a decrease in hysteretic losses by a similar percentage. We will discuss these spin spring results in terms of an increase in uniaxial anisotropy energy in the CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layers due to short-range ordering of Fe-Fe and Co-Co pairs during deposition and an enhancement in the coercivity and remnant magnetization of CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> . We also discuss a metric (FoM) for describing enhancements due to multiple optimized deposition conditions.

Radio Frequency Plasma-Enhanced Reactive Magnetron Sputtering Deposition of α-SiN x on Photonic Crystal-Laser Diodes for Facet Passivation.

Amorphous silicon nitride (α-SiNx) films were coated on a photonic crystal-laser diode by the radio frequency magnetron sputtering method. Sputtering deposition conditions were changed to obtain α-SiNx films with different properties. The optical parameters and morphologies of the products were systemically characterized by spectroscopic ellipsometry fitting, energy-dispersive X-ray spectroscopy, atomic force microscopy, and performance of LDs coated with α-SiNx films were tested at 25 °C. Physical mechanisms of sputtering were explained in detail. α-SiNx with a band gap of 4.4 eV and a refractive index of 2.03 at 980 nm were grown. The extinction coefficient equal to 0 at 980 nm, and the surface morphology tended to be homogeneous and dense. The main influencing factors related to the catastrophic optical mirror damage (COMD) phenomenon were investigated. Then plasma pretreatment was implemented to eliminate defects and improve the cavity surface quality and further optimized by measuring the intensity of photoluminescence. Afterward, a rapid annealing method was also carried out to improve coating performance. Finally, α-SiNx acted as a passivation layer in the antireflection film coated on the LD facet, and the COMD threshold increased from 5 to 15.2 W, which led to a higher reliability than nonoptimized LDs and elimination of the COMD phenomenon.

Identification of defect species in ZnO thin films through process modification and monitoring of photoluminescent properties

Photoluminescence (PL) from defect-rich ZnO thin films was investigated in relation to transparent conductive properties. By varying the sputter deposition and post-treatment conditions, the correlation between deep-level luminescence and changes in the optical and electrical properties was examined, and the defects that were the origin of the donors and acceptors were identified. Slightly oxygen-deficient and transparent conductive films deposited on glass substrates without a supply of oxygen source gas had a resistivity of 3 × 10−3 Ω cm; these films exhibited only band edge emissions peaking at 380 nm in the PL spectra. Abundant defects were introduced through postannealing in an H2 atmosphere at 300−400 °C. The permeating H2 reacted with the O and Zn atoms constituting the crystal network, and the resulting PL spectra exhibited a continuous defect-emission band ranging from violet to red. The spectra included transitions of the conduction band (CB) → zinc vacancies (VZn) (400 nm), zinc interstitials (Zni) → valence band (VB) (440 nm), CB → oxygen vacancies (VO) (560 nm), and CB → oxygen interstitials (Oi) (620 nm). Similar PL spectra from disordered crystals were obtained by sputter deposition at 300 and 400 °C under a reducing atmosphere. The films deposited on the sapphire substrate above 300 °C were nonemissive because they were strongly oxygen deficient compared to those on the glass substrate. When the films on sapphire were postannealed, only emissions from the CB → VO transition appeared. Thus, VO is the primary defect in films on sapphire, whereas every type of intrinsic defect (Zni, Oi, VO, and VZn) builds up in ZnO films on glass. Electronically excited modifications induced by argon plasma irradiation were investigated in order to discriminate the influence from that of thermal processes. After prolonged plasma exposure, emissions corresponding to CB → VO (540 nm) and Zni → VB (420−470 nm) transitions predominated as a result of preferential sputtering of oxygen atoms. The improvement in electric conduction by the plasma treatment is attributed to hydrogen atoms trapped at newly created VO sites.

Multistep magnetron sputtering process and in-situ heat treatment to manufacture thick, fully oxidized and well crystallized YSZ films

In this work, yttria stabilized zirconia electrolyte layers were deposited by reactive pulsed DC magnetron sputtering on various substrates (i.e. silicon wafer, glass plates, NiO/YSZ cermets). The sputtering process was studied by following the cathode voltage and gas pressure evolutions with the reactive flow rate. The substrate temperature was found to play a role on the transition between the elemental and reactive sputtering modes. The influence of the sputtering parameters and deposition conditions on the film properties was investigated. Thick (about 2 μm) and dense deposits were manufactured both in elemental and in reactive sputtering modes. Ex-situ and in-situ heat treatments were applied to promote crystallization and oxidization of the deposits. The oxygen content was evaluated by Rutherford backscattering spectroscopy before and after heat treatments which confirmed that fully oxidized material was obtained. Optical transmission measurements on deposits synthesized on glass slides were also performed for a cross check of the oxidation state. X-ray diffraction technique revealed that heating of the substrate is necessary to get a crystallized as-deposited film. However, further annealing is required to synthesize the desired YSZ cubic phase. It has been proved that with the proposed multistep process including in-situ short heating steps, thick YSZ films could be synthesized without any stress cracking as usually observed after complete oxidation. Those films have shown very low leakage rate (6.67 × 10−4 mbar·l·s−1) which is required for the application.

Electrical, structural, and topographical properties of direct current (DC) sputtered bilayer molybdenum thin films

Renewable energy sources offer a viable green energy solution to the increasing global energy demands, and the photovoltaics offers a means of tapping into the abundance of the solar energy. Molybdenum (Mo) thin film has been used as a back-contact electrode in high-efficiency solar cells mainly due to its ohmic nature with the absorber material (especially with chalcopyrites and kesterites), low resistivity, adequate reflectance, and porosity to alkali materials. Mo thin films used in solar cells are deposited by direct current (DC) sputtering under argon ion atmosphere. The present work deals with the effects of the sputtering deposition conditions (i.e., working pressure and power) on the electrical properties of Mo thin films deposited on soda-lime glass using DC magnetron sputtering at different working pressures (5–20 mTorr) and deposition powers (100–800 W). Optimized deposition power and sputtering pressure were used to deposit a Mo bilayer thin film intended for solar cells application. X-ray diffractometric studies showed the (110) plane corresponding to the body-centered cubic structure of the Mo material. Calculated values were used to estimate other parameters of the deposited films (e.g., stress, dislocation density), as these properties affect the potential diffusion of sodium (Na) through the soda-lime glass into the absorber layer that is important as the moderate inclusion of Na improves the cell efficiency. The cross-section of the deposited film was analyzed using a field-emission scanning electron microscopy, to confirm the successful deposition of the bilayer. The surface of the films plays a vital role in the Mo interface with the absorber layer. Atomic force microscopy was used to acquire the topographical information from the sputtered bilayer film. The resistivity, as measured using a four-point probe, of the Mo films deposited at different conditions was in the order of 10−6 Ω m while the resistivity of the bilayer was 0.60 × 10−6 Ω m.

Thin-film X-ray filters on microstructured substrates and their thermophysical properties

It is shown that structured substrates having micron- or submicron-sized through holes and coated with an ultrathin organic film can be used for the fabrication of thin-film X-ray filters via direct growth of functional layers on a substrate by sputter deposition, without additional complex processing steps. An optimised process is considered for the fabrication of X-ray filters on support structures in the form of electroplated fine nickel grids and on track-etched polymer membranes with micron- and submicron-diameter through pores. ‘Optimisation’ is here taken to mean matching the sputter deposition conditions with the properties of substrates so as to avoid overheating. The filters in question are intended for both imaging and single-channel detectors operating in the soft X-ray and vacuum UV spectral regions, at wavelengths from 10 to 60 nm. Thermal calculations are presented for the heating of ultrathin layers of organic films and thin-film support substrates during the sputter deposition of aluminium or other functional materials. The paper discusses approaches for cooling thin-film composites during the sputter deposition process and the service of the filters in experiments and gives a brief overview of the works that utilised filters produced by the described technique on microstructured substrates, including orbital solar X-ray research in the framework of the CORONAS programme and laboratory laser plasma experiments.

Effect of ITO film deposition conditions on ITO and CdS films of semiconductor solar cells

Inorganic metal chalcogenide compounds based thin-film solar cells are regarded as most promising candidates for film power modules due to their high efficiencies with low cost. From top to bottom, the semiconductor thin film solar cell is made up of a metal layer, an absorber material, a buffer layer, and a transparent conducting oxide (TCO). Indium tin oxide (ITO) is a common material for transparent conducting films used as a front contact layer on solar cells. Although extensive studies have been performed on the deposition and properties of ITO films, few studies focused on the effect of the sputtering deposition conditions of ITO on the buffer layer. In this study, ITO thin films were deposited on soda-lime glass (SLG) by conventional RF-magnetron sputtering. The dependence of the electrical and crystalline properties on different substrate temperature, different RF power and different introducing rate of oxygen was investigated. The deposition conditions of ITO not only have influences on the structure and properties of ITO but also affect the buffer layer underneath. Therefore, we investigated the effect of ITO deposition parameters on the crystallization and electrical and optical properties of sputtered CdS films and, in turn, on the resulting device characteristics.