Radio Frequency Reactive Magnetron Sputtering Research Articles

Moderate temperature deposition of RF magnetron sputtered SnO2-based electron transporting layer for triple cation perovskite solar cells

The perovskite solar cells (PSCs) are still facing the two main challenges of stability and scalability to meet the requirements for their potential commercialization. Therefore, developing a uniform, efficient, high quality and cost-effective electron transport layer (ETL) thin film to achieve a stable PSC is one of the key factors to address these main issues. Magnetron sputtering deposition has been widely used for its high quality thin film deposition as well as its ability to deposit films uniformly on large area at the industrial scale. In this work, we report on the composition, structural, chemical state, and electronic properties of moderate temperature radio frequency (RF) sputtered SnO2. Ar and O2 are employed as plasma-sputtering and reactive gases, respectively. We demonstrate the possibility to grow a high quality and stable SnO2 thin films with high transport properties by reactive RF magnetron sputtering. Our findings show that PSC devices based on the sputtered SnO2 ETL have reached a power conversion efficiency up to 17.10% and an average operational lifetime over 200 h. These uniform sputtered SnO2 thin films with improved characteristics are promising for large photovoltaic modules and advanced optoelectronic devices.

Impact of the RF Power on the Copper Nitride Films Deposited in a Pure Nitrogen Environment for Applications as Eco-Friendly Solar Absorber

This material can be considered to be an interesting eco-friendly choice to be used in the photovoltaic field. In this work, we present the fabrication of Cu3N thin films by reactive radio-frequency (RF) magnetron sputtering at room temperature, using nitrogen as the process gas. Different RF power values ranged from 25 to 200 W and gas pressures of 3.5 and 5 Pa were tested to determine their impact on the film properties. The morphology and structure were exhaustively examined by Atomic Force Microscopy (AFM), Fourier Transform Infrared (FTIR) and Raman Spectroscopies and X-ray Diffraction (XRD), respectively. The AFM micrographs revealed different morphologies depending on the total pressure used, and rougher surfaces when the films were deposited at the lowest pressure; whereas FTIR and Raman spectra exhibited the characteristics bands related to the Cu-N bonds of Cu3N. Such bands became narrower as the RF power increased. XRD patterns showed the (100) plane as the preferred orientation, that changed to (111) with the RF power, revealing a worsening in structural quality. Finally, the band gap energy was estimated from transmission spectra carried out with a Perkin Elmer 1050 spectrophotometer to evaluate the suitability of Cu3N as a light absorber. The values obtained demonstrated the capability of Cu3N for solar energy conversion applications, indicating a better film performance under the sputtering conditions 5.0 Pa and RF power values ranged from 50 to 100 W.

Effect of Argon on the Properties of Copper Nitride Fabricated by Magnetron Sputtering for the Next Generation of Solar Absorbers.

Copper nitride, a metastable semiconductor material with high stability at room temperature, is attracting considerable attention as a potential next-generation earth-abundant thin-film solar absorber. Moreover, its non-toxicity makes it an interesting eco-friendly material. In this work, copper nitride films were fabricated using reactive radio frequency (RF) magnetron sputtering at room temperature, 50 W of RF power, and partial nitrogen pressures of 0.8 and 1.0 on glass and silicon substrates. The role of argon in both the microstructure and the optoelectronic properties of the films was investigated with the aim of achieving a low-cost absorber material with suitable properties to replace the conventional silicon in solar cells. The results showed a change in the preferential orientation from (100) to (111) planes when argon was introduced in the sputtering process. Additionally, no structural changes were observed in the films deposited in a pure nitrogen environment. Fourier transform infrared (FTIR) spectroscopy measurements confirmed the presence of Cu-N bonds, regardless of the gas environment used, and XPS indicated that the material was mainly N-rich. Finally, optical properties such as band gap energy and refractive index were assessed to establish the capability of this material as a solar absorber. The direct and indirect band gap energies were evaluated and found to be in the range of 1.70-1.90 eV and 1.05-1.65 eV, respectively, highlighting a slight blue shift when the films were deposited in the mixed gaseous environment as the total pressure increased.

Comprehensive growth and characterization study of GeOx/Si

In this study, the reactive radio frequency magnetron sputtering (RFMS) method under varying thickness was used to deposit GeOx on Si substrate at room temperature. The effect of thickness on the structural and optical properties of high-quality germanium dioxide (GeO2) thin films have been investigated by experimental. Structural properties were investigated using X-ray diffraction. It has been observed that the peak intensity of (113) reflection is the highest in the spectrum of 240.22 nm thickness and using scanning electron microscope (SEM) to calculate thickness of different samples. Reflection measurement, which is one of its optical properties, was measured with an optical spectrophotometer. It has been observed that as the thickness increases, the total reflectance changes. The absorption coefficient was calculated using the diffuse reflection curve. From this point of view, the energy band gap was calculated and it was seen that it varies between 4.1 eV and 4.4 eV. As a result, it was observed that the energy band gap increased as the thickness increased. And using spectroscopic ellipsometry to calculate the thickness of different, refractive index, extinction coefficient, and oscillator parameters. The oscillator energy decrease as the thickness of films increases and the dispersion energy increase with the increase of thickness. It have been observed that the thickness varies between 174.29 nm and 332.16 nm. The refractive index increases as the thickness increases.

Study of wide bandgap SnOx thin films grown by a reactive magnetron sputtering via a two-step method

In the present work, we report on the microstructural and optoelectronic properties of SnOx thin films deposited by a reactive radio frequency magnetron sputtering. After SnOx growth by sputtering under O2/Ar flow, we have used three different treatment methods, namely (1) as deposited films under O2/Ar, (2) vacuum annealed films ex-situ, and (3) air annealed films ex-situ. Effects of the O2/Ar ratios and the growth temperature were investigated for each treatment method. We have thoroughly investigated the structural, optical, electrical and morphology of the different films by several advanced techniques. The best compromise between electrical conductivity and optical transmission for the use of these SnOx films as an n-type TCO was the conditions O2/Ar = 1.5% during the growth process, at 250 °C, followed by a vacuum post thermal annealing performed at 5 × 10–4 Torr. Our results pointed out clear correlations between the growth conditions, the microstructural and optoelectronic properties, where highly electrically conductive films were found to be associated to larger grains size microstructure. Effects of O2/Ar flow and the thermal annealing process were also analysed and discussed thoroughly.

Investigation of Optimum Deposition Conditions of Radio Frequency Reactive Magnetron Sputtering of Al0.7Sc0.3N Film with Thickness down to 20 nm

AbstractFerroelectric aluminum scandium nitride (Al0.7Sc0.3N) has attracted increasing interest due to its high remanent polarization (Pr, >100 µC cm−2) and coercive field (Ec, >5 MV cm−1). The four radio frequency reactive magnetron sputtering conditions (sputtering power, N2 flow ratio, pressure, and temperature) influence the ferroelectric and material properties of 45 nm‐thick Al0.7Sc0.3N deposited on the TiN/SiO2/Si substrate. Crystallinity is enhanced under the deposition conditions with higher adatom energy but deteriorates when the growth condition increases over the optimum. The well‐crystallized films have (002)‐preferred orientation with the in‐plane compressive stress imposed by the peening effect and thermal stress. The imposed compressive stress increases the c0/a0 value, where c0 and a0 mean the c‐ and a–axis lattice parameters, which eventually increases the Ec of the film. Pr increases with the c0/a0 value, but other factors also influence the change. The films with high oxygen concentration show the wake‐up properties due to the large percentage of domain walls and their depinning. Finally, ferroelectricity is confirmed with films down to a thickness of 20 nm. However, the thinnest film shows a higher Ec and lower Pr. These findings imply the presence of non‐ferroelectric interfacial layers, which induce the depolarization effect.

Improved frequency response of the 3.5 GHz SMR devices using Ga-doped AlN thin films as the piezoelectric layers

In this paper, the aluminum nitride (AlN) and gallium-doped aluminum nitride (AlGaN) films are adopted to fabricate the 3.5 GHz solidly mounted resonator (SMR) devices. A reactive radio frequency (RF) magnetron sputtering system and a co-puttering subsystem were used to deposit AlN and AlGaN thin films as piezoelectric layers. The sputtering parameters were fixed as sputtering pressure of 35 mTorr and sputtering power of 200 W for AlN piezoelectric layers. For the co-sputtering parameters, the sputtering pressure was set 10 mTorr, and the sputtering powers of Al and GaN targets were 175 W and 25 W, respectively, to deposit AlGaN piezoelectric layers. The X-ray diffraction (XRD) patterns showed that as compared with the 2[Formula: see text] values of the diffraction peaks of AlN thin films, those of AlGaN thin films shifted to lower values. Even the diffraction intensity of (002) peak of AlGaN thin film was higher than that of AlN film, both AlN and AlGaN thin films presented the strongly [Formula: see text]-axis orientated crystallization. The energy dispersive X-ray spectrometer (EDS) analysis showed that the content of Ga element in the AlGaN thin film, ([Formula: see text]), was about 19%. SEM images showed that the obtained AlN and AlGaN thin films exhibited uniform grain sizes and smooth surfaces. Finally, both the frequency responses of the fabricated SMR devices were measured using a network analyzer and the difference in their efficiencies were well compared. The frequency response of the fabricated SMR device with [Formula: see text][Formula: see text]N thin film showed the center frequency of 3.51 GHz, the return loss [Formula: see text] of −10.466 dB, quality factor [Formula: see text] of 170.952, electromechanical coupling coefficient [Formula: see text] of 4.026%, and FoM value of 6.838, respectively. The results show that the frequency response of SMR device has been improved by Ga doped in AlN thin film, although the [Formula: see text] value is still less than that of obtained using single crystalline AlGaN thin film.

Chemical cyanide treatment of polycrystalline p-Cu2O/n-ZnO solar cell

Cuprous oxide (Cu2O) and zinc oxide (ZnO) hold a very crucial position in the field of materials research because of their immense potential in many acoustic, electronic and optical applications. Cu2O is a direct-gap semiconducting material with forbidden energy gap around 2.0 eV. It has been considered as one of the most promising materials for photovoltaic applications, especially for use at the top in a cascade cell structure. The enchantment of Cu2O and ZnO as photovoltaic materials is due to fact that their constituent materials are nontoxic, abundantly available and of relatively low cost. In this work, Cu2O thin films in polycrystalline form were prepared in radio-frequency (rf) reactive magnetron sputtering route on glass substrates at different substrate temperatures. After the samples were prepared, these were taken through a crown-ether cyanide (CN) treatment. Presence of oxygen in excess compared to stoichiometry is the major active impurity in Cu2O and consequently holes are the majority charge carriers in it. With the aid of crown-ether cyanide treatment of the prepared samples, hole-mobility was found to increase and resistivity was found to decrease considerably. Finally, polycrystalline p-Cu2O/n-ZnO heterojunctions were fabricated for use in solar cells. Results of Hall measurement strongly support the observations made from DLTS studies and photocurrent measurements. Thus, our present study confirms the improvement of device performance of the p-Cu2O /n-ZnO heterojunctions on chemical cyanide treatment.

Anti-corrosion performance of the conductive bilayer CrC/CrN coated 304SS bipolar plate in acidic environment

A bilayer CrC/CrN coating prepared on 304 stainless steels (304SS) using reactive radio frequency magnetron sputtering technique (RF-MS) is investigated in acidic fuel cell environment. Compared to the CrN monolayer, the synergistic function of bilayer structure effectively hinder penetration of corrosive substance through defects, significantly increases anti-corrosion of substrate. This is attributed to the increased compactness of coating and the good matching between layers to effectively enhance interfacial adhesion. Interfacial contact resistance (ICR) of the CrC/CrN covered 304SS is lower than that of substrate. These effects are closely associated with inherent characteristic and combined preparation method of the coating.

Dopant concentration influence on the optical properties of NiO thin films doped by Al and Nb deposited by DC and RF magnetron sputtering

Dopant concentration influence on the optical properties of NiO thin films doped by Al and Nb deposited by DC and RF magnetron sputtering

Effects of electronic structure and magnetic performance at the surface/interface of r-GO and TiO2 in r-GO/TiO2 composite thin films: X-ray absorption near-edge structure and x-ray photoelectron spectroscopy

Titanium dioxide (TiO2) and reduced graphene oxide (r-GO) were synthesized separately by the radio frequency reactive magnetron sputtering technique on a Si-substrate (TiO2/Si) and the improved Hummers method, respectively. For deposition of r-GO onto TiO2, an aqueous solution of r-GO was deposited on the TiO2/Si thin film by the spin coating process to fabricate the (r-GO/TiO2)/Si composite thin-film. The (r-GO/TiO2)/Si composite thin-film is characterized using different spectroscopic techniques to study the effects at the interface of TiO2 and r-GO in the surface defects, vacancy, incorporation of the different oxygenated moiety, microstructural, surface morphological, electronic, and magnetic performance. Our motivation is to contribute and understand mainly the tuning of the electronic structure and magnetic performance of the (r-GO/TiO2)/Si composite structure for the development of future promising optoelectronic and spintronic applications. We found that the magnetic performance is improved due to the change in the electronic properties of r-GO deposited on TiO2 thin films. Thus, the role of the interfacial defects in the (r-GO/TiO2)/Si thin film and the mechanism of the tuning of the electronic structure and magnetic performance are elucidated comprehensively.

Highly transparent conductive F-doped SnO2 films prepared on polymer substrate by radio frequency reactive magnetron sputtering

F-doped SnO2 (FTO) films have excellent optical-electrical properties and have been widely used, but the preparation of FTO film on the surface of flexible polymer substrate by magnetron sputtering has not been reported. In this study, Sn-SnF2 mixture was used as the target, and then the FTO film was prepared by reactive magnetron sputtering on the surface of the polyethylene terephthalate substrate at substrate temperature of room temperature, 60 and 100 °C. The results show that highly transparent conductive FTO films can be obtained by optimizing the O2 flow rate at each substrate temperature. In general, as the substrate temperature increases, the optimized range of O2 flow rate shifts to the direction of lower O2 flow rate and the corresponding transparent conductive properties are slightly enhanced. Currently, the films show sheet resistance of 209–423 Ω/sq., transmittance in visible-light range of 84.4–90.3% and figure of merit of 5.09–12.9 × 10–4 Ω–1, which is comparable with those of previously reported SnO2-based films. At the same time, the films have better bending performance at the bending radius of 20 mm, but they have poor damp-heat stability. In addition, the influence of substrate temperature and O2 flow rate on structure (thickness, crystallinity and surface roughness) and energy gap of the films is also investigated.

High-Temperature Ferroelectric Behavior of Al0.7Sc0.3N.

Currently, there is a lack of nonvolatile memory (NVM) technology that can operate continuously at temperatures > 200 °C. While ferroelectric NVM has previously demonstrated long polarization retention and >1013 read/write cycles at room temperature, the largest hurdle comes at higher temperatures for conventional perovskite ferroelectrics. Here, we demonstrate how AlScN can enable high-temperature (>200 °C) nonvolatile memory. The c-axis textured thin films were prepared via reactive radiofrequency magnetron sputtering onto a highly textured Pt (111) surface. Photolithographically defined Pt top electrodes completed the capacitor stack, which was tested in a high temperature vacuum probe station up to 400 °C. Polarization–electric field hysteresis loops between 23 and 400 °C reveal minimal changes in the remanent polarization values, while the coercive field decreased from 4.3 MV/cm to 2.6 MV/cm. Even at 400 °C, the polarization retention exhibited negligible loss for up to 1000 s, demonstrating promise for potential nonvolatile memory capable of high−temperature operation. Fatigue behavior also showed a moderate dependence on operating temperature, but the mechanisms of degradation require additional study.

Effects of electron doping on the d0 magnetism in N-implanted ZnO and ZnAlO films

In this paper, N ions are implanted into ZnO and ZnAlO films with different carrier concentrations prepared by radio frequency reactive magnetron sputtering on sapphire substrates. The structural, electrical, optical and magnetic properties of N-doped and (Al, N) co-doped ZnO films is investigated, and the particular emphasis is placed on the effects of carrier concentration on the defects induced magnetism in the films. Our results show that all the doped ZnO films are ferromagnetic at room temperature. A trace amount of additional Al doping has a significant effect on the improvement of ferromagnetic properties, and a maximum saturation magnetization of 73 emu/cm3 is obtained for (Al, N) co-doped ZnO films. The optical band gaps of ZnO films increase with the increasing Al doping content, which is owing to the combined effect of high carrier concentration and the Burstein Moss effect. The average transmittance of all ZnO films exceeds 80%. Our results confirm that appropriate electron doping can effectively enhance the magnetic moment in N implanted ZnO which may also apply to other ZnO systems with d0 magnetism.

Synthesis and tribocorrosion performances of multilayer (Ta/ZrN)n coatings

Multilayer thin coatings (∼3 µm in thickness) were deposited using reactive radio frequency magnetron sputtering on Ti-6Al-4 V substrate for biomaterial applications. Films are a combination of hard zirconium nitride with pure tantalum, used to manage interfacial stress and to avoid crack growth. Alternating hard/ductile material is a biomimetic design inspired by nature (nacre-inspired materials). Tribocorrosion tests were performed in Hank's solution at 37 °°C, under open circuit potential by using a ball-on-disk reciprocating tribometer. A tendency to high resistance against corrosion was found for all the samples. Coatings with a top 100 nm thick ZrN layer showed more noble potential as well as a reduction of both the friction coefficient and the wear rate during the sliding phase. The principal wear mechanism is related to a tribocorrosion layer formation.

Natural preparation of rice husk-derived silica and eggshell-derived calcium carbonate composite as a coating material for dental implant

Background: The world is in front of two emerging problems being scarceness of virgin re-sources for bioactive materials and the gathering of waste production. Employment of the surplus waste in the mainstream production can resolve these problems. The current study aimed to prepare and characterize a natural composite CaO-SiO2 based bioactive material derived from naturally sustained raw materials. Then deposit this innovative novel bioactive coating composite materials overlying Yttria-stabilized tetragonal zirconia substrate. Mate-rials and method; Hen eggshell-derived calcium carbonate and rice husk-derived silica were extracted from natural resources to prepare the composite coating material. The manufac-tured powder was characterized via Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), X-ray fluorescence (XRF), X-ray diffraction (XRD) and particle size analyzer. The bioactive composite was deposited through radiofre-quency (Rf) reactive magnetron sputtering overlying disc-shaped samples with a dimension of 10 mm diameter were prepared from partially sintered Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). Results: The particle size of the rice husk-derived ranged between (480.4 – 606.1) nm with a mean particle diameter of 541 nm. The eggshell derived calcium carbonate powder presented a particle size between (266.4-336) nm and a mean particle diameter of 299.9 nm. The XRD data revealed the crystalline nature and phase composition of the natural prepared calcium carbonate powder and demonstrate the monocrystalline nature of natural SiO2. FTIR spectrometer showed the emergence of novel spectra separated from the two innovative components. XRF analysis revealed that 99.4% of the rice husk is SiO2 while eggshell-derived powder is mainly composed of calcium oxide. Fe-SEM images of the coated zirconia exhibited average thickness of the natural CaCO3/SiO2 coat layer may reach to12.84 µ. Conclusion: The prepared composite derived from natural resource waste is suitable to be utilized as a coating material for ceramic dental implants with promising biological and mechanical properties.

Mechanical, tribological and anti-corrosion properties of AlCrNbSiTi high entropy coatings with various nitrogen fluxes and application to nickel-based alloy milling

(AlCrNbSiTi)N high entropy alloy coatings were prepared by reactive radio-frequency magnetron sputtering with nitrogen fluxes in the range of 0–20 sccm. The effects of the nitrogen flux on the microstructure, mechanical properties, phase composition, chemical bonds, tribological properties, corrosion resistance, and machining performance of the coatings were systematically examined and compared. All of the coatings exhibited an amorphous structure due to the high mixing entropy effect and large atomic-size difference of the coating elements. The coating hardness increased with an increasing nitrogen flux and reached a value of 43.7 GPa at a flux of 15 sccm. However, a significant reduction in the adhesion strength occurred at a nitrogen flux of 20 sccm as the result of a high residual compressive stress within the coating. The coating deposited with a nitrogen flux of 15 sccm showed the lowest wear rate (0.4 × 10−6 mm3/N·m) and corrosion current density (0.27 × 10−7A/cm2) of the tested coatings. The superior tribological performance of the coating was attributed to its high hardness-to-elastic modulus ratio, high hardness cubed-to-elastic modulus squared ratio, and low friction coefficient. Moreover, the improved anti-corrosion performance was the result of a large number of strong chemical bonds within the coating and the high adhesion strength. Finally, the milling test results showed that the addition of nitrogen with a flux of 15 sccm during the deposition process provided an effective reduction in the tool wear when machining Inconel 718 nickel-based alloy.

Electronic phase transition in CrN thin films grown by reactive RF magnetron sputtering

Chromium nitride thin films were prepared by reactive radio frequency magnetron sputtering on glass and Si(001) substrates. Thin films were grown at different nitrogen to argon flow rate ratio and their effect on the film composition, band gap and electronic phase transition was studied by different experimental technique. X-ray diffraction analyses establish that CrN films predominantly grow in [111]CrN and [002]CrN directions irrespective of the substrates used for the growths. The band gap was found to vary with the composition of the films. All films are semiconducting at room temperature and show discontinuity in their resistivity versus temperature curve indicating electronic transition. But the low temperature electronic phase depends on the growth conditions and composition of the films.

Enhanced Photocatalytic Activity of TiO2 Thin Film Deposited by Reactive RF Sputtering under Oxygen-Rich Conditions

TiO2 thin films are promising as photocatalysts to decompose organic compounds. In this study, TiO2 thin films were deposited by reactive radio-frequency (RF) magnetron sputtering under various flow rates of oxygen and argon gas. The results show that the photocatalytic activity decreases as the oxygen-gas ratio is increased to 30% or less, while the activity increases under oxygen-rich conditions. It was observed that the crystal structure changed from anatase to a composite of anatase and rutile, where the oxygen-gas ratio during RF sputtering is more than 40%. Interestingly, the oxygen vacancy concentration increased under oxygen-rich conditions, where the oxygen-gas ratio is more than 40%. The sample prepared under the most enriched oxygen condition, 70%, among our experiments exhibited the highest concentration of oxygen vacancy and the highest photocatalytic activity. Both the oxygen vacancies and the composite of anatase and rutile structure in the TiO2 films deposited under oxygen-rich conditions are considered responsible for the enhanced photocatalysis.

Optical optimization and thermal stability of SiN/Ag/SiN based transparent heat reflecting coatings

SiN/Ag/SiN heat reflecting coatings were prepared by radio frequency reactive magnetron sputtering on glass substrates. Properties of the coatings were comprehensively investigated in terms of optical property, surface morphology, microstructure and element distribution. It shows that SiN/Ag/SiN coating with the thickness of 30/15/55 nm exhibits a high visible transmittance of 74.6%, and a low infrared emittance of 3.0%. The thickness of Ag film has a significant effect on the spectral selectivity, while the thicknesses of SiN layers affect diffraction position or intensity of the spectrum weakly. The optical property of coating is basically unchanged after annealing in air at 200 ° C for 48 h, but fails over 300 ° C because of the mutual diffusion between Ag film and SiN layers. The high visible transmittance and low infrared emittance of the SiN/Ag/SiN coating makes it a promising candidate for energy conservation coatings.