Radio Frequency Magnetron Sputtering Research Articles

Thermally Induced Switching of Electrical and Optical Characteristics of VO2 Thin Nanostructured Films Fabricated by Radio Frequency Magnetron Sputtering

Thermally Induced Switching of Electrical and Optical Characteristics of VO2 Thin Nanostructured Films Fabricated by Radio Frequency Magnetron Sputtering

The evolution of preferred orientation and morphology of AlN films under various sputtering parameters

Wurtzite aluminum nitride (AlN) films with (100) and (002) preferred orientations are obtained on Si (100) wafers by radio frequency magnetron sputtering. The effects of target to substrate distance (TSD), RF power, deposition pressure and substrate temperature on crystal orientation and morphology of AlN films are analyzed. It is demonstrated that the TSD is the key factor affecting the preferred orientation of AlN films. The preferred orientation transforms from (002) to (100) with the increase of TSD. Further increase of substrate temperature and RF power causes the coexistence of (002) and (100) orientation. The evolution of orientation is explained by the change in kinetic energy of sputtered particles. The correlation between the crystal orientation and the surface morphology is investigated.

Photovoltaic performance of magnetron sputtered antimony selenide thin film solar cells buffered by cadmium sulfide and cadmium sulfide /zinc sulfide

Antimony selenide (Sb2Se3)-based thin-film solar cells have recently attracted worldwide attention as an abundant, low-cost, and efficient photovoltaic technology. The highest efficiencies recorded for Sb2Se3 solar cells have been obtained using cadmium sulfide (CdS) as a buffer layer. The Cd-included hybrid buffer layers could be one option to increase device efficiency through more effective usage of light. Therefore, in this work, the effect of single CdS and hybrid CdS/zinc sulfide (ZnS) buffer layers on the photovoltaic performance of Sb2Se3 thin-film solar cells has been investigated in detail. Sb2Se3 thin films have been deposited on molybdenum (Mo)-coated soda-lime glass (SLG) substrates by radio frequency magnetron sputtering technique followed by a post-heat treatment process. The morphological, and structural properties of Sb2Se3 thin films have been investigated by X-Ray Diffraction and Scanning Electron Microscopy. To compare the device performances of single CdS and hybrid CdS/ZnS buffered Sb2Se3 thin-film solar cells, SLG/Mo/Sb2Se3/CdS/ZnS/indium tin oxide (ITO) and SLG/Mo/Sb2Se3/CdS/ITO structures have been fabricated. The findings of this study have revealed a reduction in solar cells’ performance from η=3.93% for CdS buffer to η=0.13% for CdS/ZnS hybrid buffer. The change in the solar cell performance using the CdS/ZnS hybrid buffer has been discussed in detail.

Pure ultraviolet light-emitting diode based on the p-NiO/i-NiO/n-GaN structure by magnetron sputtering

Owing to its exceptional optical and electrical properties, NiO had gained considerable attention in the past few years. A broad spectrum of its applications was expected, particularly in light-emitting diodes (LEDs). NiO thin films were concocted using radio frequency (RF) magnetron sputtering, then this study systematically investigated the correlation between substrate temperature and the film properties. Exceptional NiO thin films with excellent characteristics were successfully obtained. Moreover, leveraging the optimized substrate temperature, we fabricated a p-NiO/i-NiO/n-GaN LED. With this configuration, p-NiO served as the hole transport layer, while i-NiO, obtained through rapid annealing, functioned as the electron barrier layer (EBL), thus avoiding the lattice mismatch between the hole transport layer and the EBL. It demonstrated pronounced diode rectification characteristics, manifesting an impressively low leakage current of 3.76 × 10−12 A. Furthermore, it achieved ultraviolet electroluminescence with a wavelength (∼375 nm) and a narrow FWHM (∼5 nm). Analysis revealed that the ultraviolet light emission in the diode predominantly originated from GaN-based near-band edge (NBE) luminescence.

CuFeO2 prepared by electron cyclotron wave resonance-assisted reactive HiPIMS with two magnetrons and radio frequency magnetron sputtering

In this study, thin films of CuFeO2 were prepared using radio frequency reactive sputtering (RF) and reactive high-power impulse magnetron sputtering combined with electron cyclotron wave resonance plasma (HiPIMS-ECWR). The plasma was characterized using an RF ion probe. Plasma density, tail electron energy, and electron temperature were extracted from the measured data. The films were deposited on fluorine-doped tin oxide-coated glass and quartz glass, with the substrates being heated during the deposition process. The final delafossite CuFeO2 structure was formed after annealing in an argon gas flow at 550–600 °C. The ideal deposition conditions were found to be with a stoichiometric ratio of Cu:Fe = 1:1, which was the optimal condition for creating the delafossite CuFeO2 structure. The measured optical bandgap of CuFeO2 was 1.4 eV. The deposited CuFeO2 films were subjected to photoelectrochemical measurements in the cathodic region to investigate their potential application in solar photocatalytic water splitting. The films showed photocatalytic activity, with a photocurrent density of around 70 μA/cm2 (under an incident light irradiation of 62 mW/cm2, AM 1.5 G). The electrochemical properties of the layers were studied using open circuit potential, linear voltammetry, and chronoamperometry. The surface morphology and chemical composition of the layers were analyzed by atomic force microscopy and energy-dispersive x-ray spectroscopy, respectively. The crystalline structure was determined using XRD and Raman spectroscopy. The results of these methods are presented and discussed in this article.

Optical, Electrical and Structural Properties of ITO/IZO and IZO/ITO Multilayer Transparent Conductive Oxide Films Deposited via Radiofrequency Magnetron Sputtering

In this study, we investigated the potential of multilayer TCO structures, specifically those made up of Indium Tin Oxide (ITO) and Indium Zinc Oxide (IZO), for crystalline silicon heterojunction solar cells (SHJ). We used the radiofrequency (RF) magnetron sputtering method to deposit various thin-film structures under various deposition temperatures and evaluated their electrical, optical, and morphological properties. The objective was to obtain films with lower sheet resistances and higher transmittances than those of single-layer thin films. Our results show that the ITO/IZO/ITO/IZO/ITO multilayer film structure deposited at 200 °C achieves the best sheet resistance of 18.5 Ohm/sq and a high optical transmittance of over 90% at a 550 nm wavelength. This indicates that multilayer TCO structures have the potential to be more optically and electrically efficient, and that they can improve the performance of optoelectronic devices. Finally, a power conversion efficiency of 17.46% was obtained for a silicon heterojunction (SHJ) solar cell fabricated using an ITO/IZO/ITO/IZO/ITO multilayer film structure deposited at 200 °C as a front TCO. Our study provides valuable insights into the field of TCOs and offers a promising avenue for future research.

Heteroepitaxial growth of β-Ga2O3 thin films on single crystalline diamond (111) substrates by radio frequency magnetron sputtering

In this work, we demonstrate the first achievement in heteroepitaxial growth of β-Ga2O3 thin films on single crystalline diamond (111) wafers using RF magnetron sputtering. A single monoclinic (β-phase) structure with a monofamily {01} plane was obtained. XRD pole figure shows (02) and (002) textures of the (01) β-Ga2O3 plane parallel to (111) diamond with six distinct rotational domains, confirming successful epitaxial growth. Collectively, this research provides valuable insights into the epitaxial growth of β-Ga2O3 on diamond via sputtering, paving the way for scalable β-Ga2O3/diamond heterostructures for future electronic and optoelectronic applications with not only high performance but also effective self-thermal management.

Effects of RF Magnetron Sputtering Power on the Mechanical Behavior of Zr-Cu-Based Metallic Glass Thin Films.

Zirconium-based metallic glass films are promising materials for nanoelectronic and biomedical applications, but their mechanical behavior under different conditions is not well understood. This study investigates the effects of radio frequency (RF) power and test temperature on the nanostructure, morphology, and creep behavior of Zr55Cu30Al10Ni5 metallic glass films prepared by RF magnetron sputtering. The films were characterized by X-ray diffraction and microscopy, and their mechanical properties were measured by a bulge test system. The results show that the films were amorphous and exhibited a transition from noncolumnar to columnar morphology as the RF power increased from 75 W to 125 W. The columnar morphology reduced the creep resistance, Young's modulus, residual stress, and hardness of the films. The creep behavior of the films was also influenced by the test temperature, with higher temperature leading to higher creep strain and lower creep stress. The findings of this study provide insights into the optimization of the sputtering parameters and the design of zirconium-based metallic glass films for various applications.

Aluminum doped zinc oxide thin films with lower activation energy prepared by radio frequency magnetron sputtering

Aluminum doped zinc oxide thin films with lower activation energy prepared by radio frequency magnetron sputtering

Effect of oxygen/argon ratio on microstructure, compositon and optical properties of erbium oxide anti-reflection films on CVD diamond

Optical erbium oxide (Er2O3) films were prepared by radio frequency (RF) magnetron sputtering to improve the infrared (IR) transmittance of chemical vapor deposition (CVD) diamond. This study aims to analyze the microstructure, composition and optical properties of Er2O3 anti-reflection films at various oxygen/argon ratios. Atomic force microscopy (AFM) analysis was used to detect the surface morphology of chemical oxidation CVD diamond and Er2O3 films. The surface roughness of Er2O3 films decreased with an increase in the oxygen/argon ratio. The crystalline structure of Er2O3 films was analyzed by using X-ray diffraction. Meanwhile, a gradual decrease was observed when the crystallite size and its strain were calculated. This was due to the transformation of partial phases from monoclinic to cubic structures. The chemical composition of Er2O3 films was analyzed by X-ray photoelectron spectroscopy (XPS). The surface of Er2O3 films underwent a transformation from the unstable structure of nonstoichiometric Er2O3-x to the stable structure of Er2O3 with an increase in the level of oxygen. Defect behavior was determined by transmission electron microscopy (TEM). Specifically, dislocation and twinning were observed at a high oxygen/argon ratio, which was mainly attributed to the competitive growth of polycrystalline Er2O3 films. The optical constants of Ψ and △ were shifted to lower wavelengths with increase oxygen/argon ratio. The maximum transmittance of the Er2O3/diamond film was 79% in the long-wavelength infrared (LWTR) range of 8–12 μm at an oxygen/argon ratio of 1:35. This value was significantly higher than that of the high oxygen/argon ratio. The present study concludes that a low oxygen/argon ratio promotes the growth and IR transmittance of Er2O3 films.

Homogeneity- and Stoichiometry-Induced Electrical and Optical Properties of Cu-Se Thin Films by RF Sputtering Power.

P-type Cu-Se thin films were deposited on glass substrates at room temperature using radio frequency magnetron sputtering by a single multi-component CuSe2 target. When using a multi-component target, the impact of the sputtering power on the homogeneity and stoichiometry within the thin films should be investigated in the depth direction to demonstrate a secondary effect on the electrical and optical properties of the thin films. Systematic characterization of the Cu-Se thin films, including the morphology, microstructure, chemical composition, and depth-directional chemical bonding state and defect structure of the thin films, revealed that the sputtering power played an important role in the homogeneity and stoichiometry of the thin films. At very low and very high sputtering power levels, the Cu-Se thin films exhibited more deviations from stoichiometry, while an optimized sputtering power resulted in more homogenous thin films with improved stoichiometry across the entire thin film thickness in the X-ray photoelectron spectroscopy depth profile, despite showing Se deficiency at all depths. A rapid decrease in carrier concentration, indicating a reduction in the net effect of total defects, was obtained at the optimized sputtering power with less deviation from stoichiometry in the Cu-Se thin films and the closest stoichiometric ratio at an intermediate depth.

Effect of yttrium doping on the photocatalytic properties of ZnO thin films

Zinc oxide films with different levels of yttrium doping are deposited on glass substrates, using radio-frequency magnetron sputtering. Photocatalytic properties were investigated for such Y-doping weight concentration: 0, 2.4, 3.9, 4.7 wt. %. The studies showed that the Y-doping significantly improves the photocatalytic activity of the ZnO thin films. It was shown that the ZnO:Y 3.9 wt. % presents the highest degradation efficiency of 100 % during 80 minutes and the largest rate constant 9.6 · 10-2 min-1 among all samples.

High performance IZO:P/IZO:Ni thin film transistor with double active layers

Staggered bottom-gate thin film transistor (TFT) with double active layers was successfully fabricated. IZO:P/IZO:Ni thin films were deposited on SiO2/p-Si substrate by radio frequency (RF) magnetron sputtering, IZO:P/IZO:Ni acted as double active layers. The optical transmittance of IZO: P and IZO:Ni thin films were over 80% in the wavelength of 400–800 nm. X-ray diffraction (XRD) patterns exhibited that the IZO:P and IZO:Ni films were amorphous under the annealing temperature of 265 ℃. Atomic force microscopy (AFM) images showed that IZO:P and IZO:Ni thin films had a low root-mean-square (RMS) roughness of 0.44 nm and 0.45 nm, respectively. The annealing temperature was 265 ℃, the obtained TFT with IZO:P/IZO:Ni double active layers structure showed excellent electrical properties, including a saturation mobility of 44.5 cm2 v−1 s−1, a threshold voltage of 1.3 V, a subthreshold swing of 0.35 V/dec, and an on/off current ratio of 3.8 × 108.

Effect of Post-thermal Annealing on the Structural, Morphological, and Optical Properties of RF-sputtered In2S3 Thin Films

Indium sulfide films were deposited by radio frequency magnetron sputtering technique on soda lime glass substrate. The deposition was conducted at the temperature of 150 °C and prepared films were then thermally annealed under argon atmosphere at 350 °C and 450 °C for 30 min. The impact of post-thermal annealing treatment on the properties of the films was investigated. From X-ray diffraction analysis, the formation of the stable tetragonal β-In2S3 crystal structure was substantiated and revealed that the thermal annealing treatment at 450 °C improved the crystallization of the films. The change in surface topographies and morphologies of the films depending on the post-thermal annealing process were examined by atomic force microscopy and scanning electron microscopy techniques, respectively. The stoichiometric ratio of constituent elements in the films was obtained by elemental analysis and it was seen that the films had slightly sulfur (S) deficit composition. It was found that the concentration of S slightly increased with the thermal annealing process. The room temperature photoluminescence spectra revealed that the films included vacancies of sulfur (VS: donor) and indium (In) (VIn: acceptor), indium interstitial (Ini: donor) and oxygen (O) in vacancy of sulfur (OVs: acceptor) defects with strong and broad emission bands at around 1.70, 2.20, and 2.71 eV.

Detection of biofuel adulterants using an optical fiber-based refractive index sensor

This study presents a Lossy Mode Resonance (LMR) based on fiber optic sensor for detecting biofuel adulteration. Tin Oxide (SnO2), coated over the clad removed portion of the optical fiber using the Radio Frequency Magnetron sputtering technique, was utilized as the sensing layer. The fabricated sensor probe was analyzed with various concentrations of the analytes that include methanol in ethanol, ethanol in methanol, methanol in water, ethanol in water, water in methanol, and water in ethanol. The absorption spectra of the fabricated sensor probe revealed two LMR peaks namely, LMR1 and LMR2 that exhibited wavelength shift under varying concentration of the analytes. The maximum sensor responses for the above combinations of the analytes were 4.95%, 3.30%, 3.00%, 3.56%, 2.91% and 3.57%, respectively. The sensitivities of the sensor probe towards these analytes were 0.46 nm/vol%, 0.17 nm/vol%, 0.49 nm/vol%, 0.58 nm/vol%, 0.08 nm/vol%, and 0.4 nm/vol%, respectively. The real time sample were examined using metal oxides coated sensors. The result exhibits SnO2 coated probe is sensitive than other probes.

Piezoelectric and magneto-optical effect of lanthanum-doped bismuth ferrite films on silicon substrate

Rhombohedral La:BiFeO3 films were successfully prepared on Si substrates by using Radio frequency magnetron sputtering method. The LaNiO3 as buffer layer is beneficial for improving the quality of the film, reducing surface roughness, and getting rid of the impure phase. The Bi0.9La0.1FeO3/LaNiO3/Si film has the largest piezoelectric coefficient with d33 reaching 4.76 pm/V, which is about 2.5 times larger than that of BiFeO3/LaNiO3/Si. The saturation magnetization and the MCD signal of BiFeO3 films are significantly enhanced by doping La3+. The MCD ellipticity of La:BiFeO3 film at 555 nm increase with the increase of La3+ concentration. Bi0.7La0.3FeO3/LaNiO3/Si film show strong magneto-optical effect with the high MCD ellipticity of 850 deg./cm, which is more than about 1.7 times larger than that of BiFeO3 film. This film is expected to be developed into a new multifunctional material with multi-field coupling of electro-opt-magnetism.

Nano indentation studies on ceramic thinfilms coatings deposited using sputtering process for energy applications

Nanoindentation technique is generally used for measuring thinfilm mechanical properties such as hardness, modulus and stiffness. Nanoindentation of ceramic thinfilms of SiO2, Si3N4 and Al2O3 was deposited by radio-frequency (RF) magnetron sputtering on the stainless steel (SS304) substrates using a nanoindenter. Under varied sputtering conditions, the “as-deposited” film was amorphous. The as-deposited thin film had a thickness of 200 nm. The amorphous film was loaded/unloaded only once while operating in load control mode. Hardness and Young's modulus, two mechanical properties of the ceramic thinfilms, were also measured. When SiO2, Si3N4, and Al2O3 thinfilms are deposited onto stainless steel substrates using an RF magnetron sputtering, the roughness of the ceramic thinfilms is in the range of 8 to 12 nm. The nanoindentation results were compared, the hardness of the coatings is in the range of 6 to 9 GPa, and these ceramic coatings can be used as an adhesive layer for multilayer thin film coating.

Physical properties of aluminum doped Zinc Oxide thin films and single wall carbon nanotubes bilayers with potential application in photovoltaics devices

A study of transparent thin films of Zinc Oxide doped with Aluminum (AZO) processed by sputtering with potentials application as substrate for single wall carbon nanotubes processing by spray-coating is discussed in this work. AZO Thin films have been deposited by radiofrequency magnetron sputtering technique at room temperature in high vacuum ambient and using an Argon atmosphere. The AZO thin films and the processed bilayers of Zinc Oxide: Aluminum/Single wall carbon nanotubes were characterized by scanning electron microscopy, Raman spectroscopy, x-ray diffraction, ultraviolet-visible spectrophotometry, stylus profilometry and four-terminal method for the electrical resistivity measurement. The feasibility of the Zinc Oxide doped with Aluminum thin films for its use as single wall Carbon Nanotubes substrate processed by a low-cost technique, with potential application in the configuration of photovoltaics devices is presented, analyzed and discussed as function of its electrical, morphological and optical properties through Haacke figure of merit quantification. A two-order reduction in resistivity values, average acceptable transmittance values (∼80%), and crystallinity expected for polycrystalline films were obtained for AZO/Single wall carbon nanotubes bilayers; although the homogeneity of the single wall carbon nanotubes distribution on AZO thin films processed by RF-Sputtering should be improved, the possible application as transparent electrode in a usual configuration of solar cells of AZO/Single wall carbon nanotubes can be performed.

The Surface Behavior of ZnO Films Prepared at Room Temperature

The surface behavior of ZnO-based films can be modulated via the postannealing and ultraviolet (UV) illumination of different strengths and durations, respectively. The present results could provide the basis for modulating their microstructures with respect to the grain-size distribution and photocatalytic behavior, and act as a potential guide in the field of wide-bandgap semiconducting oxides. ZnO films were prepared at room temperature onto Corning-1737 glass substrates by applying radio-frequency magnetron sputtering without supplying an oxygen source. With the purpose of obtaining modulational grain microstructures, the as-prepared ZnO films (Z0) were treated via a postannealing modification in a vacuum furnace at 300 °C for 30 min after deposition (Z300), accompanied by adjustable internal stress. The contact angle (CA) value of the ZnO films was reduced from 95° to 68°, owing to the different grain microstructure accompanied by a change in the size variation. In addition, UV light with different illumination strengths could be used to improve the hydrophilicity, which varied from a hydrophobic status to a superhydrophilic status due to the desirable surface characteristics of its photocatalytic action. In addition, the photocatalytic activity of the ZnO films exhibited an effectual photodegradation of methylene blue (MB) under UV illumination, with a chemical reaction constant of 2.93 × 10−3 min−1. In this present work, we demonstrated that the CA value of the ZnO films not only caused a change from a hydrophobic to hydrophilic status, accompanied by a change in grain size combined with internal stress, but also, induced by the UV light illumination, was combined with photocatalytic activity simultaneously. On the other hand, an enhanced surface plasmonic resonance was observed, which was due to couple oscillations between the electrons and photons and was generated from the interface by using a flat, continuous Pt capping nanolayer. This designed structure may also be considered as a Pt electrode pattern onto ZnO (metal Pt/ceramic ZnO) for multifunctional, heterostructured sensors and devices in the near future.

Modulation of carrier transport in bipolar response BDD/SnO2 p+-n heterojunction UV photodetectors

A unique band-to-band tunneling (BTBT) phenomenon has been discovered in heavily boron-doped diamond (BDD)/SnO2 p+-n heterojunctions. This phenomenon can be modulated by varying the bias voltage, changing the thickness of the SnO2 film, and adjusting the power density of incident UV light. The near-broken-gap band alignment of the BDD/SnO2 heterojunction and the existence of electrons in degenerate states in the valence band of BDD are the key to achieving BTBT. Moreover, BDD/SnO2 p+-n heterojunction UV photodetectors (PDs) prepared by radio-frequency magnetron sputtering exhibit a binary photoresponse, large open-circuit voltage (Voc-l), and high photo/dark current ratio (Ip/Id). Those behaviors can be produced through periodic on/off UV light irradiation and by changing tunneling, drift, and thermionic emission currents. Our work, which is the first to achieve a binary photoresponse by modulating BTBT in BDD/SnO2 heterojunctions, demonstrates the feasibility of extending BTBT theory to logical optoelectronic devices.