Simultaneous RF Magnetron Sputtering Research Articles

Analysis of optical, structural, and morphological properties of a Ti-doped α-Fe2O3 thin film produced through RF and DC magnetron Co-sputtering

In this study, a Titanium (Ti) doped α-Fe2O3 (hematite) thin layer was synthesized onto a glass substrate, employing the simultaneous DC and RF magnetron sputtering method. The investigation focused on examining specific physical properties of the film. The optical, structural, morphological, and elemental features of the resulting Ti-doped α-Fe2O3 thin film were characterized using different characterization techniques. The XRD studies indicated a rhombohedral crystal structure in the studied thin film. The calculation of the Eg value for the thin film, based on absorption measurements, resulted in a value of 2.19 eV. Raman peaks were identified within the range of 218 cm−1 to 1300 cm−1. According to SEM images, the thin film exhibited a uniform surface morphology across the substrate. AFM images revealed a low root mean square (RMS) roughness value, indicating a smooth Ti:Fe2O3 thin film surface.

Effect of swift heavy ion irradiation on the resistive random access memory performance of sputter deposited zinc rich zinc oxide thin films

Resistive Random-Access Memory (RRAM) devices are synthesized by sandwiching (i) ZnO thin film and (ii) Zn-rich ZnO thin film between top and bottom conducting electrodes consisting of Au thin layer and ITO substrate respectively. DC Sputtering was used to create the metal contact at the top of the device, while simultaneous RF and DC magnetron sputtering was used to form the ZnO and metal-rich oxide layer-based devices. The RRAM device was irradiated with 100 MeV Ag at a fluence of 1013 ions/cm2. The I-V characteristics of pristine and irradiated Au/ZnO/ITO and Au/Zn rich ZnO/ITO were measured using a semiconductor device analyser B1500. The thickness, stoichiometry, and crystallinity of zinc oxide thin films were determined using Rutherford Back Scattering, X-ray diffraction and Raman Spectroscopy. The present work shows that the performance of RRAM devices both in the ZnO and Zn rich ZnO significantly improves by ion irradiation.

Realization of electrolyte interface effect on Bi2Te3 implanted flake-like ZnO thin films for understanding the highly stable PEC water splitting under simulated solar light and visible light

This study aimed to rationally design the novel Bi2Te3 implanted ZnO (Bi2Te3@ZnO) thin films using simultaneous RF and DC magnetron sputtering technique. Herein, we explored the electrolyte interface effect (0.1 M of KOH, KCl, Na2SO3 and Na2SO4) on ZnO and Bi2Te3@ZnO towards highly stable PEC water splitting activity for the first time. Specifically, morphological evolution and electrolyte ion diffusion properties play a crucial role in realizing the prolonged charge carrier lifetime. Moreover, Bi2Te3@ZnO is highlighted with unique nanocone-shaped morphology compared to flake-like ZnO. Also, constructive interfacial interaction was observed between Bi2Te3 and ZnO. As a result, Bi2Te3@ZnO demonstrated superior and highly stable photocurrents in the KOH electrolyte compared to KCl, Na2SO3 and Na2SO4 electrolytes. Precisely, Bi2Te3@ZnO triumphed highly stable photocurrents about 7.93 × 10–4 A cm−2 compared to ZnO (6.02 × 10–4) at +0.4 V under solar light in KOH electrolyte. Accordingly, Bi2Te3@ZnO achieved remarkable photoconversion efficiency (η) about 0.65 %, which is enabled by the strengthened intimate interaction between Bi2Te3 and ZnO. Furthermore, we compared the PEC activity under visible light (UV cut-off solar light). These results highlighted that the photoconversion efficiency difference between Bi2Te3@ZnO and ZnO (about 4 times) under visible light is relatively higher than solar light (1.3 times) in KOH. Thus, we proposed different charge carrier generation mechanisms of Bi2Te3@ZnO under solar and visible light. Therefore, intimate interfacial interaction, surface modification, ion diffusion and photoelectrode-electrolyte interaction are key parameters to enhance the PEC activity. Overall, rational design of the transition metal oxide/thermoelectric material interface using Bi2Te3@ZnO composite paves a new path towards highly stable photoanode during PEC water splitting activity in the KOH electrolyte environment.

Formation of a phase pure kesterite CZTSe thin films using multisource hybrid physical vapour deposition

Copper Zinc Tin Selenide (CZTSe) absorber films were obtained by growing CZT films with simultaneous RF and DC magnetron sputtering followed by thermal evaporation of Selenium. The deposition of CZTSe films was performed with different sputter powers with in-situ and post annealing of the deposited films at 400 °C in order to get uniformity and phase purity. Detailed GIXRD analysis concluded that a phase pure CZTSe film was obtained for in-situ annealed sample with Cu-Sn deposited through RF sputter power of 250W and Zn deposited through pulsed DC power of 200W. In conclusion from Raman scattering measurements, phase pure Raman active A mode of Kesterite CZTSe was observed for the same sample. Compositional analysis by EDS and XPS clearly showed that the CZTSe films are having Cu poor and Zn rich composition, favoring shallow Cu-vacancy which is highly desirable as p-type absorber layers for solar cells. The optical bandgaps (Eg) of the films calculated using Tauc plots were within the reported bandgap value of 1.0–1.35eV. The present deposition approach using hybrid PVD tool helps to control individual fluxes (Cu-Sn, Zn, Se), more precisely without the need of extra selenization step, leading to one step reduction in production process.

Insight into anions and cations effect on charge carrier generation and transportation of flake-like Co-doped ZnO thin films for stable PEC water splitting activity

Developing a stable interface interaction between photoelectrode and electrolyte is crucial for achieving superior photoelectrochemical (PEC) water splitting activity. In this aspect, the contribution of anions and cations present in the electrolyte play a decisive role during its interaction with the solvent and surface functional groups on the developed photoelectrode, which greatly determine the charge carrier generation and transportation. Herein, we developed the flake-like Co (1.7 at.%)-doped ZnO (Co-ZnO) thin films by employing simultaneous RF and DC magnetron sputtering, which were post annealed at 250 °C for 2 h. The developed films were used to demonstrate the PEC activity under different aqueous electrolytes (KCl, KOH, NaOH, Na2SO3 and Na2SO4). Most importantly, owing to the promising flake-like features of Co-ZnO, efficient electrode-electrolyte interface interaction has been achieved for stable and improved PEC activity. In turn, detailed PEC activity in KCl, KOH and NaOH electrolytes demonstrated that K+ cations and OH− anions in KOH greatly influenced the photocurrents than KCl (Cl−) and NaOH (Na+) due to the high ionic conductive and diffusion properties. On the other hand, SO32− (Na2SO3) anions tailor the charge carrier generation by the advantage of hole scavenging activity compared to SO42− (Na2SO4). Comprehensively, our results provide new insight into the selection of aqueous electrolyte to improve the PEC water splitting activity through adopting the ionic conductivity and constructive interaction with photoelectrode.

Highly supportive hydrogen peroxide as a hole scavenger to improve the visible light water splitting activity of flake-like Co-doped ZnO thin films

In the present work, we explored the hole scavenging activity of hydrogen peroxide (H2O2) on flake-like Co-doped ZnO thin films to improve the visible light photoelectrochemical (PEC) water splitting activity. To address this phenomenon, we developed promising Co (0, 0.8, 1.7 and 2.2 at.%)-doped ZnO thin films by simultaneous RF and DC magnetron sputtering. First, precise control on Co doping level in the ZnO host lattice has been demonstrated to facilitate superior water splitting activity through the strategic surface transformation. Accordingly, Co doping concentration significantly modulated the structural properties of ZnO (0 0 2). From FESEM analysis, clear morphological changes were observed from granular (Co-0 at.%) to flake-like (Co-1.7 at.%). Also, AFM analysis provided insights into surface roughness (7.0 nm) and maximum height of roughness (35 nm) of Co (1.7 at.%)-ZnO thin films. Furthermore, TEM analysis highlighted the crystalline changes on Co (1.7 at.%)-ZnO thin films. Thus, Co (1.7 at.%)-ZnO exhibited a reduced band gap (3.07 eV). Notably, flake-like Co (1.7 at.%)-ZnO thin films validated with prominent hydrophilicity. As a result, the morphology of Co (1.7 at.%)-ZnO facilitated superior visible light PEC activity than others. Second, to accelerate the PEC activity, hole scavenging mechanism has been proposed by the addition of H2O2 into the KOH. Our results show how the HO2* radicals contributed to suppressing the hole accumulation, recombination and cathodic currents at the interface of Co-ZnO/electrolyte. Overall, we believe that the proposed hole scavenger strategy provides new insight into improved visible light PEC water splitting activity on flake-like Co-ZnO thin films.

Wettability and optical properties of SnO–SnO2–Sb2O3 thin films deposited by simultaneous RF and DC magnetron sputtering

The SnO–SnO2–Sb2O3 films were deposited by simultaneous RF and DC magnetron sputtering. Increasing the ratio of O2/Ar pressure raised the intensity of the (311) peak of cubic Sb2O3 and the (200) peak of tetragonal SnO2, but clearly reduced the intensity of the (101) peak of tetragonal SnO2. According to visible-photoluminescence analyses, the blue shift of the PL peak can be attributed to the combination of smaller grains and higher compressive strain in the SnO–SnO2–Sb2O3 films. The nonlinear refractive indices of SnO–SnO2–Sb2O3 films deposited in a pure Ar or a mixed Ar–O2 atmosphere were measured by Moiré deflectometry, and were of the order of 10−8 cm2 W−1. At a higher ratio of O2/Ar pressure, a transparent SnO–SnO2–Sb2O3 film exhibited a lower surface roughness, better hydrophilicity, a higher linear refractive index and a lower extinction coefficient.

Enhanced photoluminescence properties of Cu-doped ZnO thin films deposited by simultaneous RF and DC magnetron sputtering

Copper (Cu)-doped ZnO thin films were grown on unheated glass substrates at various doping concentrations of Cu (0, 5.1, 6.2 and 7.5at%) by simultaneous RF and DC magnetron sputtering technique. The influence of Cu atomic concentration on structural, electrical and optical properties of ZnO films was discussed in detail. Elemental composition from EDAX analysis confirmed the presence of Cu as a doping material in ZnO host lattice. XRD patterns show that the films were polycrystalline in nature with (002) as a predominant reflection of ZnO exhibited hexagonal wurtzite structure toward c-axis. From AFM analysis, films displayed needle-like shaped grains throughout the substrate surface. The electrical resistivity was found to be increased with increase of Cu content from 0 to 7.5at%. Films have shown an average optical transmittance about 80% in the visible region and decreased optical band gap values from 3.2 to 3.01eV with increasing of Cu doping content from 0 to 7.5at% respectively. Furthermore, remarkably enhanced photoluminescence (PL) properties have been observed with prominent violet emission band corresponding to 3.06eV (405nm) in the visible region through the increase of Cu doping content in ZnO host lattice.

Effects of the ratio of O2/Ar pressure on wettability and optical properties of HfO2 films before and after doping with Al

HfO2 films were doped with Al (HfO2:Al) by simultaneous RF magnetron sputtering of HfO2 and DC magnetron sputtering of Al. This method is characterized by its ability to independently control the Al content. According to XRD and XPS analyses, the HfO2:Al film had a structure similar to that of HfO2 film, and most of the Al atoms were not in the HfO2 crystalline. A small amount of Al3+ dopant could transform the hydrophobicity of HfO2 films into hydrophilicity. Moreover, the hydrophilicity of the HfO2:Al films improved as the ratio of O2/Ar pressure increased. The nonlinear refractive indices of HfO2 and HfO2:Al films deposited in a pure Ar or a mixed Ar–O2 atmosphere were measured by Moiré deflectometry, and were of the order of 10–8 cm2 W–1. A lower surface roughness, higher optical transmission in the UV–vis–NIR region, and higher linear refractive index were obtained at a higher ratio of O2/Ar pressure.

Study of Cu-based Al-doped ZnO multilayer thin films with different annealing conditions

AZO/Cu/AZO multilayer thin films produced under different annealing conditions are studied in this paper, to examine the effects of atmosphere and annealing temperature on their optical and electrical properties. The multilayer thin films are prepared by simultaneous RF magnetron sputtering (for AZO) and DC magnetron sputtering (for Cu). The thin films were annealed in a vacuum or an atmosphere of oxygen at temperatures ranging from 100 to 400°C in steps of 100°C for 3min. High-quality multilayer films (at Cu layer thickness of 15nm) with resistivity of 1.99×10−5Ω-cm and maximum optical transmittance of 76.23% were obtained at 400°C annealing temperature in a vacuum. These results show the films to be good candidates for use as high quality electrodes in various displays applications.

Effect of ion beam assistance on Cu- doped ZnO thin films deposited by simultaneous RF and DC magnetron sputtering

Ion-beam-assisted Cu-doped ZnO (CZO) thin films were deposited on unheated glass substrates by simultaneous RF and DC magnetron sputtering of zinc oxide (ZnO) and copper (Cu) respectively. The as-deposited films were subjected to thermal annealing at 200°C for one hour. The effects of ion-beam-assistance and thermal annealing on the structural, morphological and optical properties of CZO films have been systematically studied. From XRD studies, it was found that the deposited films were polycrystalline in nature with (002) as a predominant characteristic orientation of ZnO crystallized in hexagonal wurtzite structure along the c-axis perpendicular to the substrate surface. Ion-beam-assistance on CZO films significantly influenced the predominant (002) reflection. Additional diffusion energy gained by the adatoms during film growth enhances the Cu concentration in ZnO host lattice, leads to disruption of (002) reflection. In addition, the surface morphology of deposited films displayed the presence of hexagonal granular-shaped grains vertical to the substrate. Furthermore, we observed that optical transmittance of the as-deposited and annealed films decreased with effect of ion-beam-assistance. Consequently, the optical absorption edge gradually shifted towards longer wavelength side, it resulted to decrease of band gap energy.

Fabrication and characterization of ZnO/AI/ZnO multilayers by simultaneous DC and RF magnetron sputtering

The present investigation reports the fabrication and characterization of multilayered transparent electrodes by simultaneous DC and RF magnetron sputtering on glass substrates. The multilayer structure consists of three layers (ZnO/Al/ZnO). The influence of Al layer thickness on the electrical and optical properties was investigated. Optimum thickness of Al was determined for high transmittance and good electrical conductivity. High quality films having resistance as low as 25 Ω/sq with optical transmittance upto 65% were obtained at room temperature.

Effects of substrate temperature on properties of HfO2, HfO2:Al and HfO2:W films

The HfO2 films were doped with Al (HfO2:Al) or W (HfO2:W) by simultaneous RF magnetron sputtering of HfO2 and DC magnetron sputtering of Al or W. According to XRD analysis, the monoclinic HfO2 film and a strong 1−11 preferential orientation were obtained as the substrate temperature increased to 500°C. After doping with Al, a (300) preferential orientation in Al2O3 and the coexistence of monoclinic HfO2, orthorhombic HfO2 and Al2O3 were obtained at the substrate temperature of 500°C. By increasing the substrate temperature, the coexistence of monoclinic HfO2 and tetragonal W5O14 was obtained in the HfO2:W film. Doping with Al or W could change the hydrophobicity of HfO2 films into the hydrophilicity. The HfO2:W films exhibited better hydrophilicity and lower average visible light transmission at higher substrate temperature. The hydrophilic HfO2:Al film showed higher average visible light transmission and higher linear refractive index at lower substrate temperature, favoring optical applications.

The optical properties of hydrophilic Ti-doped Al2O3 films

Ti-doped Al2O3 (Al2O3:Ti) films were prepared by the simultaneous RF magnetron sputtering of Al2O3 and DC magnetron sputtering of Ti. The structure of the Al2O3:Ti film corresponded to Al2O3. Reducing RF power caused the formation of thinner fibers of Al2O3:Ti in the film, favoring the hydrophilicity and increasing the optical energy gap of the deposited film. When a thicker Al2O3:Ti film was deposited at a higher RF power, it contained thicker fibers, and had a lower surface roughness, higher visible transmission and a higher linear refractive index. The Al/Ti atomic ratio significantly affected the hydrophilicity and optical properties of Al2O3:Ti films.

AZO/Au/AZO tri-layer thin films for the very low resistivity transparent electrode applications

Abstract Aluminum-doped ZnO (AZO)/gold/AZO tri-layer structures with very low resistivity and high transmittance are prepared by simultaneous RF magnetron sputtering (for AZO) and ion sputtering (for Au). The properties of the tri-layer films are investigated at different Au layer thicknesses (5–20 nm). The effects of Au layer thickness and the role of Au on the transmission properties of the tri-layer films were investigated. The very low resistivity of 1.01 × 10−5 Ω cm, mobility of 27.665 cm2 V−1 s−1, and carrier concentration of 4.563 × 1022 cm−3 were obtained at an Au layer thickness of 20 nm. The peak transmittance of 86.18% at 650-nm wavelength was obtained at an Au layer thickness of 8 nm. These results show the films to be a good candidate for high-quality electrode scheme in various display applications.

Properties of Ti-doped Al2O3 thin films deposited by simultaneous RF and DC magnetron sputtering

The Ti-doped Al2O3 (Al2O3:Ti) films were prepared by simultaneous RF magnetron sputtering of Al2O3 and DC magnetron sputtering of Ti. The advantage of this method is that the Ti content could be independently controlled. Decreasing the DC power or increasing the ratio of O2 to Ar pressure made the Al2O3:Ti film be more stoichiometric. By decreasing the DC power or increasing the ratio of O2 to Ar pressure, the hydrophilic Al2O3:Ti film exhibited lower surface roughness, higher average visible transmission, higher linear refractive index and lower stress-optical coefficient.

Effects of Annealling Treatment on the Properties of TiO<sub>2</sub>/ZnO Thin Film Prepared by Simultaneous RF-Magnetron Sputtering

In this work, TiO2/ZnO nanocomposite films were prepared by simultaneous RF-magnetron sputtering of ZnO and TiO2targets. The influences of annealing temperature on the properties of the TiO2/ZnO films were investigated. The crystal structure of the deposited TiO2/ZnO films was hexagonal wurtzite at (002) and (101) peaks and the films were highly oriented along the c-axis perpendicular to the substrate. The photoluminescence (PL) spectrum reveals the appearance of two emission peaks from the deposited film that are centred at 384 and 591 nm. The structural, electrical, and optical properties of TiO2/ZnO films were strongly dependent on the annealing temperature. With increasing of the annealing temperature, the optical properties (i.e., UV, transmittance, energy band-gap and crystalline quality) were also improved. However, when the annealing is relatively high (≥ 500° C), the intensity of the optical properties and crystalline quality slightly decreases. The annealing temperature of (≥ 500° C) becoming the threshold temperature limits for the TiO2/ZnO film. The results obtained herein suggest that selecting the appropriate annealing temperature become a key factor for tuning the most desired properties from the as-prepared TiO2/ZnO thin films.

Properties of heavily W-doped TiO2 films deposited on Al2O3-deposited glass by simultaneous rf and dc magnetron sputtering

Abstract TiO 2 films were heavily doped with W (TiO 2 :W) by simultaneous rf magnetron sputtering of TiO 2 , and dc magnetron sputtering of W. The advantage of this method is that the W content could be changed in a wide range. The coexistence of TiO 2 , WO 3 and TiWO 5 in the TiO 2 :W film was detected by XPS analysis. Besides, tungsten in TiO 2 :W film on the bare glass may form mixed valence of W 0+ and W 6+ . Electrical conductivity was primarily due to the contribution of oxygen vacancies and W donors (W Ti ). When the film thickness increased, the TiO 2 :W film showed higher carrier concentration and higher mobility. Furthermore, the resistivity and the transmission decreased obviously with film thickness. On comparing with the TiO 2 :W film deposited on the bare glass, the TiO 2 :W film on the Al 2 O 3 -deposited glass exhibited lower surface roughness, lower resistivity, higher optical energy gap, higher optical transmission, and lower stress-optical coefficient.

Structure and physical properties of W-doped HfO2 thin films deposited by simultaneous RF and DC magnetron sputtering

The W-doped HfO2 (HfO2:W) films were prepared by simultaneous RF magnetron sputtering of HfO2 and DC magnetron sputtering of W. The advantage of this method is that the W content could be independently controlled. The coexistence of W compounds and HfO2 was observed by XPS. Increasing the ratio of O2 to Ar pressure made the HfO2:W film be more stoichiometric. A control of the presence of HfWO5 is a way to enhance strongly the hydrophilicity of HfO2:W film. By decreasing the W content or increasing the ratio of O2 to Ar pressure, HfO2:W film exhibited lower surface roughness, higher visible transmission, a higher linear refractive index and a lower stress-optical coefficient.

The optical properties of hydrophilic Hf-doped HfO2 nanoceramic films

The Hf-doped HfO 2 (HfO 2 :Hf) nanoceramic films were deposited by simultaneous rf magnetron sputtering of HfO 2 and dc magnetron sputtering of Hf. By doping with Hf, the lowest oxidation state of Hf (Hf 0+ ) presented preferentially and changed the hydrophobicity of HfO 2 film into hydrophilicity. On comparing with the HfO 2 film, the optical transmission of HfO 2 :Hf film was higher and strongly increased with pressure, especially in the ultraviolet region and near infrared region. At higher pressure, HfO 2 :Hf film exhibited better hydrophilicity, higher linear refractive index and lower stress-optical coefficient.