Radio Frequency Magnetron Sputtering Deposition Research Articles

Investigation of pulsed ultraviolet laser annealing of Sb/SnO2 thin films on the structural, optical and electrical properties

Sb/SnO2 bi-layer films were prepared using ion beam sputtering deposition (IBSD) and radio frequency (RF) magnetron sputtering deposition. The optimal parameters of SnO2 thin films were found to be dependent on the processing conditions of vacuum pressure and flow ratio of O2/(O2+Ar). The as deposited bi-layer films were treated by ex situ pulsed ultraviolet laser beam at 355nm for the assistance of Sb-ion with SnO2 interface. This paper takes a closer look at the characteristics of the laser irradiation effect of Sb/SnO2 bi-layer films on the optical and electrical behavior and the interface microstructure of Sb/SnO2 by high resolution transmission electron microscopy (HR-TEM). After UV pulse laser irradiation of bi-layer films, crystalline Sb between amorphous Sb and SnO2 nanocrystalline thin films was observed.

Effect of growth temperature on characteristics of Cr-doped ZnO nanorods by magnetron sputtering

Cr-doped ZnO nanostructures, in well-aligned Zn0.92Cr0.06O nanorods array, were synthesized by radio frequency (RF) magnetron sputtering deposition at different temperatures. The effects of growth temperature on the structure and optical properties of Zn0.92Cr0.06O nanorods were investigated in terms of scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS) and spectrophotometer. With increase the growth temperature, Zn0.94Cr0.06O nanorods have a strong improved crystalline quality. High growth temperature enhances the build-in electric field in the depletion region in the grain of the nanorods, which trap free carriers from the bulk of the grains. XPS results shows that Cr3+ ions substitute Zn2+ ions, and no secondary phases in the sample are found, meanwhile the oxygen vacancies decrease with increasing growth temperature. The high growth temperature causes a significant increase in optical transmittance of the Zn0.92Cr0.06O nanorods, which can be attributed to the weakening of scattering and absorption of light because of the increase of grain size. The red shift of the optical band gap can be mostly likely related to the Burstein–Moss effect.

Development of dye-sensitized solar cells based on visible-light-responsive TiO2 thin films with a unique columnar structure

A visible-light-responsive TiO2 thin film (Vis-TiO2), possessing a unique columnar structure oriented perpendicular to the substrate, has been prepared by using a radio-frequency magnetron sputtering deposition method. The unique TiO2 thin film was used as a key component of N719 dye-sensitized solar cells (DSSCs). The rough morphology caused by the columnar structure leads to enhanced photovoltaic performances of these DSSCs as a consequence of increased amounts of adsorbed dyes and facilitated diffusion of the electrolyte into Vis-TiO2 film. Additionally, photovoltaic performances of the DSSCs were found to depend strongly on the thickness of the Vis-TiO2 film, which can be readily controlled by adjusting the sputtering time conducted for deposition. Consequently, a solar-to-electric energy conversion efficiency of 2.6 % under AM 1.5 illumination was observed for an optimally performing DSSC that has a Vis-TiO2 film thickness of 6.9 μm, prepared by employing a sputtering time of 700 min.

Effect of the sputtering parameters on the physical properties and photocatalytic reactivity of TiO2 thin films prepared by an RF magnetron sputtering deposition method

Visible light-responsive TiO2 (Vis-TiO2) thin films were successfully developed by applying a radio-frequency magnetron sputtering deposition method by controlling various sputtering parameters such as the substrate temperature, Ar gas pressure, and the target-to-substrate distance. UV–Vis, XRD and SEM investigations revealed that optical property, the crystal structure, and photocatalytic activity of Vis-TiO2 are strongly affected by the sputtering parameters during the deposition step. Vis-TiO2 was found to act as an efficient photocatalyst for the H2 and O2 evolution from water under visible light irradiation (λ ≥ 420 nm). SIMS investigations have revealed that a slight decrease in the O/Ti ratio of the TiO2 thin films plays an important role in the modification of the electronic properties of Vis-TiO2 thin films, enabling them to absorb visible light.

Antibacterial property of CuCrO2 thin films prepared by RF magnetron sputtering deposition

The present study investigates the antibacterial properties of CuCrO2 thin film surfaces against Escherichia coli (E. coli) bacteria. Single-phase delafossite type copper-chromium oxide (CuCrO2) thin films were prepared on glass substrate by radio-frequency (RF) magnetron sputtering, followed by two-step post-deposition annealing at 400 °C with 5% forming gas and at 600 °C in a nitrogen atmosphere. The structure of the CuCrO2 thin films was confirmed by X-ray diffraction. The transmittance properties were measured by a UV–Vis spectrometer. The ISO 22196 method was utilized to evaluate the colony forming unit (CFU) of E. coli on the CuCrO2 surface after several hours. The experimental results find the CuCrO2 surface to exhibit superior antibacterial performance and an optical transparency of >70% in the visible region with a thickness of 100 nm. A novel transparent antibacterial coating has been demonstrated in the present study.

Bulk Heterojunction Formation between Indium Tin Oxide Nanorods and CuInS2 Nanoparticles for Inorganic Thin Film Solar Cell Applications

In this study, we developed a novel inorganic thin film solar cell configuration in which bulk heterojunction was formed between indium tin oxide (ITO) nanorods and CuInS(2) (CIS). Specifically, ITO nanorods were first synthesized by the radio frequency magnetron sputtering deposition method followed by deposition of a dense TiO(2) layer and CdS buffer layer using atomic layer deposition and chemical bath deposition method, respectively. The spatial region between the nanorods was then filled with CIS nanoparticle ink, which was presynthesized using the colloidal synthetic method. We observed that complete gap filling was achieved to form bulk heterojunction between the inorganic phases. As a proof-of-concept, solar cell devices were fabricated by depositing an Au electrode on top of the CIS layer, which exhibited the best photovoltaic response with a V(oc), J(sc), FF, and efficiency of 0.287 V, 9.63 mA/cm(2), 0.364, and 1.01%, respectively.

Workfunction tuning of zinc oxide films by argon sputtering and oxygen plasma: an experimental and computational study

Zinc oxide (ZnO) films were grown by radio frequency magnetron sputter deposition and the changes to its surface composition and workfunction induced by argon sputter cleaning and oxygen plasma treatments were characterized using x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and density functional theory modelling. Compared with a workfunction of 3.74 eV for the as-deposited ZnO films, a workfunction of 3.95 eV was obtained after Ar sputter cleaning and 4.21 eV after exposure to oxygen plasma. The data indicate that oxygen plasma treatment leads to a more negative ZnO surface. The dipole induced by this charge redistribution reinforces the original surface dipole, which results in an increase in the surface dipole moment and an increase in workfunction. The reverse is true for hydrocarbon contamination of ZnO surfaces. Excellent qualitative agreement between the experimental results and computational modelling was obtained. The results suggest that specific surface functionalization may be a viable method of controlling the workfunction of ZnO for use as the transparent conducting oxide in optoelectronic applications such as solar cells and organic light-emitting diodes.

Magnetron Sputtering Preparation of Nitrogen-Incorporated Lithium–Aluminum–Titanium Phosphate Based Thin Film Electrolytes for All-Solid-State Lithium Ion Batteries

We report for the first time a new lithium ion conducting Li–Al–Ti–P–O–N thin film solid electrolyte for all-solid-state lithium ion batteries. It was prepared by radio frequency (RF) magnetron sputtering deposition using a NASICON structural Li–Al–Ti–P–O target in a N2 atmosphere at various temperatures. XRD and SEM test results showed that the thin film was composed of an amorphous structure and that its surface was smooth, dense, and homogeneous. FTIR and XPS analyses indicated that nitrogen atoms were actually incorporated into the Li–Al–Ti–P–O matrix framework. The substitution of nitrogen for oxygen in the thin film created more abundant cross-linking structures and decreased the electrostatic energy, which favored the higher mobility of lithium ions. A high Li ionic conductivity of 1.22 × 10–6 S/cm was obtained for the thin film deposited at room temperature. Moreover, the higher value of 1.22 × 10–5 S/cm for the thin film deposited at 500 °C indicated that some crystallites in the amorphous film m...

Plasma-etching fabrication and properties of black silicon by using sputtered silver nanoparticles as micromasks

A nanohill structure has been fabricated on a silicon surface via a micromask formed by a radio-frequency magnetron sputtering deposition of silver nanoparticles and a following dry etching under SF6 plasma. The proposed technique does not rely on oxygen gas to eliminate the damages from oxygen plasma and to increase the lifetime of the silicon crystal. The experiments indicate that the morphology and particle size distribution of silver nanoparticles determine the reflectivity of the textured silicon wafer. Interestingly, the nanohill structure exhibits a stronger light confinement ability than the columnar one, leading to a lower reflectivity. A longer minority carrier lifetime is obtained in such nanohill structures with a lower defect concentration on the surface. This work provides a pathway to fabricating black silicon of excellent light confinement structure, which may have potential for applications in some localized surface plasmons-relevant areas.

Photocatalytic oxidation of 2-propanol under visible light irradiation on TiO2 thin films prepared by an RF magnetron sputtering deposition method

Visible light-responsive TiO2 (Vis-TiO2) thin films able to absorb UV and visible light in wavelength regions of 250-600 nm were successfully developed by applying a radio-frequency magnetron sputtering deposition method. These Vis- TiO2 thin films exhibited high activity for the photocatalytic oxidation of 2-propanol diluted in water even under visible light irradiation (k C 450 nm). The photocata- lytic activity of Vis-TiO2 thin films was dramatically enhanced by the deposition of Pt particles on the surface. Secondary ion mass spectrometry measurements revealed that Pt particles are distributed from the top surface to the deep bulk of Vis- TiO2 thin films with a columnar structure. The unique columnar structure of Vis- TiO2 thin films plays an important role in the high photocatalytic performance.

Structural and Electrical Properties of Mg–Si Thin Films Fabricated by Radio-Frequency Magnetron Sputtering Deposition

ABSTRACTMg–Si thin films were fabricated on glass, Si(100), Si(111), and polycrystalline Al2O3 substrates by radio-frequency (RF) magnetron sputtering deposition using an elemental composite target composed of Si chips on a Mg disk. The effect of deposition conditions such as the composition ratio of Mg/Si in the target area, substrate temperature, and the type of substrate on the thin film deposition was investigated. By controlling the deposition conditions, pure-phase Mg2Si polycrystalline films were successfully fabricated at room temperature. The crystalline orientation of the films was strongly influenced by the Mg/Si elemental composition ratio in the targets as well as by the surface roughness and porosity of the substrate. The electron concentration and mobility of nondoped Mg2Si films were 2.2 × 1016 cm-3 and 2.0 cm2/Vs, respectively. The electron concentration of Mg2Si films was drastically increased by impurity doping with Al and Bi.

High efficiency dye-sensitized solar cells exploiting sponge-like ZnO nanostructures

Sponge-like nanostructured ZnO layers were successfully employed as photoanodes for the fabrication of highly efficient dye-sensitized solar cells. The sponge-like ZnO layers were obtained by room temperature radio-frequency magnetron sputtering deposition of metallic zinc, followed by thermal oxidation treatment in an ambient atmosphere. The porous films show a 3D branched nanomorphology, with a feature similar to natural coral. The morphological and optical properties of these layers were studied through field emission scanning electron microscopy, specific surface area measurements, ultraviolet-visible transmittance and absorption spectroscopy. The sponge-like ZnO film presents a high density of branches, with a relatively high specific surface area value, and fine optical transmittance. The morphology of the porous structure provides a high number of adsorption sites for the anchoring of sensitizer molecules, making it suitable for the fabrication of ZnO-based photoanodes for dye-sensitized solar cells. The light harvesting performance of the sensitized semiconductor was evaluated by current density vs. voltage measurements, incident photon-to-electron conversion efficiency, open circuit voltage decay and impedance spectroscopy. The modelling of the electrical characteristics evidences a higher electron lifetime and a longer charge diffusion length, if compared to standard TiO(2) nanoparticle based photoanodes. For ZnO films with a thickness up to 18 μm, a photoconversion efficiency as high as 6.67% and a maximum value of the incident photon-to-electron collection efficiency equal to 87% at 530 nm were demonstrated.

Preparing transparent conductive Sn/Sb–O2 − x thin films by annealing bi-layer Sb/SnO2 with pulse UV laser

Sb/SnO2 bi-layer films were prepared on glass substrates using ion beam sputtering deposition (IBSD) and radio frequency (RF) magnetron sputtering deposition technology. The as-deposited bi-layer films were irradiated with a pulsed ultraviolet (UV) laser beam at 355nm for the characteristic modulation which is expected to receive interest in the subtle transition. The effect of laser irradiation on the optical and electrical behavior and the chemical state of the films was investigated using X-ray photoelectron spectroscopy (XPS). The conductivity of Sb/SnO2 after laser irradiation increased in comparison with that of SnO2 and as-deposited Sb/SnO2 thin films. The optical transmittance of laser irradiated Sb/SnO2 increased from 41% to 47%.

Resistive switching characteristics of thin NiO film based flexible nonvolatile memory devices

Flexible resistive switching device consisting of thin NiO film sandwiched between a flexible Cu foil substrate and Ti top electrode is proposed in this work. The Ti/NiO/Cu structure was fabricated by radio frequency magnetron sputtering deposition of a NiO film on the flexible Cu foil substrate. The fabricated device showed stable bipolar resistive switching behavior and its performance was not degraded upon different bending states. The Ti/NiO/Cu flexible device presented in our work has potential applications in the field of resistive switching random access memory (RRAM) devices.

Thermochromic properties and low emissivity of ZnO:Al/VO 2 double-layered films with a lowered phase transition temperature

We studied the optical and semiconductor–metal (S–M) transition properties of ZnO:Al/VO 2/substrate double-layered films that consisted of a ZnO:Al top layer and a VO 2 bottom layer. ZnO:Al and VO 2 films were grown on fused silica substrates by radio frequency magnetron sputtering and polymer-assisted deposition, respectively. The ZnO:Al/VO 2/substrate films displayed low emissivity (0.31–0.32) with integrated luminous transmittance ( T lum >46%) and thermochromic properties (Δ T sol >4.1%). The low emissivity and thermochromic properties were independently introduced by the transparent conductive ZnO:Al layer and the VO 2 layer. In addition, the S–M transition temperatures for VO 2 shifted to lower temperatures after the ZnO:Al deposition process, which was due to the formation of surface nonstoichiometry—oxygen deficiency that was induced by the ZnO:Al deposition process.

Sputtering and Pulsed Laser Deposition for Near- and Mid-Infrared Applications: A Comparative Study of Ge25Sb10S65 and Ge25Sb10Se65 Amorphous Thin Films

The deposition of Ge25Sb10S65 and Ge25Sb10Se65 amorphous chalcogenide thin films was performed by radio-frequency magnetron sputtering and pulsed laser deposition technique. The deposited layers were characterized by studying their morphology, topography, chemical composition, structure, and optical functions permitting a direct comparison of two deposition methods for obtaining attractive amorphous chalcogenide films. Reactive ion etching was then used to pattern rib/ridge waveguides in sulfide and selenide films with low surface roughness, vertical sidewalls, and reasonable etching rate. Optical losses of fabricated waveguides were measured at 1550 nm with values better than 1 dB/cm obtained for sulfide/selenide films deposited by both techniques.

Mechanical properties and antibacterial activity of copper doped diamond-like carbon films

A hydrogenated diamond-like carbon (a-C:H) with a copper dopant (Cu/a-C:H) was deposited on glass substrates using a combined radio-frequency plasma and magnetron sputtering deposition process under various Ar/CH 4 gas mixtures. The effects of the Cu content on the structure and properties of the a-C:H matrix were investigated using X-ray diffraction (XRD), Raman transmission electron microscopy, high-resolution transmission electron microscopy (TEM), and nano-indentation. The bacterial activity of a Cu/a-C:H film was evaluated with Escherichia coli ( E. coli). TEM images and XRD spectra demonstrated that composite films containing copper nanoparticles embedded in the a-C:H were deposited on the glass substrates. The Raman spectra showed the structure of a-C:H film was substantially changed by the incorporation of Cu. The Cu/a-C:H films offered superior antibacterial activity against E. coli indicating that they could be suitable for surface coatings in cardiovascular applications.

Sputtered Pt loadings of membrane electrode assemblies in proton exchange membrane fuel cells

SUMMARY The fabrication of electrodes use in proton exchange membrane fuel cells (PEMFCs) by Pt sputter deposition has great potential to increase Pt utilization and reduce Pt loading without loss of cell performance. A radio frequency (RF) magnetron sputter deposition process (RF power = 100 W and argon pressure = 10−3 Torr) was adopted to prepare Pt catalyst layers of PEMFC electrodes. The effects of cathode Pt and Nafion loadings on membrane electrode assembly (MEA)/cell performance were investigated using cell polarization, cyclic voltammetry, AC impedance, and microstructure analysis. Among the tested MEAs with various cathode Pt loadings (0.02–0.4 mg cm−2), the one with 0.1 mg-Pt cm−2 (grain size = 3.90 nm, mainly Pt(111)) exhibited the best cell performance (320 and 285 mW cm−2 at 0.44 and 0.60 V, respectively), which was similar to or better than those of some commercial nonsputtered/sputtered electrodes with the same or higher Pt loadings. The electrode Pt utilization efficiency increased as the Pt loading decreased. A Pt loading of greater than or lower than 0.1 mg cm−2 yielded a lower electrode electrochemical active surface (EAS) area but a higher charge transfer and diffusion resistance. Nafion impregnation (0.1 to 0.3 mg cm−2) into the sputtered Pt layer (Pt = 0.1 mg cm−2) noticeably increased the EAS area, consistent with the decrease of the capacitance of the electrode double layer, but did not improve MEA/cell performance, mainly because of the increase in the kinetic and mass transfer resistances associated with oxygen reduction on the cathode. Copyright © 2011 John Wiley & Sons, Ltd.

Color control of emissions from rare earth-co-doped La 2O 3:Bi phosphor thin films prepared by magnetron sputtering

Multicolor photoluminescence (PL) and electroluminescence (EL) were observed from developed Bi- and rare earth (RE)-co-doped La 2O 3 (La 2O 3:Bi,RE) phosphor thin films. The phosphor thin films were prepared with various contents of co-doped RE, such as Dy, Er, Eu, Tb and Tm, by a combinatorial radio frequency magnetron sputtering deposition method. The obtainable luminance in EL and PL intensities changed considerably as the kind and content of RE were varied. Color changes from blue and blue-green to various colors in PL and EL emissions, respectively, were obtained in postannealed La 2O 3:Bi,RE phosphor thin films: films prepared by co-doping Bi at a constant content with various REs at varying levels of content. However, all of the observed emission peaks in PL and EL from La 2O 3:Bi,RE phosphor thin films were assigned to either the broad emission originating from the transition in Bi 3+ or the visible emission peaks originating from the transition in the co-doped trivalent RE ion. The difference between PL and EL characteristics in La 2O 3:Bi,RE phosphor thin films is mainly attributed to the difference in the excitation mechanism.

Wafer-Scale Growth of ITO Nanorods by Radio Frequency Magnetron Sputtering Deposition

We demonstrate synthesis of tin-doped indium oxide (ITO) nanorods on 2-in. glass wafers via radio frequency (rf)-magnetron sputtering deposition. The nanorods possessed a single-crystal structure of bixbyite, grew along the <100> orientation of the cubic unit cell, and were vertically aligned to the substrates. Height and diameter of the nanorods were as large as ∼810 nm and 40–100 nm, respectively. The morphological, structural, compositional, optical, and electrical properties of the ITO nanorods were examined with respect to growth temperature (25–500°C) and growth time (10–60 min). ITO nanorod films synthesized at 500°C exhibited excellent electrical and optical property such as a low sheet resistance (∼41 Ω/□) and high transparency in the wavelength range of visible light (i.e., ∼87% transmission at 550 nm). The facile approach to synthesize ITO nanorods at a large scale demonstrated in this work may find various applications including the fabrication of high performance optoelectronic devices.