Frequency Magnetron Sputtering Deposition Method Research Articles

Nonlinear optical properties and passively Q-switched laser application of a layered molybdenum carbide at 639 nm.

Molybdenum carbide (Mo2C) exhibits enormous potential applications in various optoelectronic and photonic fields due to its remarkably electrical and optical characteristics. Here, we fabricate a high-quality Mo2C film by the radio frequency magnetron sputtering deposition method. The nonlinear optical response and ultrafast dynamics are thoroughly studied based on open-aperture Z-scan and nondegenerate pump-probe experimental measurements. The open-aperture Z-scan experimental result exhibits a modulation depth of 8.5% and a saturation fluence of 0.28 mJ/cm2. Simultaneously, the relaxation time constant is fitted by a biexponential decay function, showing an ultrafast intraband carrier recovery time of 0.58 ps at 530 nm. Consequently, by employing the Mo2C film as a saturable absorber (SA), stable Q-switched Pr:YLF laser pulses with the shortest pulse width of 160 ns are generated at 639 nm. Our experimental results demonstrate excellent nonlinear optical properties of the layered Mo2C in the visible region and will further advance their potential applications in visible nonlinear optics.

Micro-patterned 3D Si electrodes fabricated using an imprinting process for high-performance lithium-ion batteries

To overcome the volumetric expansion of Si used as an anode in lithium-ion batteries (LIBs), we propose 3D Si electrode structures formed on patterned Cu current collectors designed from metal molds fabricated using wire electrical discharge machining (WEDM). The line- and check-patterned Cu current collectors with microscale periods for LIBs are prepared using an imprinting technique with patterned metal molds fabricated using the WEDM process. The line- and check-patterned Si thin-film and powder-type electrodes as anodes are fabricated using radio frequency magnetron sputtering deposition method and conventional slurry casting process, respectively. The morphology of the Si electrodes before and after the cycling process is characterized using optical microscopy and scanning electron microscopy. The electrochemical properties of the Si electrodes are evaluated using a multi-channel battery tester and electrochemical impedance analyzer. In particular, the check-patterned Si electrodes exhibit relatively high-capacity and enhanced cycling performance due to the stress relief of the Si anode.

Effect of surface carbon contamination on the chemical states of N-doped ZnO thin films

Nitrogen-doped ZnO thin films [ZnO:N] and intentional surface carbon-contaminated ZnO:N thin films [ZnO:N@C] were grown on quartz substrates by radio frequency magnetron sputtering deposition method. The structural, electrical and optical properties as well as chemical states of elements were investigated by means of X-ray diffraction (XRD), Hall effect measurement (Hall), UV–Vis–Near infrared spectrophotometer and X-ray photoelectron spectroscopy (XPS). The results indicate that surface carbon contamination almost does not affect the band gap of ZnO:N thin films but has a strong impact on the crystal quality of ZnO:N thin film surface and results in a significant increase in tensile stress. The XPS analysis shows that the effect of surface carbon contamination treatment on the chemical states of ZnO:N thin films is remarkable. Because the stability of Zn–N bonds in N-rich local environments is nowhere near that of those in O-rich local environments, the N atoms in N-rich local environments easily bond with surface carbon atoms to form undesirable C–N bonds, thus resulting in a decrease of NO acceptors in N-rich local environments. Obviously, it is unfavorable to subsequently prepare high stability of N-doped p-type ZnO thin films.

In situ Electrochemical-AFM Study of LiFePO4 Thin Film in Aqueous Electrolyte.

Lithium-ion (Li-ion) batteries have been widely used in various kinds of electronic devices in our daily life. The use of aqueous electrolyte in Li-ion battery would be an alternative way to develop low cost and environmentally friendly batteries. In this paper, the lithium iron phosphate (LiFePO4) thin film cathode for the aqueous rechargeable Li-ion battery is prepared by radio frequency magnetron sputtering deposition method. The XRD, SEM, and AFM results show that the film is composed of LiFePO4 grains with olivine structure and the average size of 100 nm. Charge-discharge measurements at current density of 10 μAh cm−2 between 0 and 1 V show that the LiFePO4 thin film electrode is able to deliver an initial discharge capacity of 113 mAh g−1. Specially, the morphological changes of the LiFePO4 film electrode during charge and discharge processes were investigated in aqueous environment by in situ EC-AFM, which is combined AFM with chronopotentiometry method. The changes in grain area are measured, and the results show that the size of the grains decreases and increases during the charge and discharge, respectively; the relevant mechanism is discussed.

Origin of the responsivity characteristics of the MgyZn1-yO metal-semiconductor-metal photodetectors with different electrode spacings

We fabricate MgyZn1-yO metal-semiconductor-metal ultraviolet photodetectors by integrating Au electrodes (with different electrode spacings) onto a semiconductor film (Mg0.20Zn0.80O or Mg0.42Zn0.58O), prepared by the radio frequency magnetron sputtering deposition method. As expected, the Mg0.20Zn0.80O photodetectors have a larger responsivity than the Mg0.42Zn0.58O ones when the electrode spacing and bias voltage are constant. More interestingly, the responsivity of all the MgyZn1-yO photodetectors increase with decreasing electrode spacing for the same bias. These results are well-understood in terms of the role played by the metal-semiconductor junction.

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.

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.

Photocatalytic Hydrogen Production from Aqueous Solutions of Alcohol as Model Compounds of Biomass Using Visible Light-Responsive TiO2 Thin Films

Visible light-responsive TiO2 (Vis-TiO2) thin films were prepared by a radio frequency magnetron sputtering deposition method. The photoelectrochemical performance was improved by adding various kinds and concentrations of alcohol, i.e., model compounds of biomass, to water. The separate evolution of pure H2 was observed to proceed efficiently on these Vis-TiO2 thin films under visible light irradiation by using an aqueous solution of methanol.

Preparation of Nitrogen-Substituted TiO2 Thin Film Photocatalysts by the Radio Frequency Magnetron Sputtering Deposition Method and Their Photocatalytic Reactivity under Visible Light Irradiation

Nitrogen-substituted TiO2 (N-TiO2) thin film photocatalysts have been prepared by a radio frequency magnetron sputtering (RF-MS) deposition method using a N2/Ar mixture sputtering gas. The effect of the concentration of substituted nitrogen on the characteristics of the N-TiO2 thin films was investigated by UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The absorption band of the N-TiO2 thin film was found to shift smoothly to visible light regions up to 550 nm, its extent depending on the concentration of nitrogen substituted within the TiO2 lattice in a range of 2.0-16.5%. The N-TiO2 thin film photocatalyst with a nitrogen concentration of 6.0% exhibited the highest reactivity for the photocatalytic oxidation of 2-propanol diluted in water even under visible (lambda > or = 450 nm) or solar light irradiation. Moreover, N-TiO2 thin film photocatalysts prepared on conducting glass electrodes showed anodic photocurrents attributed to the photooxidation of water under visible light, its extent depending on wavelengths up to 550 nm. The absorbed photon to current conversion efficiencies reached 25.2% and 22.4% under UV (lambda = 360 nm) and visible light (lambda = 420 nm), respectively. UV-vis and photoelectrochemical investigations also confirmed that these thin films remain thermodynamically and mechanically stable even under heat treatment at 673 K. In addition, XPS and XRD studies revealed that a significantly high substitution of the lattice O atoms of the TiO2 with the N atoms plays a crucial role in the band gap narrowing of the TiO2 thin films, enabling them to absorb and operate under visible light irradiation as a highly reactive, effective photocatalyst.

Study of the Strain in InN Thin Films Using Synchrotron X-Ray Scattering

Semiconductor InN films epitaxially grown by the radio frequency magnetron sputtering deposition method were studied in terms of the strain evolution as a function of the film thickness and growth temperature. The structure and surface morphology of the InN films were analyzed using synchrotron X-ray scattering and atomic force microscopy (AFM) experiments, respectively. The lattice strain of the InN films grown at 300°C was larger than that of the films grown at 490°C. As the film thickness increases, the lattice strain is reduced and completely relaxes when the thickness is larger than 350 Å. The average roughness on the surface of the InN film increased with the growth temperature.

Ferroelectric characteristics of SrBi 2Ta 2O 9 thin films fabricated by the radio frequency magnetron sputtering deposition technique

SrBi 2Ta 2O 9 thin films were successfully fabricated by the radio frequency magnetron sputtering deposition method. The crystal structure of SrBi 2Ta 2O 9 thin films grown on the Pt(111) layer was preferentially c-axis oriented. Surface microstructure shows the mixture of two kinds of morphologies. The Pt/SBTO/Pt capacitor shows P r *- P r ^ = 16.3 μC/cm 2 and E c=50 kV/cm. After a fatigue test, the polarization versus electric field loop shifted toward a positive electric field. The interface between platinum and titanium layer was changed by the inter-diffusion of the Pt, Ti, O atoms after post-annealing at 800°C for 2 h.