Papers by Keyword: Multilayer Thin Film

Abstract: A focused ion beam (FIB) mill equipped with a microsampling (MS) unit and combined with transmission electron microscopy (TEM)/scanning TEM-energy dispersive x-ray spectroscopy (STEM-EDXS) is a powerful tool for studies of the functional advanced materials. For the studies, the specimen must be prepared as a thin foil which is tranparent to the electron beam. Focused ion beam is very effective method for fabricating TEM specimen of the cross-sectional thin film with the “lift-out” technique using a tungsten (W)-needle probe as a micromanipulator. A multilayer film of MgB₂/Ni deposited on a Si (001) substrate prepared by FIB-MS technique is presented. Before FIB fabrication, the surface of the multilayer film was coated with W-film to prevent the surface from bombardment by the ion beam. A bright field (BF)-STEM image of the multilayer film related to two-dimensional (2D) elemental mapping clearly showed the presence of MgB₂-and Ni-nanolayers. The measured experimental spacing between Ni-nanolayers was comparable with the actual specimen design, but the thickness of Ni-nanolayer was not. Unexpected nanostructures of the formation of SiO₂ film on the substrate surface and holes within the film were observed.

Abstract: Rate of SHS (self-propagating high-tеmperature synthesis) reactions in solid nano-sized multilayers is controlled by the time and temperature dependent vacancy concentration. The increase of reaction temperature is typically faster than the rate of vacancy generation. Therefore, the finite relaxation rate of vacancies leads to drastic slowing down of SHS. On the other hand, as-prepared vacancy supersaturation due to fast deposition on the cold substrate may lead to a certain acceleration of SHS. Influence of (1) vacancy mean free path and (2) initial vacancy supersaturation on the SHS rate is investigated numerically. In wide region of parameters the front velocity appears to be inversely proportional to the square root of vacancy mean free path length.

Abstract: In order to study the characteristics of multilayer thin films with a ZnO/ metal/ ZnO structure the manufacture of the thin films was performed by a dc (direct current) magnetron sputtering system on slide glass substrates. The ZnO thin films were manufactured with the thicknesses of 30 nm and 50 nm. Three kinds of metals (Ag, Al and Cu) were deposited with the thicknesses of 4 nm, 8 nm, 12 nm and 16 nm. The electrical and optical properties of the manufactured thin films were then observed. As a result, the multilayer thin films with an Ag layer represented the most excellent electrical conductivity. This is due to the difference in the fundamental electrical properties of each of the metals. The structures of the metal particles deposited on the ZnO thin films were observed by an SEM (scanning electron microscope). The thin films exhibited a continuous structure with regular spaces between the metal particles. This resulted in an increase of transmittance. This is considered by the decrease of scattering and of light absorption on thin films with a continuous structure.

Abstract: Joining nickel based superalloys to gamma-TiAl intermetallic alloys will contribute to a more efficient application of these advanced materials, particularly in extreme environments. In this study, Inconel alloy and gamma-TiAl are joined using as filler alternated nanolayer thin films deposited onto each base material. The nanolayers consisted in Ni/Al exothermic reactive multilayer thin films with periods of 5 and 14 nm deposited by d.c. magnetron sputtering in order to improve the adhesion to the substrates and to avoid the reaction between Ni and Al. Diffusion bonding experiments with multilayer coated alloys were performed under vacuum at 800°C by applying 50 MPa during 1h. Bonding was achieved in large areas of the centre of the joints where regions without cracks or pores were produced, especially when using multilayer thin films with a 14 nm modulation period.

Abstract: Interdiffusion in Fe/Pt multilayer thin films has been studied. [Fe(1nm)/Pt(1.5nm)]20 multilayers were prepared by DC magnetron sputtering technique and subsequently annealed at temperatures of 543 - 633K in vacuum lower than 10-6 torr. X-ray diffraction (XRD) studies on these multilayer systems revealed the interdiffusion coefficients from slope of the best straight line fit of first peak intensity versus annealing time. The temperature dependence of interdiffusion in the range of 543 - 633K can be described by D=4.98×10-24 exp (0.88eV/kT) m2S-1. The coercivity, measured by Vibrating Sample Magnetometer, of the multilayer with annealing time at 603K increased, which is believed to the increase of surface roughness by interdiffusion at the interfaces of Fe and Pt multilayers, enhancement of composition gradient; and/or formation of Fe-Pt reaction phase at the interface of Fe and Pt.