Search

In this paper, we present the results of in situ temperature measurements of resistivity for some amorphous or partially crystalline Heusler alloy (HA) films: [Co.sub.2] CrAl, [Co.sub.2] MnGa, and off-stoichiometric [Ni.sub.2][Mn.sub.1+x][Sn.sub.1-x], [Ni.sub.2][Mn.sub.1+x][Ga.sub.1-x] that are known to exhibit half-metallic properties and martensitic transformations, respectively. From resistivity p versus T characteristics we distinguish various stages of chemical and structural ordering in the films. They appear to be quite distinct in both systems investigated due to differences in their electronic structure. The resistivity results are compared with magnetic characteristics for [Co.sub.2] MnGa with a high Curie temperature. High-temperature resistivity measurement is a sensitive tool for tracing the chemical and structural ordering in HA films. Index Terms--Heusler alloys (HAs), ordering, resistivity, thin films.

Elevated temperature is a key aging factor for metallized polymer film capacitors with the capacitor life expectancy halved with every 8[degrees]C of temperature rise. For film capacitors in service, both application of a time-varying external voltage and the extinction of internal breakdown events can deposit significant heat onto the capacitor structure leading to an undesirable temperature rise. Often such heat generation is localized spatially and the resulting temperature gradient enhances the probability of subsequent breakdowns. To facilitate a thorough and generic understanding, a thermal model of metallized film capacitors is developed to simulate the dynamics of heat generation and transfer under the switching impact of an external voltage. Thermal processes in solids (polymer layers, electrode coating, and zinc-spray segment) are modeled with conduction mechanism, whereas convection mechanism is considered for silicone oil and air. Heat generation is induced either by ohmic losses of the externally applied electric field, or by internal breakdown events within the metallized film capacitor structure. This allows a seamless interface between the heat transfer model and the equivalent circuit based field calculation model. Based this electrothermal model, numerical examples are used to study temperature distribution within film capacitors and then to examine the likelihood of localized temperature hot-spots that may lead to spatially preferential breakdowns. Index Terms--Film capacitors, breakdown, heat transfer, film metallization.

In this article the structure and the magnetic properties of Ni2MnGa films deposited on mica substrates, is presented and discussed. The results are discussed in terms of a qualitative model that combines the ferromagnetic resonance with a specific microstructure of the polycrystalline Ni2MnGa film.

In this paper, an equivalent circuit model is used to simulate electrical responses of metalized polymer film capacitors to either ac voltage or pulsed voltage stresses, in particular electric field induced on the electrode coating surface and power dissipation within the film capacitor Electrode segmentation patterns are taken into consideration by means of arrays of interconnected lumped surface resistors, and the film capacitance is modeled by a set of shunt capacitors distributed across the length of the capacitor film. Voltage magnitude and waveform characteristics are studied in great detail for their effects on surface electric field and power dissipation. Through numerical examples, surface electric field and dissipated power induced by one type of external stresses (ac or pulsed) at one frequency are shown to correlate to that at a different frequency. Further correlation is also established to relate surface field and dissipated power induced by one type stress (e.g. ac) to those by the other (pulsed), provided the waveform characteristics of the two different stresses are specifically related. These numerically established correlations can permit significant reduction in development time of metalized film capacitors.

Structural disorder effects on the transport properties of Co0.50Ti0.50 alloy films were studied.

Magneto-optical spectroscopy and x-ray diffraction were used to study solid state reactions in Ti/Ni multilayered films.

A new study investigates the magneto-optical properties of Co-Pt alloy films at low and ambient temperatures.

A noncontact dry laser cleaning technique used for removing sidewall and bottom polymers effected by reactive ion etching of via holes is presented. This wafer cleaning technology uses a pulsed excimer laser irradiation at 248 mm. and has the capacity to eliminate via-etch-induced polymers by sub-threshold ablation, including fluences restricted by the damage threshold of the underlying Al-Cu metal film with titanium nitride antireflective coating. It was also observed that its ablation performance improves when irradiating at an angle.

The structural order-disorder transition in the cobalt-rich beta-phase cobalt-aluminum alloy films was analyzed with regard to their influence on their physical properties such as magnetic, magneto-optical and optical properties. Vapor quenching deposition onto glass substrates which were cooled by liquid nitrogen was applied to determine the disordered state of the alloy. Results revealed that the loss of translational invariance in the disordered state led to significant alterations in the physical properties of the cobalt-aluminum alloy films.

A study was conducted on the effects of order-disorder structural transition on nearly equiatomic FeAl alloy films' optical, magneto-optical and magnetic properties. FeAl alloy films was vapor quenching deposited onto liquid nitrogen-cooled glass substrates to produce the disordered state. The structural defect approach and electronic structure first-principle calculations were accomplished to examine the impact in the energy range 0.5-5.0 eV at room temperature.