Research Trends in Contemporary Materials Science

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Authors: Osamu Umezawa, Kohmei Halada, Yoshikazu Shinohara
Abstract: The concept of environmental conscious materials, ecomaterials, is reviewed. It has dispersed and recognized in the world as contributing to a sustainable society. Advanced models for secondary materials utilization, environmental benign processes and new material recycling systems are introduced.
Authors: D. Sarkar, J.M. Calleja, H.P. van der Meulen, J.M. Becker, R.J. Haug, Klaus Pierz
Authors: E.F. Sheka
Abstract: A unified theoretical and/or computational odd-electrons approach is suggested for molecules, surfaces and magnetic solids making possible their consideration on the same conceptual basis as well as on the same computational footing. The current paper presents the approach application to the chemistry of fullerenes, carboneous nanotubes, surface science of silicon crystal, as well as to the molecular magnetism of both solid polymerized fullerenes and molecular crystals composed of transitional metal complexes.
Authors: F. Borsetto, B. Kosmala, T.G. Fitzgerald, Matthew T. Shaw, J. Patterson, P. Rapposelli, J.M. O´Callaghan, J.D. Holmes, Michael A. Morris
Abstract: Polystyrene-polymethylmethacrylate (PS-PMMA) block copolymers are well known to exhibit microphase separation to form a series of regular structures with local periodic arrangements of the blocks. By developing films of PS-PMMA within topographically patterned silicon (100) substrates (with photolithographically defined rectangular channels of depth 60 nm and widths 166 – 433 nm) these irregular arrangements form highly periodic structures where the features are parallel to the side walls of the channels. However, the use of silicon substrates leads to problems in processing of these films. PS-PMMA does not wet the surface, and this results in island formation on flat substrates. On channel etched substrates this phenomena ensures that the thickness of the films is irregular and poorly defined alignment is seen. Detailed considerations of this polymer system suggest that feature sizes below 25 nm are not realisable. The results suggest other copolymer systems should be studied.
Authors: M. Novaković, M. Popović, D. Peruško, I. Radović, V. Milinović, M. Milosavljević
Abstract: We present a study of the micro-structural changes induced in Cr-N layers by irradiation with argon ions. The layers were deposited by reactive ion sputtering on (100) Si wafers, to a thickness of 240-280 nm, at different nitrogen partial pressures and different substrate temperatures. The samples were subsequently irradiated with 120 keV Ar+, to 1x1015 and 1x1016 ions/cm2. Structural characterization was performed with Rutherford backscattering spectroscopy, x-ray diffraction analysis and transmission electron microscopy, and we also did electrical resistivity measurements on the samples. It has been found that the layers grow in the form of a polycrystalline columnar structure, with a columnar width of a few tens of nm. The layer composition, Cr2N or CrN, strongly depends on the nitrogen partial pressure during deposition. Ion irradiation induces local micro-structural changes, formation of nano-particles and defects, though the structures retain their polycrystalline nature. The induced crystalline defects yield an increase of electrical resistivity after ion irradiation.
Authors: J. Radovanović, V. Milanović, Z. Ikonić, D. Indjin
Abstract: In this paper we have analyzed the possibility of enhancing spin-polarization performance of conventional nonmagnetic semiconductor heterostructures which rely on the resonant tunneling mechanism. Both the bulk inversion asymmetry (BIA) and the structural inversion asymmetry (SIA) effects are taken into account in the presented model. The aim is to engineer nanostructures with maximal degree of spin separation in the electron tunneling current, which might be useful in studying various spin-related phenomena in semiconductor materials. Spin-polarization status of the current, in the devices under consideration, should be controllable by moderate emitter-collector voltages. Additionally, the spin orbit-interactions affect the dwell times of electrons in spin-up and spin-down states, therefore the prospects of spin-filtering in the time domain may be considered as well.

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