Recent Developments in Advanced Materials and Processes

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Authors: V. Uskoković, Miha Drofenik
Abstract: Investigations of the influence of synthesis procedures and LaSr-manganite stoichiometries on the Curie point and other magnetic characteristics of the material, being the topic of this work, are attractive since they present a necessary primal step in the intended development of nano-magnetic drug carriers based on these materials. In the course of such an investigation, differences in the mechanisms of the formation of desired manganite compounds by following a classical solid-state preparation method, depending on various stoichiometries used, were noticed, with the reaction pathways thereof outlined onward.
Authors: Z.Ž. Lazarević, B.D. Stojanović, José Arana Varela
Abstract: Our efforts were directed to the preparation of bismuth titanate – Bi4Ti3O12 (BIT) by mechanically assisted synthesis. The mechanical activation was applied to prepare bismuth titanate, Bi4Ti3O12, from bismuth oxide, Bi2O3, and titanium oxide, TiO2 (in an anatase crystal form). Mechanochemical synthesis was performed in a planetary ball mill in air atmosphere. Bismuth titanate ceramics was obtained by sintering at 1000 oC. The formation of Bi4Ti3O12 in the sintered samples was confirmed by X-ray diffraction analysis. Scanning electron microscopy, SEM, was used to study the particle size and powder morphology. The obtained results indicate that Bi4Ti3O12 from the powder synthesized by high-energy ball milling exhibits good sinterability, showing advantage of the mechanochemical process over conventional solid-state reaction.
Authors: N. Obradović, Nebojsa Labus, Tatjana Srećković, Momcilo M. Ristić
Abstract: The influence of tribophysical activation on Zn2TiO4 synthesis along with the changes in powders during tribophysical treatment was observed. Mixtures of ZnO and TiO2 powders were mechanically activated using a high-energy ball mill at different time intervals from 0 to 300 minutes. XRD was performed in order to obtain information about phase composition variations. Microstructure parameters were revealed from an approximation method. Particle size distribution along with scanning electron microscopy gave very useful information about powder morphology.
Authors: Hyoun Woo Kim, S.H. Shim, C. Lee
Abstract: This study shows the effect of thermal annealing on GaN/ZnO/Si structures prepared by rf magnetron sputtering. Thermal annealing tended to induce a different crystalline orientation from the c-axis orientation observed with as-deposited films. The sample annealed at 900 oC under excitation at 325 nm showed two emission bands centered at approximately 380 and 550 nm.
Authors: Hyoun Woo Kim, Ju Hyun Myung, S.H. Shim, Woon Suk Hwang
Abstract: In2O3 materials consisting of dense arrays of vertically aligned rod-like structures were deposited on sapphire substrates by thermal chemical vapor deposition (CVD) using triethylindium (TEI) and oxygen as precursors at a substrate temperature of 350 oC. The rod-like structure with a triangular cross section had a cubic structure, exhibiting preferred crystallographic orientation in the [111] direction. The photoluminescence spectra of In2O3 structures under excitation at 325 nm revealed a visible emission.
Authors: I. Radović, Yves Serruys, Yves Limoge, Olivier Jaoul, N.Ž Romčević, S. Poissonnet, N. Bibić
Abstract: SiO2 layers were deposited by reactive d.c ion sputtering (using 1keV Ar+ ion gun) from a high purity silicon target in an oxygen ambient. The base pressure in the deposition chamber was 4.7·10-9mbar, and the substrate temperature was held at 550 °C. The argon partial pressure during ion gun operation was 1·10-3mbar. Structural characterization of the films was performed by Rutherford backscattering spectrometry (RBS analysis), electron microprobe analysis, X-ray diffraction (XRD analysis) and Raman spectroscopy. Reactive sputtering proved to be efficient for the deposition of silica at an oxygen partial pressure of 2·10-4mbar and an electrical current on the target of 5.5mA.
Authors: V. Milinović, M. Milosavljević, M. Popović, M. Novaković, D. Peruško, I. Radović, N. Bibić
Abstract: In this paper we present a study of the formation of TiN thin films during the IBAD process. We have analyzed the effects of process parameters such as Ar+ ion energy, ion incident angle, Ti evaporation rates and partial pressure of N2 on preferred orientation and resistivity of TiN layers. TiN thin films were grown by evaporation of Ti in the presence of N2 and simultaneously bombarded with Ar+ ions. Base pressure in the IBAD chamber was 1⋅10-6 mbar. The partial pressure of Ar during deposition was (3.1 – 6.6)⋅10-6 mbar and partial pressure of N2 was 6.0⋅10-6 - 1.1⋅10-5 mbar. The substrates used were Si (100) wafers. TiN thin layers were deposited to a thickness of 85 – 360 nm at deposition rates of Ti from 0.05 to 0.25nm/s. Argon ion energy was varied from 1.5 to 2.0 keV and the angle of ion beam incidence from 0 to 30o. All samples were analyzed by Rutherford backscattering spectrometry (RBS). The changes in concentration profiles of titanium, nitrogen and silicon were determined with 900 keV He++ ion beam. The RBS spectra were analyzed with the demo version of WiNDF code. We have also used X-ray diffraction (XRD) for phase identification. The resistivity of samples was measured with four-point probe method. The results clearly show that TiN thin layer grows with (111) and (200) preferred orientation, depending on the IBAD deposition parameters. Consequently, the formation of TiN thin layers with wellcontrolled crystalline orientation occurs. Also, it was found that the variations in TiN film resistivity could be mainly attributed to the ion beam induced damage during the IBAD process.
Authors: B. Gaković, I. Pongrac, S. Petrović, D. Minić, M. Trtica
Abstract: In this work we investigated the interaction of ns laser pulses (TEA CO2 and Nd:YAG) with a titanium nitride (TiN) thin film. The TiN thin film of 1μm thickness was deposited by PVD method on silicon substrate. Modification of TiN film was induced by laser pulses with power densities of about 108 and 109 W/cm2. Part of the laser energy absorbed on the target surface was converted into thermal energy and effects such as melting, vaporization and exfoliation were observed. Nd:YAG laser produced craters with sharp periphery, while TEA CO2 laser created damages with broad boundary zone. Hydrodynamic effects were especially pronounced during irradiation with TEA CO2 laser.
Authors: M. Trtica, B. Gaković, D. Maravić, D. Batani, T. Desai, R. Redaelli
Abstract: The effects of an Nd:YAG laser interaction with titanium target using laser radiation at wavelengths 1.064 or 0.532 μm (40 picoseconds pulse duration) were studied. Modification of target surfaces at laser energy densities of 2.4 and 10.3 J/cm2 (λ1 laser= 1.064 μm) and 1.1 J/cm2 (λ2 laser= 0.532 μm) are reported in this article. Qualitatively, the titanium surface modification can be summarized as follows: (i) ablation of the titanium surface in the central zone of the irradiated area for both laser wavelengths; (ii) appearance of a hydrodynamic feature like resolidified droplets of the material (λ1 laser= 1.064 μm), as well as formation of the wave-like microstructures (λ2 laser= 0.532 μm); and (iii) appearance of plasma, in front of the target, with both laser wavelengths.
Authors: Philippe Goldner, Olivier Guillot-Noël
Abstract: Quantum information uses special properties of quantum systems to manipulate or transmit data. This results in new processes, which are impossible to obtain with classical devices. For example, quantum computing and quantum storage, which are two important fields in quantum information research, aim respectively at performing very fast calculations and at storing quantum states of photons. These two applications could be obtained in solid-state systems using rare earth doped crystals. In this context, the most important property of these materials is the long coherence lifetimes of rare earth ion optical and hyperfine transitions. This allows one to create long-lived superposition states, which is a fundamental requirement for efficient quantum computing and storage. Promising results have already been demonstrated in rare earth doped crystals but it will be difficult to improve them with current materials. In this paper, we discuss the general and specific requirements for rare earth ions and crystals in order to perform quantum computing with a large number of quantum bits as well as all solid-state quantum storage. We also present the properties of a few recently studied crystals: Ho3+:YVO4, Ho3+:LuVO4 (quantum computing) and Tm3+:Y3Al5O12 (quantum storage).

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