Research Trends in Contemporary Materials Science

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Authors: Jong Woo Lee, Hyoun Woo Kim, Jeong Whan Han, Mok Soon Kim, Byung Don Yoo, M.H. Kim, C.H. Lee, C.H. Lee, Cheol Ho Lim, Sun Keun Hwang, C. Lee, D.J. Chung, S.G. Park, S.G. Lee, B.H. O, J. Kim, S.P. Chang, S.H. Lee, Seung Yong Chai, Wan In Lee, S.E. Park, K. Kim, D.K. Choi, C.W. Chung
Abstract: We present a study of the photoresist (PR) etching and the low-k materials damage using a ferrite-core inductively coupled plasma (ICP) etcher, in order to develop an etching process for the low-k dielectric devices. We reveal that the N2/O2 flow ratio and bias power affected the PR etching rate. By Fourier transform infrared spectroscopy and HF dipping test, we investigated the effect of the gas flow ratio and bias power on the amount of etching damage to the low-k material.
113
Authors: G. Keković, D. Raković, David Davidović
Abstract: Our recently proposed quantum approach to biomolecular isomeric-conformational changes and recognition processes, additionally supported by biomolecular resonant recognition model and by quantum-chemical theory of biomolecular non-radiative resonant transitions, is hereby extended to cascade resonant transitions via close intermediate participating isomeric states - which might be related to polaron/soliton-like energy and charge transport mechanisms in Q1Dmolecular chains, whose relevance is explored in this paper.
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Authors: Rajko M. Šašić, P.M. Lukić
Abstract: Carriers mobility model of olygomer and polymer semiconductor based OFET (Organic Field Effect Transistor) structures is presented in this paper. Starting from the conduction mechanism in the mentioned organic materials, a carrier mobility dependence on temperature, electric field and trap density μ(T,E,NT) was investigated, inspiring directly the current-voltage I(V) model of OFET structures. Subsequent simulations were also performed and the obtained results compared with the data available in the literature.
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Authors: S. Raičević, V. Stanić, Tanja Kaludjerović-Radoičić
Abstract: Several approaches for immobilization of arsenic (As) based on the transformation of its soluble forms (compounds) into highly insoluble arsenate apatite Ca5(AsO4)3OH have been proposed. These immobilization techniques are successfully applied in treatment of industrial waste containing As. Quite the contrary, treatment of soil contaminated with As by apatite amendments, instead of immobilization of this toxic element, increases its mobility and bioavailability. The mechanism underlying these opposite effects still remains elusive. Here, the stability analysis of different calcium arsenates: Ca5(AsO4)3OH, Ca4(AsO4)2(OH)2, Ca3(AsO4)2 Ca5H2(AsO4)2 and CaHAsO4 was performed, which is based on the calculation of the ion-ion interaction potential (IIIP). It has been demonstrated earlier that IIIP, representing the main term of the cohesive energy, is a suitable parameter for assessment of mineral stability. According to the results of this analysis, arsenate apatite with IIIP value of -0.578 Ry represents the most stable chemical form among analyzed compounds. Based on this finding, we proposed a mechanism of formation of arsenate apatite in the presence of hydroxyapatite. This mechanism can explain the suitability of this approach for the treatment of industrial waste and its limitations for in situ treatment of soil and water contaminated with As.
131
Authors: Srboljub J. Stanković, R.D. Ilić, O. Ciraj-Bjelac, M. Kovačević, David Davidović
Abstract: The adequate choice of different target materials for X-ray generators is a very important subject of engineers’ practice and research. In the present work we analyze theoretically the transport of electrons through the anode material and the production of the corresponding bremsstrahlung radiation. In our analysis we simulate the particle transport with the help of the FOTELP code, which is based on the Monte Carlo simulation. Our main aim is to develop an efficient and handy method, which could be helpful in improving the design of the X-ray tube components and in reducing of the patient dose, while keeping the image quality. The obtained results are encouraging.
137
Authors: Srboljub J. Stanković, M. Petrović, M. Kovačević, A. Vasić, P. Osmokrović, B. Lončar
Abstract: CdZnTe detectors have been employed in diagnostic X-ray spectroscopy. This paper presents the Monte Carlo calculation of X-ray deposited energy in a CdZnTe detector for different energies of photon beam. In incident photon direction, the distribution of absorbed dose as deposited energy in detector is determined. Based on the dependence of the detector response on the thickness and different Zn fractions, some conclusions about changes of the material characteristics could be drawn. Results of numerical simulation suggest that the CdZnTe detector could be suitable for X-ray low energy.
141
Authors: M. Odalović, D. Petković
Abstract: The gamma-ray irradiation causes positive charge traps formation in silicon dioxide films and at silicon dioxide - silicon interface of MOS devices, and the threshold voltage shift in MOS transistors. Here, the Monte Carlo model was used to develop an approach for estimating gammaray induced traps spatially distributed in silicon dioxide films. This is combined with the model of energy distributed traps at silicon dioxide - silicon interface. The developed model enables gammaray induced charge and threshold voltage shift determination as a function of gamma-ray doses. The threshold voltage measurements at a single specified current, both of radiation sensitive and radiation hardened MOS transistors irradiated with different doses of gamma-ray are compared with the developed model and good agreement are obtained.
147
Authors: M. Sarajlić, R.M. Ramović
Abstract: Electron mobility for the silicon-based devices is one of the most important parameters, which determine the behavior of components. Mobility depends on silicon purity, doping level, presence of lattice defects and electric field in the particular device. These influences are particularly important for the nano-scaled devices since it is much more difficult to control the thickness of the active layer, uniformity of impurity doping and appearance of parasitic bipolar devices and capacitances. We have investigated a relationship between the electron mobility for the silicon based PD (Partially Depleted) SOI (Silicon On Insulator) NMOS (n-type Metal Oxide Semiconductor) Devices and the related kink effect, which appears as a consequence of the charge accumulation at the interface of the Buried Oxide. We relate PD SOI NMOS Device technology parameters to the kink effect and we propose a guiding line for alleviating this effect.
153
Authors: A.R. Tančić, M. Davidović, S. Sredić
Abstract: The calculations of the low-energy attachment cross section to metallic clusters are investigated. Low energy electrons are taken as slow enough to excite a giant dipole collective resonance within the cluster. The calculations are more refined than the earlier ones – they do not depend on the experimental data, and we improved RPAE calculation of the collective resonance in the cluster. The results are interesting for the nano-region and designing of new materials.
159
Authors: F. Skuban, S.R. Lukić, D.M. Petrović, Mirjana Šiljegović
Abstract: Transformations of glasses from the multicomponent pseudobinary system (As2Se3)100−x(SbSI)x were analyzed from the aspect of determining the glass transition temperature Tg, activation energy of the process Et, and characteristic changes of the specific heat. The established dependence of Tg on glass composition and heating rate served as the basis for determining the activation energy of glass transition process Et. An abrupt increase in the specific heat cp at the glass transition temperature was analyzed with the aim of classifying the materials according to the criterion of the so-called 'fragility'. It was found that the investigated glasses, i.e. their melts, belong to the group of thermodynamically 'strong' melts.
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