National Institute Of Materials Physics - Romania

Publications

5781 articles found

1631. Transparent field-effect transistors based on AlN-gate dielectric and IGZO-channel semiconductor

Authors: Besleaga, C; Stan, GE; Pintilie, I; Barquinha, P; Fortunato, E; Martins, R

Published: AUG 30 2016, APPLIED SURFACE SCIENCE, 379, 276, DOI: 10.1016/j.apsusc.2016.04.083

The degradation of thin-film transistors (TFTs) caused by the self-heating effect constitutes a problem to be solved for the next generation of displays. Aluminum nitride (AlN) is a viable alternative for gate dielectric of TFTs due to its good thermal conductivity, matching coefficient of thermal expansion to indium-gallium-zinc-oxide, and excellent stability at high temperatures. Here, AlN thin films of different thicknesses were fabricated by a low temperature reactive radio-frequency magnetron sputtering process, using a low cost, metallic Al target. Their electrical properties have been thoroughly assessed. Furthermore, the 200 nm and 500 nm thick AlN layers have been integrated as gate-dielectric in transparent TFTs with indium-gallium-zinc-oxide as channel semiconductor. Our study emphasizes the potential of AlN thin films for transparent electronics, whilst the functionality of the fabricated field-effect transistors is explored and discussed. (C) 2016 Elsevier B.V. All rights reserved.

1632. Combined ab initio and XPS Investigations of the Electronic Interactions of L-Cysteine Adsorbed on GaAs(100)

Authors: Juarez, MF; Toader, AM; Negrila, C; Santos, E; Lazarescu, V

Published: AUG 16 2016, CHEMISTRYSELECT, 1, 3634, DOI: 10.1002/slct.201600589

The adsorption of L-cysteine from ethanol solutions on GaAs(1 0 0) surfaces has been studied by XPS and density-functional theory (DFT). XPS data reveal that the formation of the adsorbate involves preferentially the As-sites for p-GaAs(1 0 0) and the Ga-sites for n-GaAs(1 0 0). The adsorbed species show different orientations of the functional groups to the surface for the different substrates. DFT calculations performed for both Ga-dimers and As-dimers terminated surfaces show that the adsorption is energetically favourable on both substrates. However, the adsorption energy is more negative on top of Ga-atoms. Here an important contribution for the stabilization of the adsorbate is the interaction of the functional groups with the surface. The parallel orientation found for the Ga-bound species by DFT calculations is in good agreement with the shift in the binding energy of the NH2/NH3+ species observed by XPS analysis.

1633. New-developed TiO2-based photocatalytic nano particles exhibit biocompatibility on MRC-5 lung fibroblasts after short-term exposure

Authors: Dinischiotu, A; Nica, CI; Stan, MS; Dumitrescu, I; Diamandescu, L

Published: AUG 10 2016, JOURNAL OF BIOTECHNOLOGY, 231, S67, DOI: 10.1016/j.jbiotec.2016.05.246

1634. Rise in power of Yb:YCOB for green light generation by self-frequency doubling

Authors: Khaled, F; Loiseau, P; Aka, G; Gheorghe, L

Published: AUG 1 2016, OPTICS LETTERS, 41, 3610, DOI: 10.1364/OL.41.003607

Spectroscopic properties and self-frequency-doubling laser performance are presented for Yb:YCa4O(BO3)(3) (Yb:YCOB) crystals oriented for type I second-harmonic generation in the ZX plane. In a plane-concave cavity 10 cm long, up to 330 mW of green light (544.5 nm) is obtained for 14.7 W of laser diode incident pump power. Broad emission bands and weak anisotropy in the 1060-1100 nm range between the two eigenstates of polarization may explain the instability of the self-frequency-doubled output power. (C) 2016 Optical Society of America

1635. Ferritin surplus in mouse spleen 14 months after intravenous injection of iron oxide nanoparticles at clinical dose

Authors: Tamion, A; Hillenkamp, M; Hillion, A; Maraloiu, VA; Vlaicu, ID; Stefan, M; Ghica, D; Rositi, H; Chauveau, F; Blanchin, MG; Wiart, M; Dupuis, V

Published: AUG 2016, NANO RESEARCH, 9, 2410, DOI: 10.1007/s12274-016-1126-6

In this study, we followed the biodegradation of ultra-small superparamagnetic iron oxide nanoparticles injected intravenously at clinical doses in mice. An advanced fitting procedure for magnetic susceptibility curves and low-temperature hysteresis loops was used to fully characterize the magnetic size distribution as well as the magnetic anisotropy energy of the injected P904 nanoparticles (Guerbet Laboratory). Additional magnetometry measurements and transmission electronic microscopy observations were systematically performed to examine dehydrated samples from the spleen and liver of healthy C57B16 mice after nanoparticle injection, with sacrifice of the mice for up to 14 months. At 3 months after injection, the magnetic properties of the spleen and liver were dramatically different. While the liver showed no magnetic signals other than those also present in the reference species, the spleen showed an increased magnetic signal attributed to ferritin. This surplus of ferritin remained constant up to 14 months after injection.

1636. Effect of polyhedral oligomeric silsesquioxane nanoreinforcement on the properties of epoxy resin/monoglycidylether-terminated poly(dimethylsiloxane) nanocomposites

Authors: Florea, NM; Lungu. A; Balanuca, B; Badica, P; Craciun, L; Damian, CM; Enculescu, M; Ionescu, C; Tihan, G; Iovu, H

Published: AUG 2016, HIGH PERFORMANCE POLYMERS, 28, 734, DOI: 10.1177/0954008315595447

This article reports the synthesis and characterization of several types of organic-inorganic nanocomposites based on epoxy resin/monoglycidylether-terminated poly(dimethylsiloxane) reinforced with 2, 5, or 10 wt% polyhedral oligomeric silsesquioxanes (POSS) bearing one glycidyl (1GE-POSS) or eight glycidyl(8GE-POSS) groups. The morphological features of the studied samples were established through atomic force microscopy, contact angle measurements, X-ray photoelectron spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy, and it was demonstrated that 8GE-POSS is well dispersed within the polymer matrix, while 1GE-POSS exhibits a high tendency to form aggregates. Differential scanning calorimetry (DSC) and Fourier transform infrared resonance (FTIR) measurements are used to follow the curing behavior and to study the polymerization kinetics of epoxy groups. As evidenced by DSC and FTIR results, the inclusion of 8GE-POSS within the polymer matrix leads to a lower epoxy polymerization rate of the resulted nanocomposites than those reinforced with 1GE-POSS. The dynamic mechanical analysis results revealed that the thermomechanical properties are gradually improved with increasing of 8GE-POSS content due to the higher cross-linking density.

1637. Low level NO2 detection under humid background and associated sensing mechanism for mesoporous SnO2

Authors: Stanoiu, A; Somacescu, S; Calderon-Moreno, JM; Teodorescu, VS; Florea, OG; Sackmann, A; Simion, CE

Published: AUG 2016, SENSORS AND ACTUATORS B-CHEMICAL, 231, 174, DOI: 10.1016/j.snb.2016.02.137

Mesoporous SnO2 prepared by a hydrothermal synthesis route assisted by the ionic surfactant Cetyltrimethylammonium bromide, has rutile-type tetragonal symmetry, small homogeneous nanocrystallite size of similar to 4 nm and good thermal stability. Porosity analysis revealed high surface area similar to 127 m(2)/g and a narrow pore size distribution, with an average pore diameter similar to 4 nm. The mesoporous structure is likewise advantageous towards enhancing the surface reactivity and subsequent gas sensing performances. The role played by the surface hydroxylation on the NO2 sensing mechanism was discussed with respect to the associated photoelectron spectral components. Under humid air, associated with the in-field conditions, the highest sensitivity was attained at 150 degrees C, were the sensor signal towards NO2 is 4 times higher than the one recorded in dry air. This feature has been experimentally demonstrated by simultaneous electrical resistance and work function changes measurements conducted in the range of 400-5000 ppb NO2. (C) 2016 Elsevier B.V. All rights reserved.

1638. Finite element analysis of a modified short hip endoprosthesis

Authors: Semenescu, A; Radu, FI; Mates, IM; Badica, P; Batalu, ND

Published: AUG 2016, ROMANIAN JOURNAL OF MILITARY MEDICINE, 119, DOI:

A finite element simulation of the mechanical static features for a modified short hip endoprosthesis was performed. The corkscrew-like femoral stem was modified introducing more turns of the thread. By such an approach it is expected that for some cases the mechanical fixation of the prosthesis to the bone will be improved or the use of the cement for bonding is not necessary. Our scenario was estimated for titanium and stainless steel, and both materials show good safety factors. Mechanical stress is expected to be distributed more uniform in the bone for the new design with more turns of thread.

1639. Effects of magnetic dipolar interactions on the specific time constant in superparamagnetic nanoparticle systems

Authors: Iacob, N; Schinteie, G; Bartha, C; Palade, P; Vekas, L; Kuncser, V

Published: JUL 27 2016, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 49, DOI: 10.1088/0022-3727/49/29/295001

A quantitative treatment of the effects of magnetic mutual interactions on the specific absorption rate of a superparamagnetic system of iron oxide nanoparticles coated with oleic acid is reported. The nanoparticle concentration of the considered ferrofluid samples varied from a very low (0.005) to a medium (0.16) value of the volume fraction, whereas the amplitude of the exciting AC magnetic field ranged from 14-35 kA m(-1). It was proved that a direct effect of the interparticle interactions resides in the regime of the modified superparamagnetism, dealing, besides the usual increase in the anisotropy energy barrier per nanoparticle, with the decrease in the specific time constant tau(0) of the relaxation law, usually considered as a material constant. Consequently, the increase in the specific absorption rate versus the volume fraction is significantly diminished in the presence of the interparticle interactions compared to the case of non-interacting superparamagnetic nanoparticles, with direct influence on the magnetic hyperthermia efficiency.

1640. Defect induced tunable near infrared emission of Er-CeO2 by heterovalent co-dopants

Authors: Florea, M; Avram, D; Cojocaru, B; Tiseanu, I; Parvulescu, V; Tiseanu, C

Published: JUL 21 2016, , DOI: 10.1039/c6cp02754g