National Institute Of Materials Physics - Romania

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885 articles found

561. Silicon detectors for the sLHC

Authors: Affolder, A; Aleev, A; Allport, PP; Andricek, L; Artuso, M; Balbuena, JP; Barabash, L; Barber, T; Barcz, A; Bassignana, D; Bates, R; Battaglia, M; Beimforde, M; Bemardini, J; Betancourt, C; Bilei, GM; Bisello, D; Blue, A; Bohm, J; Bolla, G; Borgia, A; Borrello, L; Bortoletto, D; Boscardin, M; Bosma, MJ; Bowcock, TJV; Breindl, M; Broz, J; Bruzzi, M; Brzozowski, A; Buhmann, P; Buttar, C; Campabadal, F; Candelori, A; Casse, G; Charron, S; Chren, D; Cihangir, S; Cindro, V; Collins, P; Gil, EC; Costinoaia, CA; Creanza, D; Cristobal, C; Dalla Betta, GF; de Boer, W; De Palma, M; Demina, R; Dierlamm, A; Diez, S; Dobos, D; Doherty, F; Kittelmann, ID; Dolezal, Z; Dolgolenko, A; Dragoi, C; Driewer, A; Dutta, S; Eckstein, D; Eklund, L; Eremin, I; Eremin, V; Erfle, J; Fadeeva, N; Fahrer, M; Fiori, F; Fleta, C; Focardi, E; Forshaw, D; Fretwurst, E; Frey, M; Bates, AG; Gallrapp, C; Garcia, C; Gaubas, E; Genest, MH; Giolo, K; Glaser, M; Goessling, C; Golubev, A; Gorelov, I; Gregoire, G; Gregori, P; Grigoriev, E; Grillo, AA; Grinstein, S; Groza, A; Guskov, J; Hansen, TE; Harkonen, J; Hartjes, FG; Hartmann, F; Hoeferkamp, M; Horisberger, R; Houdayer, A; Hynds, D; Ilyashenko, I; Junkes, A; Kadys, A; Kaminski, P; Karpenko, A; Kaska, K; Kazuchits, N; Kazukauskas, V; Kharchuk, A; Khivrich, V; Kierstead, J; Klanner, R; Klingenberg, R; Kodys, P; Koffeman, E; Kohler, M; Kohout, Z; Korjenevski, S; Korolkov, I; Kozlowski, R; Kozubal, M; Kramberger, G; Kuhn, S; Kuleshov, S; Kuznetsov, A; Kwan, S; La Rosa, A; Lacasta, C; Lange, J; Lassila-Perini, K; Lastovetsky, V; Lazanu, I; Lazanu, S; Lebel, C; Lefeuvre, G; Lemaitre, V; Leroy, C; Li, Z; Lindstrom, G; Litovchenko, A; Litovchenko, P; Lozano, M; Luczynski, Z; Luukka, P; Macchiolo, A; Macraighne, A; Maenpaa, T; Makarenko, LF; Mandic, I; Maneuski, D; Manna, N; Marco, R; Garcia, SII; Marunko, S; Masek, P; Mathieson, K; Matysek, M; Mekki, J; Messineo, A; Metcalfe, J; Mikestikova, M; Mikuz, M; Militaru, O; Minano, M; Miyamoto, J; Moll, M; Monokhov, E; Mori, R; Moser, HG; Muenstermann, D; Sanchez, FJM; Naletko, A; Nisius, R; Oshea, V; Pacifico, N; Pantano, D; Parkes, C; Parzefall, U; Passeri, D; Pawlowski, M; Pellegrini, G; Pernegger, H; Petasecca, M; Piemonte, C; Pignatel, GU; Pintilie, I; Pintilie, L; Piotrzkowski, K; Placekett, R; Pohlsen, T; Polivtsev, L; Popule, J; Pospisil, S; Preiss, J; Radicci, V; Radu, R; Raf, JM; Rando, R; Richter, R; Roeder, R; Roger, R; Rogozhkin, S; Rohe, T; Ronchin, S; Rott, C; Roy, A; Rummler, A; Ruzin, A; Sadrozinski, HFW; Sakalauskas, S; Samadashvili, N; Scaringella, M; Schumm, B; Seidel, S; Seiden, A; Shipsey, I; Sibille, J; Sicho, P; Slavicek, T; Solar, M; Soldevila-Serrano, U; Son, S; Sopko, V; Sopko, B; Spencer, N; Spiegel, L; Srivastava, A; Steinbrueck, G; Stewart, G; Stolze, D; Storasta, J; Surma, B; Svensson, BG; Tan, P; Tomasek, M; Toms, K; Tsiskaridze, S; Tsvetkov, A; Tuboltsev, Y; Tuominen, E; Tuovinen, E; Tuuva, T; Tylchin, M; Uebersee, H; Ullan, M; Vaitkus, JV; van Beuzekom, M; Verbitskaya, E; Alvarez, IV; Visser, J; Vossebeld, J; Vrba, V; Walz, M; Weigell, P; Wiik, L; Wilhelm, I; Wunstorf, R; Zaluzhny, A; Zavrtanik, M; Zelazko, J; Zen, M; Zhukov, V; Zontar, D; Zorzi, N

Published: DEC 1 2011, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 658, 16, DOI: 10.1016/j.nima.2011.04.045

In current particle physics experiments, silicon strip detectors are widely used as part of the inner tracking layers. A foreseeable large-scale application for such detectors consists of the luminosity upgrade of the Large Hadron Collider (LHC), the super-LHC or sLHC, where silicon detectors with extreme radiation hardness are required. The mission statement of the CERN RD50 Collaboration is the development of radiation-hard semiconductor devices for very high luminosity colliders. As a consequence, the aim of the R&D programme presented in this article is to develop silicon particle detectors able to operate at sLHC conditions. Research has progressed in different areas, such as defect characterisation, defect engineering and full detector systems. Recent results from these areas will be presented. This includes in particular an improved understanding of the macroscopic changes of the effective doping concentration based on identification of the individual microscopic defects, results from irradiation with a mix of different particle types as expected for the sLHC, and the observation of charge multiplication effects in heavily irradiated detectors at very high bias voltages. (C) 2011 Elsevier B.V. All rights reserved.

562. Highly adherent bioactive glass thin films synthetized by magnetron sputtering at low temperature

Authors: Stan, GE; Pasuk, I; Husanu, MA; Enculescu, I; Pina, S; Lemos, AF; Tulyaganov, DU; El Mabrouk, K; Ferreira, JMF

Published: DEC 2011, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 22, 2710, DOI: 10.1007/s10856-011-4441-1

Thin (380-510 nm) films of a low silica content bioglass with MgO, B2O3, and CaF2 as additives were deposited at low-temperature (150A degrees C) by radio-frequency magnetron sputtering onto titanium substrates. The influence of sputtering conditions on morphology, structure, composition, bonding strength and in vitro bioactivity of sputtered bioglass films was investigated. Excellent pull-out adherence (similar to 73 MPa) was obtained when using a 0.3 Pa argon sputtering pressure (BG-a). The adherence declined (similar to 46 MPa) upon increasing the working pressure to 0.4 Pa (BG-b) or when using a reactive gas mixture (similar to 50 MPa). The SBF tests clearly demonstrated strong biomineralization features for all bioglass sputtered films. The biomineralization rate increased from BG-a to BG-b, and yet more for BG-c. A well-crystallized calcium hydrogen phosphate-like phase was observed after 3 and 15 days of immersion in SBF in all bioglass layers, which transformed monotonously into hydroxyapatite under prolonged SBF immersion. Alkali and alkali-earth salts (NaCl, KCl and CaCO3) were also found at the surface of samples soaked in SBF for 30 days. The study indicated that features such as composition, structure, adherence and bioactivity of bioglass films can be tailored simply by altering the magnetron sputtering working conditions, proving that this less explored technique is a promising alternative for preparing implant-type coatings.

563. Study of X-ray radiation damage in silicon sensors

Authors: Zhang, J; Fretwurst, E; Klanner, R; Perrey, H; Pintilie, I; Poehlsen, T; Schwandt, J

Published: NOV 2011, JOURNAL OF INSTRUMENTATION, 6, DOI: 10.1088/1748-0221/6/11/C11013

The European X-ray Free Electron Laser (XFEL) will deliver 30,000 fully coherent, high brilliance X-ray pulses per second each with a duration below 100 fs. This will allow the recording of diffraction patterns of single complex molecules and the study of ultra-fast processes. Silicon pixel sensors will be used to record the diffraction images. In 3 years of operation the sensors will be exposed to doses of up to 1 GGy of 12 keV X-rays. At this X-ray energy no bulk damage in silicon is expected. However fixed oxide charges in the insulating layer covering the silicon and interface traps at the Si-SiO(2) interface will be introduced by the irradiation and build up over time. We have investigated the microscopic defects in test structures and the macroscopic electrical properties of segmented detectors as a function of the X-ray dose. From the test structures we determine the oxide charge density and the densities of interface traps as a function of dose. We find that both saturate (and even decrease) for doses between 10 and 100 MGy. For segmented sensors the defects introduced by the X-rays increase the full depletion voltage, the surface leakage current and the inter-pixel capacitance. We observe that an electron accumulation layer forms at the Si-SiO(2) interface. Its width increases with dose and decreases with applied bias voltage. Using TCAD simulations with the dose dependent parameters obtained from the test structures, we are able to reproduce the observed results. This allows us to optimize the sensor design for the XFEL requirements. In addition the Si-SiO(2) interface region has been studied with time resolved signals induced by sub-nanosecond 660 nm laser light, which has a penetration of about 3 m m in silicon. Depending on the biasing history, humidity and irradiation dose, losses of either electrons or holes or no charge losses are observed. The relevance of these results for the sensor stability and performance is under investigation.

564. Growth of highly oriented iridium oxide bottom electrode for Pb(Zr,Ti)O-3 thin films using titanium oxide seed layer

Authors: Trupina, L; Miclea, C; Amarande, L; Cioangher, M

Published: NOV 2011, JOURNAL OF MATERIALS SCIENCE, 46, 6834, DOI: 10.1007/s10853-011-5642-1

Due to its low resistivity and excellent thermal stability, IrO2 has attracted attention as an alternative for electrode material in ferroelectric integrated circuit applications. Oriented growth of IrO2 electrode film was investigated with the goal to control the texture of the PZT thin film. IrO2 films were prepared by DC reactive sputtering. PZT film was prepared by RF magnetron sputtering single target deposition method. The whole layer stack was grown onto amorphous thermal oxide of a silicon wafer. The results indicate that IrO2 thin film was preferentially (200) oriented when a TiO2 seeding layer was used. The orientation relationships along the whole PZT(111)/IrO2(200)/TiO2(200)/Ti structure was discussed.

565. Radical modification of the wetting behavior of textiles coated with ZnO thin films and nanoparticles when changing the ambient pressure in the pulsed laser deposition process

Authors: Popescu, AC; Duta, L; Dorcioman, G; Mihailescu, IN; Stan, GE; Pasuk, I; Zgura, I; Beica, T; Enculescu, I; Ianculescu, A; Dumitrescu, I

Published: SEP 15 2011, JOURNAL OF APPLIED PHYSICS, 110, DOI: 10.1063/1.3639297

Cotton/polyester woven fabrics were functionalized with ZnO thin films or nanoparticles by pulsed laser deposition, using a KrF* excimer laser source. Depending on the number of applied laser pulses, well-separated nanoparticles (for 10 pulses) or compact thin films (for 100 pulses) were deposited. The synthesized nanostructures were evaluated morphologically by scanning electron microscopy and atomic force microscopy, physico-chemically by x-ray diffraction and functionally by the contact angle method. By modifying the ambient gas nature and pressure in the deposition chamber, hydrophilic or hydrophobic surfaces were obtained. When using an oxygen flux, both the deposited thin films and nanoparticles were hydrophilic. After deposition in vacuum, the nanoparticles were hydrophobic, but the thin films were super-hydrophobic. This radical modification of wetting behavior was assigned to the differences in microstructure features and surface electrical charging in the two cases. (C) 2011 American Institute of Physics. [doi:10.1063/1.3639297]

566. Lead-free ferroelectric BaTiO3 doped-(Na0.5Bi0.5)TiO3 thin films processed by pulsed laser deposition technique

Authors: Dragoi, C; Cernea, M; Trupina, L

Published: SEP 1 2011, APPLIED SURFACE SCIENCE, 257, 9605, DOI: 10.1016/j.apsusc.2011.06.075

The difficulties in synthesizing phase pure BaTiO3 doped-(Na0.5Bi0.5)TiO3 are known. In this work, we reporting the optimized pulsed laser deposition (PLD) conditions for obtaining pure phase 0.92(Na0.5Bi0.5)TiO3-0.08BaTiO(3), (BNT-BT0.08), thin films. Dielectric, ferroelectric and piezoelectric properties of BNT-BT0.08, thin films deposited by PLD on Pt/TiO2/SiO2/Si substrates are investigated in this paper. Perovskite structure of BNT-BT0.08 thin films with random orientation of nanocrystallites has been obtained by deposition at 600 degrees C. The relative dielectric constant and loss tangent at 100 kHz, of BNT-BT0.08 thin film with 530 nm thickness, were 820 and 0.13, respectively. Ferroelectric hysteresis measurements indicated a remnant polarization value of 22 mu C/cm(2) and a coercive field of 120 kV/cm. The piezoresponse force microscopy (PFM) data showed that most of the grains seem to be constituted of single ferroelectric domain. The as-deposited BNT-BT0.08 thin film is ferroelectric at the nanoscale level and piezoelectric. (C) 2011 Elsevier B.V. All rights reserved.

567. Tailoring the optical properties of Mg (x) Zn1-x O thin films by nitrogen doping

Authors: Epurescu, G; Birjega, R; Galca, AC

Published: SEP 2011, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 104, 893, DOI: 10.1007/s00339-011-6433-x

Thin films of Mg (x) Zn1-x O and Mg (x) Zn1-x O doped with nitrogen were deposited by Radio Frequency plasma beam assisted Pulsed Laser Deposition (RF-PLD) in oxygen or oxygen-nitrogen discharge with different nitrogen/oxygen ratios. A Nd:YAG laser working at a wavelength of 266 nm, having a 10 Hz repetition rate was used for the depositions. The energy density of the incident beam was 3 J/cm(2) and the RF power was set to 100 W for all the samples. X-ray Diffraction (XRD) and Spectroscopic Ellipsometry (SE) were employed to investigate the samples. The degree of crystallinity is fount to decrease with increasing the Mg concentration, while the solubility of Mg in ZnO increases by 30% in the N-doped Mg (x) Zn1-x O thin films grown by RF-PLD. Segregation of MgO phase at a Mg concentration of 30% for Mg (x) Zn1-x O thin film is detected both by XRD and SE. The band gap of the samples increases from 3.37 up to 3.57 eV with increasing the Mg concentration and the nitrogen/oxygen ratio for each Mg concentration. A dependence of the dielectric function (refractive index) on both stoichiometry and degree of crystalinity is also found, the refractive index having values between 1.7 and 2 in visible spectral range.

568. Piezoelectric BNT-BT0.11 thin films processed by sol-gel technique

Authors: Cernea, M; Galca, AC; Cioangher, MC; Dragoi, C; Ioncea, G

Published: SEP 2011, JOURNAL OF MATERIALS SCIENCE, 46, 5627, DOI: 10.1007/s10853-011-5512-x

0.89(Na0.5Bi0.5)TiO3-0.11BaTiO(3), (BNT-BT0.11) thin film was fabricated by sol-gel/spin coating process, on platinized silicon wafer. Perovskite structure with random orientation of crystallites has been obtained at 700 A degrees C. Piezoelectric activity of BNT-BT0.11 thin film was detected using piezoresponse force microscopy (PFM). Effective piezoelectric coefficient d (33eff) of such film, recorded at 5 V applied dc voltage, was similar to 29 pm/V, which is similar to other BNT-BT (x) thin films. The complex refractive index and dielectric function of BNT-BT0.11 thin films were also investigated. The high leakage current density significantly influences the dielectric, ferroelectric, and piezoelectric properties of the BNT-BT0.11 films.

569. Interface controlled photovoltaic effect in epitaxial Pb(Zr,Ti)O-3 films with tetragonal structure

Authors: Pintilie, L; Dragoi, C; Pintilie, I

Published: AUG 15 2011, JOURNAL OF APPLIED PHYSICS, 110, DOI: 10.1063/1.3624738

It is shown that the short-circuit photocurrent measured under illumination in Pb(Zr,Ti)O-3 epitaxial films is strongly dependent on the metal used as the top electrode. The magnitude of the photocurrent varies by more than 2 orders of magnitude from Pt (largest signal) to Al (smallest signal). The differences are for both directions of polarization. The imprint is also dependent on the top metal electrode, with a direct effect on the shape of the spectral distribution. The results support the hypothesis that the origin of the photovoltaic effect in ferroelectric thin films is different from that of the anomalous photovoltaic effect observed in bulk ceramics and single crystals. (C) 2011 American Institute of Physics. [doi:10.1063/1.3624738]

570. The study of the electric and magnetic properties of PbZr0.2Ti0.8O3-BiFeO3 multilayers

Authors: Stancu, V; Dragoi, C; Kuncser, V; Schinteie, G; Trupina, L; Vasile, E; Pintilie, L

Published: JUL 29 2011, THIN SOLID FILMS, 519, 6277, DOI: 10.1016/j.tsf.2011.03.136

The results of the electric and magnetic measurements performed on PbZr0.2Ti0.8O3-BiFeO3 symmetric structures, deposited on Pt/Si wafers, were compared for different number of layers in order to analyse the effect of interfaces over the macroscopic properties. It was found that the shape and magnitude of the capacitance-voltage characteristic, as well as the shape and parameters of the ferroelectric and magnetic hysteresis, depend on the number of interfaces in the intended multilayer structure. A temperature induced gradual transition from a magnetically disordered spin glass like phase of low temperature to an uncompensated antiferromagnetic phase at room temperature takes place in the BiFeO3 films, under low applied magnetic fields. A partial ferromagnetic like order can be obtained at low temperatures by increasing the field. The observed changes in the electric and magnetic behaviour of the systems were related to an increased degree of disorder for electric dipoles and magnetic moments, due to the increased number of layers and crystallization treatments. (C) 2011 Elsevier B.V. All rights reserved.