National Institute Of Materials Physics - Romania

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5781 articles found

1161. TAILORING SP2/SP3 RATIO IN DIAMOND-LIKE CARBON FILMS VIA DEPOSITION PARAMETERS IN A HIGH VOLTAGE ANODIC VACUUM PLASMA

Authors: Badulescu, M; Anghel, A; Surdu-Bob, CC; Logofatu, C; Luculescu, C

Published: 2019, ROMANIAN REPORTS IN PHYSICS, 71, DOI:

Tailoring sp(2)/sp(3) ratio in diamond-like carbon thin films offers new surface engineering solutions for the continuously increasing devices requirements in various fields. We report here the control of sp(2)/sp(3) carbon content using the high voltage anodic plasma in vacuum. Correlation of data obtained by visible Raman Spectroscopy and XPS spectra of our DLC films with deposition parameters showed an increase in sp(3) bonding of about 10% when decreasing the discharge voltage from 600 V to 200 V or increasing the anode-substrate distance from 15 cm to 36 cm.

1162. Comparison between dielectric and pyroelectric properties of PZFNT and BST type ceramics

Authors: Stancu, V; Amarande, L; Botea, M; Iuga, A; Leonat, LN; Tomulescu, AG; Cioangher, M; Balescu, LM; Pintilie, L

Published: 2019, PROCESSING AND APPLICATION OF CERAMICS, 13, 276, DOI: 10.2298/PAC1903269S

Ba0.75Sr0.25TiO3 (BST) and PbZr0.68Fe0.14Nb0.14Ti0.04O3 (PZFNT) ceramic pellets were obtained by ceramic technology and their structural, ferroelectric and pyroelectric properties were investigated. The relative density of BST and PZFNT is about 93% and 90%, respectively, with an average grain size of 102 mu m and 6.45 mu m. Both materials have similar room temperature dielectric constants (similar to 2000), but PZFNT shows higher remnant polarization (similar to 15 mu C/cm(2)) and better pyroelectric properties (similar to 1.69 . 10(-4) C/m(2)K), which recommend it for pyroelectric detectors, infrared radiation- and laser pulse energy-meters.

1163. PHOTO-ELECTRICAL PROPERTIES OF THIN FILMS WITH GE NANOPARTICLES EMBEDDED IN TIO2 MATRIX

Authors: Stavarache, I; Maraloiu, VA

Published: 2019, ROMANIAN REPORTS IN PHYSICS, 71, DOI:

We present photo-electrical properties of thin films formed of Ge nanoparticles in TiO2 correlated with structure and morphology. The films co-deposited on Si using magnetron sputtering were annealed in conventional oven at 550 degrees C. We performed structure investigations by X-ray diffraction, transmission electron microscopy and measured current-voltage characteristics in dark and under illumination at different temperatures. We show that the films are formed of cubic Ge nanoparticles in nanostructured anatase TiO2 matrix. Also, (TiGe)O-2 with rutile structure was observed. The films have high photosensitivity under white light as the ratio between photo- and dark currents (-1 V) is of similar to 10(2).

1164. High performance NIR photosensitive films of Ge nanoparticles in Si3N4

Authors: Stavarache, I; Prepelita, P; Lalau, I; Cojocaru, O; Teodorescu, VS; Ciurea, ML

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 228, DOI:

Films of amorphous Ge nanoparticles in Si3N4 on heated Si and quartz substrates at 300 degrees C were obtained by co-sputtering Ge, and Si3N4. The films structure and photo-electrical behaviour were studied through transmission electron microscopy and, current voltage and spectral photo-current investigations, respectively. The spectral photo-current were correlated with results obtained from transmission electron microscopy. Under illumination the current present a high increase with about one order of magnitude compared with the dark one. The photo-current spectra show a widening in near infrared to 0.97eV. Internal quantum efficiency values for -1V and 0V were determined.

1165. Controlling SWIR photosensitivity limit by composition engineering: from Ge to GeSi nanocrystals embedded in TiO2

Authors: Dascalescu, I; Cojocaru, O; Lalau, I; Palade, C; Slav, A; Lepadatu, AM; Lazanu, S; Stoica, T; Ciurea, ML

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 40, DOI:

The VIS-SWIR photosensing properties of Ge and GeSi NCs embedded in TiO2 films are investigated. For this, we deposit GeTiO2 and GeSiTiO2 films, respectively by magnetron sputtering and then we perform rapid thermal annealing (RTA) for Ge NCs and GeSi NCs formation, respectively. Raman studies and spectral photocurrent measurements were carried out. Ge NCs formation is evidenced in the Raman spectrum of GeTiO2 film annealed at 550 degrees C. The photocurrent spectra measured on the Ge NCs-TiO2 film present four peaks separated by deconvolution. The broad peaks at similar to 700, 890, 1010 nm are due to photo-effects in the Ge NCs-TiO2 film. More than that, the photocurrent increases exponentially with the increase of bias voltage. The cut-off wavelength is similar to 1240 nm. We achieve the extension of the photosensitivity limit to similar to 1310 nm in GeSi NCs-TiO2 films (800 degrees C RTA).

1166. Frequency selective surfaces with hexagonal elements for millimeter waves applications

Authors: Banciu, MG; Geambasu, DC; Nedelcu, L; Trupina, L

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 64, DOI:

Numerical investigations on a frequency selective surface using metalized strips deposited on high resistive silicon in a millimeter waves are presented in this paper. High resistivity Si substrate was chosen due to the very good transparence in millimeter waves. For simulations, normal incidence of millimeter waves alongside Floquet modes and ports are considered. Dependence of the frequency response with the geometrical parameters of the unit cell is discussed.

1167. Properties of textile and leather materials treated with new hybrid SiO2/TiO2/poly(2,2 '-bithiophene) nanocomposites

Authors: Chirila, L; Gaidau, C; Stroe, M; Baibarac, M; Stanca, M; Radulescu, DM; Radulescu, DE; Alexe, CA

Published: 2019, , DOI: 10.35530/IT.070.03.1634

The aim of this study was to investigate the influence of new hybrid composites of TiO2 or SiO2 nanoparticles with poly(2,2'-bithiophene) on 50% cotton/50% polyester fabric and sheep skin leather surface properties. The dispersion-based newly made nanocomposites were analyzed to determine conductivity, particle size, polydispersity and Zeta potential. The finished textile and leather materials were characterized in terms of functionalization treatments performance by: surface resistivity, water contact behaviour, physical-mechanical characteristics and photocatalytic properties. SEM analysis was used to investigate the distribution of nanoparticles on the textile and leather materials surface. Textile materials treated with SiO2/poly(2,2'-bithiophene) nanocomposite with concentration 98 wt% nanoparticles of SiO2 and leather treated with poly SiO2/poly(2,2'-bithiophene) nanocomposite with concentration of 95 wt% nanoparticles of SiO2 showed lower resistivity values, confirming the conductive properties of silica. The higher photodegradation efficiency of functionalized materials has been obtained for textile material treated with poly TiO2/(2,2'-bithiophene) with concentration of 95 wt% nanoparticles of TiO2 and for leather material treated with TiO2/poly(2,2'-bithiophene) with concentration of 98 wt% nanoparticles of TiO2, respectively.

1168. DENSITY OF ADSORBED SURFACE SPECIES FOR CYANOPHENYL ALKYL BENZOATES CONFINED TO AEROSIL A380: DEVELOPMENT OF THE EVALUATING ALGORITHM FOR ATTACHMENT BY TWO TYPES OF BONDS

Authors: Frunza, S; Frunza, L; Ganea, CP; Zgura, I; Schonhals, A

Published: 2019, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS, 81, 236, DOI:

We found previously how to estimate the density of the adsorbed surface species in the case of the molecules interacting to the oxide support surface by one type of bond. Here this algorithm is developed for the case of the molecules which can be bonded to the support surface by two types of bonds. The adsorption assumptions are similar to those considered in the case of only one type of bond. The calculation is exemplified for some composites of cyanophenyl alkylbenzoates (CPnBs) (n is the number of carbon atoms in the alkyl chain) interacting with Aerosil A380. The interaction takes place by hydrogen bonding between the -OH groups or the support and the functional groups of the CPnB molecules. The estimated values of the total surface density of CPnBs agree well with those found for the composites containing related but simpler molecules.

1169. Capatanii/Parang Mountains: Polovragi Cave-Oltetului Gorge Karst Area

Authors: Ponta, GML; Aldica, GV; Dumitru, R

Published: 2019, CAVE AND KARST SYSTEMS OF ROMANIA, 91, DOI: 10.1007/978-3-319-90747-5_12

The Polovragi Cave-Oltetului Gorge karst area is about 3 km(2) in size and is traverse by the Oltet River through a spectacular narrow gorge, which represents the natural boundary between Parang Mountains to the west and Capatanii Mountains in the east. These mountains are part of the Southern Carpathian. Focul Viu Caving Club surveyed the Polovragi Cave between 1975 and 1985. In parallel with the survey activities in the main cave developed on the first level, several smaller caves were identified on both sides of the Oltetului Gorge. These caves are located on the second and third levels, which are interrelated with different peneplanation events that occurred in the Carpathians. In 2000, Focul Viu began working in the cave again, replacing gates, removing trash, digging to open new passages, and performing underwater explorations. By the end of 2011, new passages were found in the Hope Chamber and Costin Gallery, extending the total length of the cave to 10,793 and 92 m in vertical range. The Polovragi Cave along with two other smaller caves is presented in this chapter. The Polovragi Cave is the third longest cave in the Southern Carpathians and the eleventh in Romania. One of the smaller caves hosts an important bat colony, and the other one, with 800 m of passages, hosts Ursus spelaeus bones and deposits of saltpeter. The Bones Cave (Pestera cu Oase) located on the western side of the gorge (opposite side of Polovragi Cave) at a higher elevation is an old meander of the Oltet River.

1170. STRUCTURAL, DIELECTRIC AND PYROELECTRIC PROPERTIES OF Nb AND Fe DOPED PZT CERAMICS

Authors: Stancu, V; Amarande, L; Botea, M; Cioangher, M; Tomulescu, A; Iuga, A; Pintilie, L

Published: JAN-MAR 2019, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 14, 230, DOI:

Lead zirconate titanate doped with iron and niobium (PZFNT) was prepared by conventional processing technique, solid state synthesis method. The influence of dopants on the microstructure, ferroelectric and pyroelectric properties was investigated. XRD data reveals a perovskite structure near to the lead zirconate phase. The relative density of PZFNT is approximate 90%, with average grains size of 6.45 mu m.