National Institute Of Materials Physics - Romania

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5714 articles found

1301. Conductivity losses in ferroelectric phase of TGS

Authors: Marinel, D; Alexandru, HV; Ganea, CP

Published: NOV-DEC 2018, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 20, 681, DOI:

Triglycine sulphate (TGS) is a crystal having a typical second order ferroelectric transition and the Curie point around 49 degrees C. It is quite easy to grow and to analyse its properties. Our TGS crystals were grown by slow solvent evaporation in paraelectric phase, around 54 degrees C, where no mechanical tensions due to ferroelectric domains were present. Dielectric properies of TGS crystals were continuously measured at a pace of 0.6 degrees C/min, starting from 65 degrees C, crossing down the Curie point until zero Celsius, on the frequency range 1 divided by 10(7) Hz. The two component of permittivity were measured and the parameters vs. temperature were estimated and analysed.

1302. ESR Study of Irradiated Polysaccharides ESR investigation of gamma irradiated pectin

Authors: Slave, RM; Grecu, MN; Grecu, VV

Published: 2018, 4TH INTERNATIONAL SCIENTIFIC CONFERENCE SEA-CONF 2018, 172, DOI: 10.1088/1755-1315/172/1/012003

Polysaccharides irradiation is usually used for their decontamination of fungi, pathogenic bacteria, toxigenic molds, parasitic organisms. ESR studies are performed just to evidence their irradiation. Therefore the accent is put on radical stability in time and ESR signal intensity dependence on irradiation dose. Less attention is given to radical nature and their dependence on plant nature. In this report a study of gamma irradiated pectin is given. Dose dependence of double integrated ESR signal is analyzed in terms of a recombination reaction during the radiation period. Radical stability dependence on water content is put in evidence.

1303. Enhanced photocurrent in GeSi NCs / TiO2 multilayers

Authors: Palade, C; Slav, A; Cojocaru, O; Teodorescu, VS; Lazanu, S; Stoica, T; Sultan, MT; Svavarsson, HG; Ciurea, ML

Published: 2018, , DOI:

GeSi NCs / TiO2 multilayers with enhanced photocurrent properties were prepared and studied. Multilayers of TiO2 /(GeSi/TiO2)x2 /Si-p were deposited by magnetron sputtering and annealed by RTA at 700 degrees C for GeSi NCs formation. A post-annealing hydrogenation in plasma was performed on multilayers for healing of defects acting as traps and/or recombination centers and consequently producing the photocurrent enhancement. We studied the electrical and photoconductive properties of multilayers annealed by RTA and post-annealing hydrogenated. The current - temperature dependence reveals the conduction mechanisms in GeSi NCs / TiO2 multilayers RTA annealed, i.e. thermal activation of carriers to extended states (0.31 eV activation energy), the electron tunneling mechanism to nearest neighbors (T-1/2 behavior) and Mott variable range hopping (T-1/4 dependence). The photocurrent spectra made on multilayers structures hydrogenated for 10, 20 and 30 min evidence the photocurrent increasing up to 50%, showing that the hydrogenation is a suitable treatment for enhancing photocurrent. All photocurrent spectra present a dominant maximum (920 nm) and two shoulders (similar to 770 and similar to 1060 nm).

1304. Millimeter wave and Terahertz investigations on some dielectric materials

Authors: Banciu, MG; Furuya, T; Geambasu, DC; Nedelcu, L; Pantelica, D; Dracea, MD; Ionescu, P; Iuga, A; Chirila, C; Hrib, L; Trupina, L; Tani, M

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 290, DOI:

Investigations of barium strontium titanate (BST) layers deposited on MgO and Si substrates are presented. Since the Sr content determines the dielectric and optical properties of the BST layers at room temperature, accurate compositional analysis was performed by using Rutherford Backscattering technique at 3.041 Mev.

1305. ANALYSIS of Pdge-BASED CONTACT on N-Gasb

Authors: Ghita, RV; Negrila, CC; Predoi, D; Trusca, R

Published: 2018, 7TH INTERNATIONAL CONFERENCE ON STRUCTURAL ANALYSIS OF ADVANCED MATERIALS (ICSAAM 2017), 1932, DOI: 10.1063/1.5024167

Pd-Ge based ohmic contacts on III-V semiconductor e.g.Pd-Ge on n-GaAs are viewed as a viable alternative to low contact resistance metallization. As it was remarked [11, together with the device dimensions decrease, the AuGeNi metallization system becomes inadequate for shallow-junction devices. This characteristic is related to the formation of a low melting point beta- AuGa phase that leads to a poor contact thermal stability. Gallium Antimonide is anIII-V semiconductor compound that can be used in a photovoltaic convertor of GaAs/GaSb tandem stack With a predicted efficiency of 30%. Reduced series resistance on GaSb cells can be achieved by the improving of contact metallization properties. The present study is dedicated to the preparation conditions and structural analyzing of PdGe based contacts on n-GaSb, namely: Pd/Au/Ge. There are presented the depth profiling for PdGe metallization obtained from XPS measurements, and morphologic studies arisen from SEM technique and AFM technique.

1306. AlN/Si based SAW resonators for very high sensitivity temperature sensors

Authors: Nicoloiu, A; Muller, A; Zdru, I; Vasilache, D; Stan, GE; Nastase, C; Dumitru, V; Dinescu, A

Published: 2018, 2018 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS), DOI:

In the current work we present AlN/Si based Surface Acoustic Wave (SAW) devices exploited as high sensitivity temperature sensors. The experimental results show that the resonance frequency varies between 3.2 and 5.5 GHz, depending on the finger/Interdigit spacing width and metal thickness. The temperature measurements were performed between -250 degrees C and +150 degrees C in a cryostat. The sensitivities were investigated between 24-150 degrees C and the values were compared to the results obtained for similar GaN/Si based SAW structures.

1307. GeSi nanocrystals in SiO2 matrix with extended photoresponse in near infrared

Authors: Stavarache, I; Nedelcu, L; Teodorescu, VS; Maraloiu, VA; Dascalescu, I; Ciurea, ML

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 256, DOI:

The films of SiGe nanocrystals in SiO2 on Si substrate were obtained by co-sputtering Si, Ge, and SiO2 followed by rapid thermal annealing. The films structure and morphology together with electrical and photoelectrical properties were studied by x-ray diffraction, transmission electron microscopy, current - voltage and spectral photocurrent measurements. The photocurrent spectra at 300, 200 and 100 K were correlated with results obtained from X-ray diffractograms and transmission electron microscopy. The photocurrent spectra show an extension in near infrared due to the enriching SiGe nanocrystals in Ge.

1308. The Cu- and Zn-complex-catalyzed methanolysis of the chemical warfare nerve agents soman, sarin, and VX

Authors: Petrea, N; Petre, R; Pretorian, A; Toader, C; Somoghi, V; Neatu, F; Florea, M; Neatu, S

Published: MAR-APR 2018, COMPTES RENDUS CHIMIE, 21, 345, DOI: 10.1016/j.crci.2017.08.006

The catalytic methanolysis of the chemical warfare nerve agents soman, sarin, and VX was investigated by using Cu or Zn complexes. Although VX withstood decontamination, the decomposition yield being around 96%, the soman and sarin deposited on different surfaces were almost fully destroyed under ambient conditions. The catalytic tests performed on a wide range of contaminated surfaces confirm the activity of the investigated catalytic systems, these complexes being suitable, from an economical point of view, for use in the formulation of a possible decomposition kit with military or civilian applicability. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

1309. OPTICAL COATINGS FOR ELI EXPERIMENTS PREPARED BY LASER ABLATION

Authors: Bercea, A; Filipescu, M; Moldovan, A; Brajnicov, S; Colceag, D; Ion, V; Nistor, LC; Zorila, A; Dinescu, M

Published: 2018, ROMANIAN JOURNAL OF PHYSICS, 63, DOI:

Dielectric materials (HfO2, A1(2)O(3), SiO2 and Ta2O5) processed as thin films have been studied extensively for applications in microelectronics, biology, medicine, etc. In the last decade, antireflection coatings based on these types of materials have received considerable attention for applications in the field of high power laser optics. In this paper we report on multi-layers from materials with low and high refractive indices deposited on quartz substrates by laser ablation. Damage tests performed with a Ti-Sapphire laser (775 nm wavelength, 220 fs pulse duration) evidenced higher threshold values for hafnia based heterostructures than for the others heterostructures.

1310. Spectroscopic Characterisation of Multiferroic Interfaces

Authors: Husanu, MA; Vaz, CAF

Published: 2018, SPECTROSCOPY OF COMPLEX OXIDE INTERFACES: PHOTOEMISSION AND RELATED SPECTROSCOPIES, 266, 281, DOI: 10.1007/978-3-319-74989-1_10

In this chapter we discuss the capabilities of X-ray photoemission and absorption spectroscopies for the investigation of the electronic, magnetic and electric properties of multiferroic materials and heterostructures. As complementary techniques providing element selective information on both occupied and empty states, their combination delivers a comprehensive picture of the chemical state of individual species, magnetic moments, bulk and surface band structure, and local atomic environment at the interface between dissimilar materials. By directly probing the electronic structure at the atomic level, unique insights can be learned about the mechanisms responsible for the magnetoelectric couplings in this fascinating class of materials.