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331. Enhanced photoconductivity of SiGe-trilayer stack by retrenching annealing conditions
Authors: Sultan, MT; Gudmundsson, JT; Manolescu, A; Ciurea, ML; Palade, C; Maraloiu, AV; Svavarsson, HG

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 64, DOI:

We studied the effect of short term furnace annealing over the photoconductive properties of tristacked layer i.e. TiO2/(SiGe/TiO2)(3). The structure was prepared by depositing alternate layers of TiO2 and SiGe films, using direct-current magnetron sputtering technique. A transmission electron microscopy and grazing incidence spectroscopy was used to analyze the morphology of the structure. Photoconductive properties were studied by measuring photocurrent spectra at different applied voltages and temperatures. Tristack layers were obtained with 5-10 nm SiGe nanocrystals (NCs) by annealing at 600 degrees C for 5 min. No sign of SiO2 formation was found inside stacked layers. A maximum in the photocurrent spectra was observed at 994 nm at 300 K but it red-shifted gradually to 1045 nm with decrease in temperature to 100 K. This transition in peak maxima is attributed to SiGe NCs, due to lattice vibration and to contribution of non-radiative recombination at low temperatures.
332. 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, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 76, 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).
333. CHARACTERIZATION OF SURFACE AND INTERFACE OF Fe-C STEEL UNDER ELECTROLYTIC GALVANIZATION
Authors: Bibicu, I; Bulea, C; Diamandescu, L; Rus, V; Popescu, T; Mercioniu, I

Published: JUL-SEP 2018, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 19, 430, DOI:

Low carbon Fe-C steel surface has been studied before and after electrolytic galvanization. The corrosion products formed under atmospheric conditions on the Fe-C steel were identified and characterised by X-ray diffraction (XRD), transmission Mossbauer spectroscopy, conversion electron Mossbauer spectroscopy (CEMS), and conversion X-ray Mossbauer spectroscopy (CXMS). In decreasing order of abundance the found corrosion phases were magnetite, hematite, and goethite. After the surface preparation, an electrolytic galvanization process was applied. A magnetic anisotropy was evidenced after preparation, in the superficial layer of around 250 nm thickness. Scanning electron microscopy (SEM) analyses evidenced the formation of a uniform thin Zn film of 8 mu m at the surface of steel. No other Fe-Zn phases were identified at the steel-Zn interface.
334. 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).
335. 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.
336. Local configurations and atomic intermixing in as-quenched and annealed Fe1-xCrx and Fe1-xMox ribbons
Authors: Stanciu, AE; Greculeasa, SG; Bartha, C; Schinteie, G; Palade, P; Kuncser, A; Leca, A; Filoti, G; Birsan, A; Crisan, O; Kuncser, V

Published: 2018, PHILOSOPHICAL MAGAZINE, 98, 1067, DOI: 10.1080/14786435.2018.1425556

Local atomic configuration, phase composition and atomic intermixing in Fe-rich Fe1-xCrx and Fe1-xMox ribbons (x = 0.05, 0.10, 0.15), of potential interest for high-temperature applications and nuclear devices, are investigated in this study in relation to specific processing and annealing routes. The Fe-based thin ribbons have been prepared by induction melting, followed by melt spinning and further annealed in He at temperatures up to 1250 degrees C. The complex structural, compositional and atomic configuration characterisation has been performed by means of X-ray diffraction (XRD), transmission Mossbauer spectroscopy and differential scanning calorimetry (TG-DSC). The XRD analysis indicates the formation of the desired solid solutions with body-centred cubic (bcc) structure in the as-quenched state. The Mossbauer spectroscopy results have been analysed in terms of the two-shell model. The distribution of Cr/Mo atoms in the first two coordination spheres is not homogeneous, especially after annealing, as supported by the short-range order parameters. In addition, high-temperature annealing treatments give rise to oxidation of Fe (to haematite, maghemite and magnetite) at the surface of the ribbons. Fe1-xCrx alloys are structurally more stable than the Mo counterpart under annealing at 700 degrees C. Annealing at 1250 degrees C in He enhances drastically the Cr clustering around Fe nuclei.
337. Limits and Particularities of the Synthesis of Ba1-xCaxTiO3 for Piezoelectric Applications, by Topochemical Conversion from Molten Salt Solutions
Authors: Vlaicu, ID; Maraloiu, AV; Ghica, D; Mercioniu, IF; Stefan, M; Vlaicu, AM; Negrea, RF; Kuncser, AC; Bulat, S; Krzmanc, MM; Ciobanu, R; Plopa, O

Published: 2018, 2018 INTERNATIONAL CONFERENCE AND EXPOSITION ON ELECTRICAL AND POWER ENGINEERING (EPE), 1050, DOI:

Because of the unique properties of the ferroelectric perovskite particles with a well-defined anisotropic form like shape-and size dependent at low dimensions they have all the attention of the scientific world. Extensive morphostructural techniques will be used to characterize the piezoelectric material.
338. The effect of H-2/Ar plasma treatment over photoconductivity of SiGe nanoparticles sandwiched between silicon oxide matrix
Authors: Sultan, MT; Gudmundsson, JT; Manolescu, A; Ciurea, ML; Svavarsson, HG

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 260, DOI:

The effect of room temperature hydrogen plasma treatment on the photoconductive properties of the SiO2 matrix containing SiGe nanoparticles is investigated. A considerable increase in photocurrent intensity is observed after plasma treatment. The increase is partly attributed to neutralization of dangling bonds around the nanoparticles and partly to passivation of non-radiative centers and defects in the matrix and at the nanoparticles-matrix interfaces.
339. MOS DOSIMETER BASED ON Ge NANOCRYSTALS IN HfO2
Authors: Palade, C; Slav, A; Lepadatu, AM; Stavarache, I; Dascalescu, I; Cojocaru, O; Stoica, T; Ciurea, ML; Lazanu, S

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 90, DOI:

Trilayer MOS capacitors gate HfO2 / floating gate of Ge nanocrystals in HfO2 / tunnel HfO2 / Si substrate were prepared in the aim to be used for the detection of ionizing radiation. Magnetron sputtering and rapid thermal annealing were used for their fabrication. Capacitance-voltage measurements showed that Ge nanocrystals are the most important charge storage centres in our structure. The possibility to use these trilayer MOS capacitors as dosimeters was investigated, and the sensitivity to alpha particle irradiation was extracted.
340. Origin and chemical composition of the amorphous material from the intergrain pores of self-assembled cubic ZnS:Mn nanocrystals
Authors: Stefan, M; Vlaicu, ID; Nistor, LC; Ghica, D; Nistor, SV

Published: DEC 31 2017, APPLIED SURFACE SCIENCE, 426, 350, DOI: 10.1016/j.apsusc.2017.07.172

We have shown in previous investigations that the low temperature collective magnetism observed in mesoporous cubic ZnS:Mn nanocrystalline powders prepared by colloidal synthesis, with nominal doping concentrations above 0.2 at.%, is due to the formation of Mn2+ clusters with distributed antifer romagnetic coupling localized in an amorphous phase found between the cubic ZnS:Mn nanocrystals. Here we investigate the composition, origin and thermal annealing behavior of this amorphous phase in such a mesoporous ZnS:Mn sample doped with 5 at.% Mn nominal concentration. Correlated analytical transmission electron microscopy, multifrequency electron paramagnetic resonance and Fourier transform infrared spectroscopy data show that the amorphous nanomaterial consists of unreacted precursor hydrated zinc and manganese acetates trapped inside the pores and on the surface of the cubic ZnS nanocrystals. The decomposition of the acetates under isochronal annealing up to 270 degrees C, where the mesoporous structure is still preserved, lead to changes in the nature and strength of the magnetic inter actions between the aggregated Mn2+ ions. These results strongly suggest the possibility to modulate the magnetic properties of such transition metal ions doped II-VI mesoporous structures by varying the synthesis conditions and/or by post-synthesis thermochemical treatments. (C) 2017 Elsevier B.V. All rights reserved.

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