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The effect of argon plasma treatment on the permeation barrier properties of si...
Majee, Subimal; Cerqueira, M. F.; Tondelier, D.; Geffroy, B.; Bonnassieux, Y.; Alpuim, P.; Bourée, J. E.In this work we produce and study silicon nitride (SiNx) thin films deposited by Hot Wire Chemical Vapor Depo- sition (HW-CVD) to be used as encapsulation barriers for flexible organic photovoltaic cells fabricated on poly- ethylene terephthalate (PET) substrates in order to increase their shelf lifetime. We report on the results of SiNx double-layers and on the equivalent double-layer stack where an Ar-plasma ...
Study on excimer laser irradiation for controlled dehydrogenation and crystalli...
Gontad, F.; Filonovich, Sergey; Cerqueira, M. F.; Alpuim, P.; Chiussi, StefanoWe report on the excimer laser annealing (ELA) induced temperature gradients, allowing controlled crystal-lization and dehydrogenation of boron-doped a-Si:H/nc-Si:H multilayers. Depth of the dehydrogenation and crystallization process has been studied numerically and experimentally, showing that temperatures below the monohydride decomposition can be used and that significant changes of the doping profile can be ...
Nano-ilmenite FeTiO3 : synthesis and characterization
Raghavender, A. T.; Hoa Hong, Nguyen; Lee, Kyu Joon; Jung, Myung-Hwa; Skoko, Z.; Vasilevskiy, Mikhail; Cerqueira, M. F.; Samantilleke, A. P.In general, ilmenite FeTiO3 is synthesized by solid-state reaction at very high pressure and high temperature. Synthesis of FeTiO3 is not an easy task as the Fe2+ ions are not stable. Therefore, it is really challenging to prepare this material. In this work nano-ilmenite FeTiO3 was synthesized by the sol-gel method. Structural, optical and magnetic characterizations were performed. The bandgap of FeTiO3 was de...
Resonant raman scattering in ZnO : Mn and ZnO: Mn : Al thin films grown by RF s...
Cerqueira, M. F.; Vasilevskiy, Mikhail; Oliveira, F.; Rolo, Anabela G.; Viseu, T. M. R.; Campos, J. Ayres de; Alves, E.; Correia, RosárioRaman spectroscopy results obtained under visible (non-resonant) and UV (resonant) excitation for nanocrystalline ZnO, ZnO:Mn and ZnO:Mn:Al thin films grown by radio frequency magnetron sputtering are presented and compared. The origin of the multiple longitudinal optical (LO) phonon Raman peaks, strongly enhanced under resonance conditions, and the effects of the dopants on them are discussed in the framework ...
High-rate deposition of nano-crystalline silicon thin films on plastics
Marins, Emílio Sérgio; Guduru, Virendra; Ribeiro, Miguel; Cerqueira, M. F.; Bouattour, Ali; Alpuim, P.Nanocrystalline silicon (nc-Si:H) is commonly used in the bottom cell of tandem solar cells. With an indirect bandgap, nc-Si:H requires thicker (∼1 µm) films for efficient light harvesting than amorphous Si (a-Si:H) does. Therefore, thin-film high deposition rates are crucial for further cost reduction of highly efficient a–Si:H based photovoltaic technology. Plastic substrates allow for further cost reduction ...
Room temperature paramagnetism of ZnO:Mn films grown by RF-sputtering
Oliveira, Filipe André; Cerqueira, M. F.; Vasilevskiy, Mikhail; Viseu, T. M. R.; Campos, J. Ayres de; Rolo, Anabela G.; Martins, J. S.; Sobolev, N. A.ZnO:Mn transparent thin films (thickness b1 μm) with the Mn contents ranging from 1.8 to 3.25 at.% were grown by RF magnetron co-sputtering. The films are nanocrystalline, with wurtzite-structure grains of a typical size of 20 nm and with a preferential orientation of the c-axis perpendicular to the surface. According to the Raman spectroscopy data, Mn mostly substitutes Zn in the lattice sites. In spite of the...
Raman study of doped-ZnO thin films
Cerqueira, M. F.; Rolo, Anabela G.; Viseu, T. M. R.; Campos, J. Ayres de; Arôso, T. de Lacerda; Oliveira, F.; Vasilevskiy, Mikhail; Alves, E.A Raman spectroscopy study of doped versus undoped ZnO layers is presented. The layers were grown by RF magnetron sputtering and the doping with Al, Sb and Mn was achieved by ion implantation with subsequent annealing. First-order Raman response measured under λ=488 nm excitation is discussed. It is shown that doping with any of the impurities used in this work produces a strong enhancement of the longitudinal ...
Electrical and raman scattering studies of ZnO:P and ZnO:Sb thin films
Campos, J. Ayres de; Viseu, T. M. R.; Barradas, N. P.; Alves, E.; Lacerda-Arôso, T. de Lacerda; Cerqueira, M. F.; Rolo, Anabela G.A study on the structure, electrical and optical properties of ZnO thin films produced by r.f. magnetron sputtering and implanted either with phosphorous (P) or antimony (Sb) is reported in this work. Raman spectroscopy, X-ray diffraction, optical transmittance and Hall effect measurements have been employed to characterize the samples. X-ray diffraction and Raman scattering patterns confirm that, after a 500ºC...
Crystal size and crystalline volume fraction effects on the Erbium emission of ...
Cerqueira, M. F.; Stepikhova, M.; Kozanecki, A.; Andrês, G.; Alves, E.Erbium-doped low-dimensional Si films with different microstructures were grown by reactive magnetron sputtering on glass substrates by varying the deposition parameters. Their structure and chemical composition were studied by micro-Raman and Rutherford backscattering spectrometry, respectively. In this contribution the Erbium emission is studied as a function of nanocrystalline fraction and average crystal si...
Effect of grain size and hydrogen passivation on the electrical properties of n...
Cerqueira, M. F.; Semikina, T. V.; Baidus, N. V.; Alves, E.The properties of mixed-phase (nanocrystalline/amorphous) silicon layers produced by reactive RF-sputtering are described. The chemical composition and nanostructure [i.e. nanocrystal (NC) size and volume fraction] of the films were studied by Rutherford backscattering spectroscopy (RBS) and micro-Raman spectroscopy, respectively. Samples with different fractions of the nanocrystalline phase and NC mean size we...
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