Pereira, L.a, Águas Martins Vilarinho Fortunato Martins H. a R. M. "
Polycrystalline silicon obtained by metal induced crystallization using different metals."
Thin Solid Films. 451-452 (2004): 334-339.
AbstractThe aim of this paper is to study the role of different metals (aluminium, molybdenum, nickel and titanium) in inducing crystallization in films produced by LPCVD at high and low temperature processes and to compare the structural, morphological, optical and electrical properties of the various films produced. This work envisages the use of the most suitable conditions that lead to the production of films for optoelectronic applications such as solar cells. © 2003 Elsevier B.V. All rights reserved.
Pereira, L.a, Martins Schell Fortunato Martins R. M. S. b. "
Nickel-assisted metal-induced crystallization of silicon: Effect of native silicon oxide layer."
Thin Solid Films. 511-512 (2006): 275-279.
AbstractThis work focuses on the role of the native oxide layer (SiO2) on the nickel (Ni)-assisted crystallization of amorphous silicon (a-Si). In some samples, the native oxide was removed using a HF-diluted solution before Ni layers with 0.5 nm be deposited on a-Si. The results show that the presence of a thin SiO2 layer of about 3 nm between the a-Si and the Ni delays the crystallization process. Ellipsometry data show that, after annealing for 5 h at 500 °C, the HF-cleaned sample presents a crystalline fraction of 88%, while the one with the native oxide has only 35%. This difference disappears after 20 h where both samples present similar crystalline fraction. These facts are also reflected on the film's electrical properties, where the activation energy for samples annealed for 5 h rises from 0.42 eV to 0.55 eV, when the oxide layer is removed. After 20 h and 30 h, the activation energy is around 0.55 eV for both kinds of samples, meaning that films with similar electrical properties are now obtained. However, the XRD data suggest the presence of some structural differences attributed to slight differences on the crystallization process. © 2005 Elsevier B.V. All rights reserved.
Pereira, L.a, Brida Fortunato Ferreira Águas Silva Costa Teixeira Martins D. a E. a. "
a-Si:H interface optimisation for thin film position sensitive detectors produced on polymeric substrates."
Journal of Non-Crystalline Solids. 299-302 (2002): 1289-1294.
AbstractIn this paper we present results concerning the optimisation of the electronic and mechanical properties presented by amorphous silicon (a-Si:H) thin films produced on polyimide (Kapton® VN) substrates with different thicknesses (25, 50 and 75 μm) by the plasma enhanced chemical vapour deposition (PECVD) technique. The purpose of this study is to obtain a low defect density as well as low residual stresses (specially at the interface) in order to provide good performances for large area (10 mm wide by 80 mm long) flexible position sensitive detectors. The electrical and optical properties presented by the films will be correlated to the sensor characteristics. The properties of samples have been measured by dark/photoconductivity, constant photocurrent measurements (CPM) and the results have been compared with films deposited on Corning 7059 glass substrates during the same run deposition. The residual stresses were measured using an active optical triangulation and angle resolved scattering. The preliminary results indicate that the thinner polymeric substrate with 25 μm presents the highest density of states, which is associated to the residual stresses and strains associated within the film. © 2002 Elsevier Science B.V. All rights reserved.