B. P. Falcão

B. P. Falcão
University of Aveiro | UA · CICECO - Aveiro Institute of Materials

Doctor of Engineering

About

25
Publications
5,455
Reads
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368
Citations
Citations since 2017
15 Research Items
282 Citations
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201720182019202020212022202301020304050
201720182019202020212022202301020304050

Publications

Publications (25)
Article
Full-text available
We report an investigation on the morphological, structural, and optical properties of large size wurtzite GaAs nanowires, low doped with Mg, grown on GaAs(111)B and Si(111) substrates. A higher density of vertical nanowires was observed when grown upon GaAs(111)B. Very thin zinc-blende segments are observed along the axis of the nanowires with a s...
Article
Until this day, the most efficient Cu(In,Ga)Se2 thin film solar cells have been prepared using a rather complex growth process often referred to as three-stage or multistage. This family of processes is mainly characterized by a first step deposited with only In, Ga and Se flux to form a first layer. Cu is added in a second step until the film beco...
Article
Raman spectroscopy is widely used to study bulk and nanomaterials, where information is frequently obtained from spectral line positions and intensities. In this study, we monitored the Raman spectrum of ensembles of semiconductor nanocrystals (NCs) as a function of optical excitation intensity (optical excitation experiments). We observe that in N...
Article
The effects of anisotropy and splitting of the phonon dispersions in the Raman spectrum of nanocrystals are investigated. We describe the different branches of the optical phonon dispersion curves along each high-symmetry direction by fitting a simple empirical model to experimental data. These curves are then used to calculate the Raman spectrum i...
Article
The investigation of surface-induced lattice-strain effects in free-standing silicon nanocrystals (Si NCs) is fundamental in view of the materialization of nanosilicon-based technologies that exploit the unique properties of silicon at the nanoscale. In this work, a comprehensive investigation in free-standing Si NCs is performed, aimed at unveilin...
Article
Full-text available
In the present work, we have fabricated silver nanoprism (AgNPrs)/silicon nanoparticle (SiNPs) hybrid arrays for highly sensitive detection of biomolecules via surface-enhanced Raman spectroscopy (SERS) technique. SiNPs having 7 to 37 nm in size and with phosphorous doping varying from 1 × 1019 to 1 × 1020 cm−3 were synthesized in nonthermal plasma...
Article
Zinc oxide (ZnO) nanostructures have been widely used in biosensor applications. However, little attention has been given to the interaction of ZnO structures with physiological buffer solutions. In the present work, it is shown that the use of buffers containing phosphate ions leads to the modification of the ZnO tetrapodal micro/nanostructures wh...
Article
Full-text available
Native defects and unintentional contaminations during growth can strongly influence the optical properties of semiconductors and their applications. The tailoring of these optical properties requires a deep understanding of the role of defects and hence contributes to the improvement of the crystal quality of the epitaxially grown active layer in...
Article
The mechanisms of recombination of photo-generated charge carriers and the origin of luminescence in silicon nanocrystals, quantum dots or nanoparticles (Si-NPs) are essential for the application of these materials in future nano-optoelectronics. In the last two decades, these issues have been lively debated in the literature, with different invest...
Article
The origin of the light emission from nanosilicon systems such as crystalline silicon nanoparticles (Si-NPs) has been an intensively debated issue, with seemingly contradicting literature results pointing to different mechanisms. Here, the origin of the photoluminescence (PL) from application-grade Si-SiO2 core-shell nanoparticles with different si...
Article
Depth bandgap profiles via a [Ga]/([Ga]+[In]) variation in the Cu(In,Ga)Se 2 (CIGS) absorber layer have been implemented as a strategy to enhance the performance of CIGS solar cells. Since the [Ga]/([Ga]+[In]) determines to a large extent the position of the conduction band minimum, different Ga-profiles lead to different electronic energy levels s...
Article
Solution-processed thin films of crystalline silicon nanoparticles (Si NPs) have a great potential for a wide variety of electronic and optoelectronic applications. However, such films are inherently unstable due to their huge surface-to-volume ratios and high surface energies, making them prone to degradation associated to spontaneous oxidation in...
Article
The exploitation of semiconductor nanocrystal (NC) films in novel electronic and optoelectronic applications requires a better understanding of charge transport in these systems. Here, we develop a model of charge...
Article
Full-text available
Mg doping of GaAs nanowires has been established as a viable alternative to Be doping in order to achieve p-type electrical conductivity. Although reports on the optical properties are available, few reports exist about the physical properties of intermediate- to-high Mg doping in GaAs nanowires grown by molecular beam epitaxy (MBE) on GaAs(111)B a...
Data
The supporting information illustrates the fitting model used in the evaluation of the relative intensities of the reflection peaks obtained in grazing incidence X-ray diffraction and presents all PL spectra measured using the excitation power and temperature dependencies for samples A and B.
Article
Self-organizing nanopatterns can enable economically competitive, industrially applicable light-harvesting platforms for thin-film solar cells. In this work, we present transparent solar cell substrates having quasi-periodic uniaxial nanowrinkle patterns with high optical haze values. The self-organized nanowrinkle template is created by controlled...
Article
Abstract The p/i interface plays a major role in the conversion efficiency of nanocrystalline silicon (nc-Si:H) solar cells. Under plasma-enhanced chemical vapor deposition (PECVD) of the intrinsic (i) nc-Si:H layer, ion bombardment can severely affect the underlying p-doped layer and degrade the solar cell performance. The core of the present work...
Article
The influence of Ag nanoparticles (Ag NPs) on the luminescence of electrospun nonwoven mats made of polyvinylpyrrolidone (PVP) has been studied in this work. The PVP fibers incorporating 2.1-4.3 nm size Ag NPs show a significant photoluminescence (PL) band between 580 and 640 nm under 325 nm laser excitation. The down conversion luminescence emissi...
Article
Full-text available
Silver (Ag) and tin (Sn) nanoparticles (NPs) were deposited by thermal evaporation onto heated glass substrates with a good control of size, shape and surface coverage. This process has the advantage of allowing the fabrication of thin-film solar cells with incorporated NPs without vacuum break, since it does not require chemical processes or post-...
Article
Full-text available
The intentional introduction of impurities in semiconductor nanowires is very important in view of device applications. Doping affects the electronic energy levels structure which in the case of III-V nanowires can also be strongly influenced by the simultaneous occurrence of the two polytypes, zinc-blende (ZB) and wurtzite (WZ). In this work, we r...
Article
Full-text available
This work describes the implementation of a low-cost spectrometer produced with common objects and proposed as a pedagogical students’ project. This task aims to introduce the theme of image detection and to stimulate the students to develop skills in the field of optics and photonics. The performance of the developed spectrometer was tested in the...
Article
Full-text available
Metallic nanoparticles (NPs) have received recently considerable interest of photonic and photovoltaic communities. In this work, we report the optoelectronic properties of gold NPs (Au-NPs) obtained by depositing very thin gold layers on glass substrates through thermal evaporation electron-beam assisted process. The effect of mass thickness of th...
Article
Full-text available
Mg-doped GaAs nanowires have been grown by molecular beam epitaxy on a partially Au-coated Si(111) substrate by the vapor-liquid-solid mechanism. Outside the coated areas, a thin film of GaAs was grown epitaxially at the same time. The optical properties in both parts of the sample were investigated by photoluminescence spectroscopy, as a function...
Article
Full-text available
In this work we studied experimentally and theoretically the emission from Ge WL and QDs. The numerical calculations give a prediction for the energy positions of the WL and QDs related emissions in accordance with the PL measurements. The experimental results show an independence of the energy position of the WL related emission of the interaction...

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Projects

Project (1)
Archived project
The LabOPTO project aimed at reinforcing and consolidating the capacities of the I3N/FSCOSD (Aveiro) Associated Research Laboratory in the research and development of micro and nanostructured materials, in which the semiconductors group of I3N/FSCOSD is committed, namely in the areas: i) medical physics and biomedical applications; ii) sustainability and energy efficiency. In the first case it was intended to optimize the optical properties of materials allowing new designs and systems for high energy radiation detectors and the development of new efficient fluorescent materials for bioimaging agents. In the second case, the main target was to develop and characterize highly efficient materials for photovoltaics, solid-state light emitters and NIR photodetectors. During the three years of execution of the LabOPTO project the advanced formation and research activities realized by the LabOPTO team members allowed to pursue and develop cutting-edge and innovative scientific knowledge in the following thematic lines: a) radiation detectors, b) bioimaging agents, c) solid-state lighting, d) solar-energy converters to increase solar cells efficiency, e) NIR photodetectors based on type-II heterostructures and f) thin films for absorber layers in solar cells. The research activities realized lead to the main project outcomes: 4 PhD thesis, 15 MsC thesis, 15 BsC thesis, 20 seminars, 37 oral presentations (invited/ contributed), 99 poster presentations, 70 peer reviewed scientific articles, 3 submitted patents. RECI/FIS-NAN/0183/2012 http://www.fct.pt/apoios/projectos/consulta/vglobal_projecto.phtml.en?idProjecto=126320&idElemConcurso=7534 http://labopto.web.ua.pt/