Nesma Nafie

Centre des Recherches et des Technologies de l'Energie, Hamman-Lif, Tūnis, Tunisia

Are you Nesma Nafie?

Claim your profile

Publications (6)11.03 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Morphological, optical and electrical properties of SiNWs are studied under different preparation conditions. Despite an ultra-low reflectivity revealing a high light-trapping effect, we obtained a degradation of the resistivity and the minority carrier lifetime in SiNWs which are ascribed to a high electron-trapping. For solar cells application, we determine a trade-off between optical and electrical properties of SiNWs. However, even with this optimization, we obtained a degradation of the electrical parameters of the solar cell when SiNWs are used as compared to the cell without SiNWs. From the obtained results in this work, we put in evidence for the first time that despite the very low reflectivity that a SiNWs film has, its use in PV is faced to four major challenges; (1): an unbalancing between the length of SiNWs and the electron diffusion length, (2): a thick SiO2 layer covering silicon wires formed during the solar cell processing (observed using dark field transmission electron microscopy), (3) a high density of dangling bonds of porous-SiNWs when the SiO2 film is etched, and, (4) a poor metal/SiNWs front contact.
    Solar Energy 11/2014; 110. DOI:10.1016/j.solener.2014.10.007 · 3.47 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Silver and gold assisted etching of silicon in an HF aqueous solution is studied in this work. In the literature, we found that such etching leads to the formation of a variety of structures; i.e. silicon nanowires (SiNWs) or porous silicon (PS). It is also reported that the role of metals during the etching can be a catalyzing role (Peng et al., Adv. Mater. 23, 198 (2011) [1]) or a protective role (Qiun and Chu, Mater. Sci. Eng. R 61, 59 (2008) [2]). In addition, we found that for a sole experimental protocol, silver is described to have both roles. In this study, this apparent sole experimental protocol is divided into two different experimental ones; the one step process (OSP) and the two steps process (TSP). For each process, we propose an etching mechanism. We give experimental evidences arguing that the protective effect occurs during the OSP and the catalyzing effect occurs during the TSP. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 02/2014; 11(2). DOI:10.1002/pssc.201300120
  • [Show abstract] [Hide abstract]
    ABSTRACT: Silicon nanowires (SiNWs) become interesting nanostructures for several applications such as electronic, photovoltaic, and maybe in a short future as nanopower source for nanorobotics. There are several experimental methods to form SiNWs. In this study, we use the etching assisted silver method in a HF solution. We investigate the effect of the doping concentration (P and P+ silicon) on the morphological, optical and electronic properties of silicon nanowires prepared at different etching times. We found that the morphological, optical and electronic properties of the formed films depend on the doping level of the used silicon substrate. The total reflectivity of some films reaches 1%. However, a decrease of the measured effective lifetime as a function of the etching time is obtained. Using the light-beam-induced-current (LBIC) profiles measured on a MIS structure fabricated on P and P+-SiNWs, we found that the effective diffusion length is in the range of 100μm for P+-SiNWs, however it is only in the range of 60μm for P-SiNWs. This was attributed to the reflectivity and homogeneity of the formed films.
    Physica E Low-dimensional Systems and Nanostructures 02/2014; 56:427-430. DOI:10.1016/j.physe.2012.10.007 · 2.00 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The discovery at the beginning of 1990 of carbon nano-tubes awaked the interest for one-dimensional (1D) nanostructures. Currently, silicon nanowires (SiNWs) formed by electroless chemical etching in aqueous Ag-NO3/HF/H2O2 solution, arouse great interest due to their physical properties and potential applications. The understanding of physical-chemical phenomena that occur during the formation of SiNWs, the effect of etching parameters on their morphology, the formation mechanism and formation kinetic raise many questions. In this paper, we investigate the effect of etching parameters; namely AgNO3 concentration, HF concentration, etching time and the volume of H2O2 on the shape of obtained nanostructures. The formation kinetic was investigated by studying the effect of the etching time on the morphology of obtained nanostructures. SiNWs studied in this work were formed on a P type and (100) oriented monocrystalline silicon substrate. Characterization of formed SiNWs was performed using a scanning electron microscope (SEM). (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 02/2014; 11(2). DOI:10.1002/pssc.201300172
  • Source
    Manel Abouda-Lachiheb · Nesma Nafie · Mongi Bouaicha ·
    [Show abstract] [Hide abstract]
    ABSTRACT: It was reported that during silicon etching, silver was subjected to have a controversial role. Some researchers debate that silver protects silicon, and, at the same time, other ones confirm that silver catalyzes silicon underneath. In this paper, we give experimental results arguing the dual role that silver has during the formation of silicon nanostructures. We give a proof that the role of silver depends on the experimental details and the intrinsic properties of silver during its deposition on the silicon wafer. Through our investigations, we tracked the silver particles that indicated which mechanism is involved. Characterizations of the prepared samples were made using a scanning electron microscope.
    Nanoscale Research Letters 08/2012; 7(1):455. DOI:10.1186/1556-276X-7-455 · 2.78 Impact Factor
  • Source
    Nesma Nafie · Manel Abouda Lachiheb · Mongi Bouaicha ·
    [Show abstract] [Hide abstract]
    ABSTRACT: Owing to their interesting electronic, mechanical, optical, and transport properties, silicon nanowires (SiNWs) have attracted much attention, giving opportunities to several potential applications in nanoscale electronic, optoelectronic devices, and silicon solar cells. For photovoltaic application, a superficial film of SiNWs could be used as an efficient antireflection coating. In this work we investigate the morphological, optical, and electronic properties of SiNWs fabricated at different etching times. Characterizations of the formed SiNWs films were performed using a scanning electron microscope, ultraviolet-visible-near-infrared spectroscopy, and light-beam-induced-current technique. The latter technique was used to determine the effective diffusion length in SiNWs films. From these investigations, we deduce that the homogeneity of the SiNWs film plays a key role on the electronic properties.
    Nanoscale Research Letters 07/2012; 7(1):393. DOI:10.1186/1556-276X-7-393 · 2.78 Impact Factor