Mesoscopic Ni particles and nanowires by pulsed electrodeposition into porous Si
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RESEARCH PAPER
Mesoscopic Ni particles and nanowires by pulsed electrodeposition into porous Si E. Michelakaki • K. Valalaki • A. G. Nassiopoulou
Received: 30 November 2012 / Accepted: 9 February 2013 / Published online: 10 March 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract We report in this article on the formation of mesoscopic Ni particles and filling of continuous Ni nanowires into porous Si layers of thickness in the range of 0.5–4 lm with anisotropic vertical pores of average diameter in the range of 30–45 nm using pulsed electrodeposition from a Ni salt solution. The effect of pulse duration, number of pulses, and total process time on pore filling was investigated for porous Si with different porosities and porous Si layer thicknesses in the above thickness range. Scanning and transmission electron microscopy were used to characterize the samples. It was found that pore filling starts with Ni nucleation and nanoparticle formation at different points of the pore walls along the whole pore length and continues with nanoparticle coalescence to form continuous Ni nanowires that completely fill the pores. The mechanism involved in pore filling is particle nucleation and diffusion-controlled growth of Ni nanoparticles that coalesce to nanowires. From the beginning of the process, a metal film starts to form on the porous Si surface, and its thickness increases with increasing the
Special Issue Editors: Juan Manuel Rojo, Vasileios Koutsos This article is part of the topical collection on Nanostructured Materials 2012 E. Michelakaki K. Valalaki A. G. Nassiopoulou (&) NCSR ‘‘Demokritos’’/IMEL, Terma Patriarchou Grigoriou, Aghia Paraskevi, 15310 Athens, Greece e-mail: [email protected]
process time. However, the presence of this film does not impede further pore filling and nanowire formation into the pores. This supports further the diffusioncontrolled growth mechanism. Finally, it was demonstrated that full pore filling and continuous Ni nanowire formation were also achieved under direct current electrodeposition, and the results are quite similar to those obtained with pulsed electrodeposition when the same total deposition time is used in both cases. Keywords Ni nanoparticles Ni nanowires Porous Si Electrodeposition
Introduction With the accelerated development of nanotechnology, nanoparticles and nanowires constitute a fast growing research field involving Physics, Chemistry, Biology, Engineering Science and Medical Science with a large variety of applications. Electrodeposition is one of the most important techniques for depositing metals at the nano- and micrometer scale and has gained an increasing interest in the recent years for use in many fields. In the field of electronics, the interest in electrodeposition has been accelerated since its application in Cu metallization of integrated circuits (ICs) (Andricacos et al. 1998) using the damascene process, but other important applications are emerging, including magnetic nanostructures for use in magnetic
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