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On the formation of the porous structure in nanostructured a-Si coatings deposited by dc magnetron sputtering at oblique angles

By Vanda Cristina Fortio Godinho, P. Moskovkin, Rafael Álvarez, Jaime Caballero Hernández, R. Schierholz, B. Bera, J. Demarche, Alberto Palmero Acebedo, Asunción Fernández Camacho and S. Lucas

Abstract

The formation of the porous structure in dc magnetron sputtered amorphous silicon thin films at low temperatures is studied when using helium and/or argon as the processing gas. In each case, a-Si thin films were simultaneously grown at two different locations in the reactor which led to the assembly of different porous structures. The set of four fabricated samples has been analyzed at the microstructural level to elucidate the characteristics of the porous structure under the different deposition conditions. With the help of a growth model, we conclude that the chemical nature of the sputter gas not only affects the sputtering mechanism of Si atoms from the target and their subsequent transport in the gaseous/plasma phase towards the film, but also the pore formation mechanism and dynamics. When Ar is used, pores emerge as a direct result of the shadowing processes of Si atoms, in agreement with Thornton's structure zone model. The introduction of He produces, in addition to the shadowing effects, a new process where a degree of mobility results in the coarsening of small pores. Our results also highlight the influence of the composition of sputtering gas and tilt angles (for oblique angle deposition) on the formation of open and/or occluded porosityEuropean Union CT-REGPOT-2011-1-285895Consejo Superior de Investigaciones Científicas PIE 201060E102, PIE 201460E018Ministerio de Economía y Competitividad CSD2008–00023, CTQ2012-32519, MAT2013-40852-RJunta de Andalucía TEP217 PE2012, TEP862, PE2010-FQM-690

Topics: Porous silicon, Oblique angle deposition, Growth model, Monte Carlo simulation, Magnetron sputtering, Porosity formation, Nanostructure
Publisher: 'IOP Publishing'
Year: 2014
DOI identifier: 10.1088/0957-4484/25/35/355705
OAI identifier: oai:idus.us.es:11441/81125

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