The effect of solvent and electric field on the size distribution of iron oxide microdots: Exploitation of self-assembly
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ateusz Schabikowski Laboratory for High Performance Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland; and Faculty of Materials Science and Ceramics, AGH University of Science and Technology, PL - 30-059 Krakow, Poland
Jakob Heier Laboratory for Functional Polymers, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
Artur Braun Laboratory for High Performance Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
Dariusz Kata Faculty of Materials Science and Ceramics, AGH University of Science and Technology, PL-30-059 Krakow, Poland
Thomas Graule Laboratory for High Performance Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland; and Technische Universität Bergakademie Freiberg, D-09599 Freiberg, Germany (Received 13 May 2010; accepted 14 September 2010)
An increasing number of technologies benefit from or require patterned surfaces on a micro- and nanoscale. Methods developed to structure polymer films can be adapted to fabricate low-cost patterned ceramics using nonlithographic techniques, for example, dewetting and phase separation in thin films. In this paper we describe a simple patterning process that does not require a template and is able to produce Fe2O3 microdots with a spatial periodicity. Our method involves the dewetting of a silicon substrate by a thin metal oxide precursor film, in which the liquid film breaks up because of fluctuations in the film thickness induced by solvent evaporation or an external applied electric field. The patterning is followed by a thermal treatment at 550 °C to produce crystalline Fe2O3 microdots with a diameter range of 200 nm to 3 lm. I. INTRODUCTION
Pattern formation due to dewetting thin films can be of vital importance in nanotechnology, with the possibility of designing patterned surfaces for specific applications, for example, photoelectrodes, optical devices, and sensors. Early studies of the dewetting of thin polymer films on silicon substrates were reported by Reiter1 using polystyrene. This and subsequent studies of thin nonvolatile liquid films on nonwetting substrates2 have identified dewetting as a three-stage process. In the first stage, the film breaks up into randomly distributed holes. This is followed by the growth of the holes, resulting in the a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2010.4 254
J. Mater. Res., Vol. 26, No. 2, Jan 28, 2011
http://journals.cambridge.org
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formation of a polygonal network of straight liquid rims. In the final stage, the rims become unstable and break up by Rayleigh instability to form an array of dots. These initial studies showed that the average distance d between the holes scales with the second power of the thickness l of the film: d l2. In theoretical studies, two possible rupture mechanisms have been considered: heterogeneous
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