The influence of drying temperature on the close packed structure of silanized monolayers deposited on indium tin oxide
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Valentin Barna Faculty of Physics, University of Bucharest, 077125 Bucharest, Romania
Nicola Scaramuzza,a) Giuseppe Strangi, and Roberto Bartolino INFM-CNR-LICRYL Laboratory and CEMIF.CAL, Department of Physics, University of Calabria, Rende (CS), I-87036 Italy (Received 2 March 2009; accepted 5 June 2009)
Molecular organization of self-assembled n-dimethyl-n-octadecyl-3aminopropyltrimethoxysilychloride (DMOAP) layers on indium tin oxide (ITO) coated glass substrates was thoroughly investigated. The layer thickness for each deposition was determined by variable angle spectroscopic ellipsometry (VASE), while from static contact-angle measurements we deduced valuable information regarding the ordering of the molecular structures at the solid-air interface. In particular, the DMOAP thin film formation was studied for two different drying temperatures (85 C and 120 C). While at Tdrying = 85 C we observed the formation of a molecular monolayer characterized by a close packed structure, at the higher temperature the DMOAP molecules “bend” at the substrate as they stack in relatively disordered clusters. A qualitative interpretation of this phenomenon is given, in good agreement both with the obtained experimental data and experimental investigation reported in the scientific literature. The observations regarding the DMOAP molecular level organization as a function of substrate temperature could bring essential information to the self assembly research community and also explain some important physical phenomena occurring at interfaces.
I. INTRODUCTION
Self-assembled monolayers (SAMs) of organic thin films have manifested increasing interest in many application fields over the last years. These modified surfaces find uses in pharmacological and biological applications, but also in chemistry, materials science, and surface science.1–6 Recently, investigations have also been made in the nanotechnology area; SAMs are successfully used in nanolithography techniques for obtaining nanostructures.7,8 The combination of conventional lithographical and SAM techniques will definitely find its way toward further interesting applications in the nanomaterials and nanostructures arena.9 The self-assembly (SA) processes have lately been analyzed in great detail and a lot of information about the physical and chemical properties and the experimental parameters can be found in the research literature.1,2,10 Amphiphilic molecules can organize themselves into higher order structures of molecular monolayers at varia)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0337
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http://journals.cambridge.org
J. Mater. Res., Vol. 24, No. 9, Sep 2009 Downloaded: 13 Mar 2015
ous types (liquid-liquid, air-liquid, and solid-air) of boundary interfaces. Several other techniques are also used for obtaining molecular monolayers at different interfaces. Langmuir-Blodgett (L-B) films are amphiphilic molecular monolayers organized at one interface (typically air-liquid) that are transferred to
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