ABSTRACT
Self-assembled monolayers were investigated for their suitability as two-dimensional scaffolds for the selective growth of alkanethiol edge structures. Heterostructures with chemical contrast could be grown, whose dimensions were governed by both the initial pattern sizes and the process time. n-Octadecanethiol (ODT) was made to expand from the edges of 16-mercaptohexadecanoic acid (MHDA) monolayer patterns. Likewise, 11-mercaptoundecanol (MUD) was grown on MHDA and on ODT monolayer edges. The results of these experiments are in accordance with the moving boundary model for monolayer spreading. In addition to such surface-bound spreading, a vapor-phase contribution to lateral monolayer growth was identified. MUD was observed to be an excellent ink for creating chemical contrast by means of regioselective deposition from a vapor phase. As a proof of principle, ribbons of 11-mercaptoundecanol with submicrometer widths were grown on pentaerythritol-tetrakis(3-mercaptopropionate) edges, and submicrometer wide gold lines were produced by subsequent wet-chemical etching.
Subject(s)
Alkanes/chemistry , Sulfhydryl Compounds/chemistry , Surface-Active Agents/chemistry , Dimerization , Gases , InkABSTRACT
In this report it is described how a gold surface can be treated with an oxygen plasma to become an effective etch mask, with its etch resistive properties based upon electrostatic repulsion. Such a treated gold layer is only temporarily stable and may therefore be employed as a temporary etch barrier that introduces no contaminating species. Deterioration of the barrier properties can be locally expedited in a scheme that is compatible with microcontact printing. This has been achieved by the microcontact printing of a reductant on a fully oxidized gold substrate.
ABSTRACT
Edge lithographic patterning techniques are based on the utilization of the edges of micrometer-sized template features for the reproduction of submicrometer structures. Edge transfer lithography (ETL) permits local surface modification in a single step by depositing self-assembled monolayers onto a metal substrate selectively along the feature edges of an elastomeric stamp. In this report two stamp designs are described that now allow for the use of alkanethiol inks in ETL and their use as etch resists to reproduce submicrometer structures in gold. Anisotropically modified stamps are shown to combine the potential for very high-resolution patterning with the versatility and simplicity of microcontact printing.
Subject(s)
Alkanes/chemistry , Gold/chemistry , Nanostructures/chemistry , Nanostructures/ultrastructure , Nanotechnology/methods , Printing/methods , Sulfhydryl Compounds/chemistry , Ink , Materials Testing , Particle Size , Surface PropertiesABSTRACT
Poly(dimethylsiloxane) (PDMS) is the most widely used stamp material in microcontact printing. It has excellent properties with respect to versatility, chemical inertness, and mechanical stability. However, it has an inclination to contaminate printed substrates with low molecular weight siloxane fragments. In this study, it is shown, by a combination of lateral force microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, that the extent of the PDMS-induced contamination is dependent on the nature of the ink used. The highest degree of contamination was found for relatively polar inks, whereas apolar alkanethiol inks were found to shield the substrate from contamination. This is interpreted in terms of the contaminating species being polar in nature.
ABSTRACT
Locally oxidized patterns on flat poly(dimethylsiloxane) stamps for microcontact printing were used as a platform for the transfer of a hydrophilic fluorescent ink to a glass substrate. The contrast was found to be limited. These locally oxidized patterns were conversely used as barriers for the transfer of hydrophobic n-octadecanethiol. In this case a good contrast was obtained, but the pattern was found to be susceptible to defects (cracks) in the barrier layer. Local stamp surface oxidation and subsequent modification with 1H,1H,2H,2H-perfluorodecyltrichlorosilane, for use as a barrier in the transfer of n-octadecanethiol, 16-mercaptohexadecanoic acid, and octanethiol, resulted in remarkably good contrast and stable patterns. The improved ink transfer control is ascribed to the reduction of undesired surface spreading and a superior mechanical stability of the stamp pattern. This new approach substantially expands the applicability of microcontact printing and provides a tool for the faithful reproduction of even extremely low filling ratio patterns.
ABSTRACT
Spreading in microcontact printing refers to the process or processes by which the ink molecules end up in the parts of the substrate that are adjacent to the contacted areas but which are not contacted themselves. This has been investigated for different inking concentrations of 16-mercaptohexadecanoic acid (MHDA). Spreading of MHDA takes place with retention of a well-defined demarcation. Feature sizes can be controlled by varying the contact times. Spreading, however, only takes place beyond a certain threshold concentration. For low ink concentrations the edges of stamp features dominate the ink transfer. For these low concentrations the extent of this edge dominance depends strongly on ink concentration rather than on contact time. These observations indicate a dominant role of the stamp surface in the processes of pattern formation and spreading.
