Catalytic Silane Nanopatterning using Scandium Triflate Functionalised PPL Arrays

Access to files

•   FULL-TEXT.PDF (pdf)

Abstract

Nanolithography describes procedures for the production of nanoscale features (<100nm) on surfaces by removal (top-down nanofabrication) or deposition (bottom-up nanofabrication) of material. Such procedures have broad applications in nanodevice production. Current methods for bottom-up nanolithography of covalently bound compounds on silicon substrates generally require pre-functionalisation of the surface, for example by deposition of organic species or coating with a suitable metal. While these approaches permit effective lithographic generation of a wide range of surface functionalities, pre-functionalisation requires specialist equipment or use of water sensitive chemicals that may be prone to self-polymerise, necessitating careful control of conditions to ensure formation of regular surface structures. A simple and effective procedure for direct lithography of organic species on to oxidised silicon to generate covalently attached chemical features would simplify surface nanofabrication by reducing the need for such technical pre-treatments. This work examines an approach to that end. Scandium triflate is a water-stable Lewis acid that demonstrates high catalytic activity in a variety of traditional Lewis acid catalysed reactions. A procedure for the covalent functionalisation of oxidised silicon substrates with methallylsilanes using catalytic scandium triflate has been demonstrated. The reagents used in these procedures are typically stable in the presence of water and in the absence of a Lewis acid catalyst, enhancing control of their reactivity. This dissertation explores means of adapting this chemistry to nanolithographic protocols to permit direct lithography of methallylsilane-derived features on to oxidised silicon substrates. Two approaches were adopted to this end. First, molecular scandium triflate was used in procedures for dip-pen polymer pen lithography of dodecyltris(2-methallyl)silane on oxidised silicon. Features of 2.5±0.28 μm were successfully generated with good reliability and repeatability. Smaller features of 439±70nm were produced with reduced but moderate reliability. Second, attempts were made to tether a scandium triflate catalyst to a PDMS polymer pen lithography array to permit its repeated use in nanolithography. Functionalisation protocols were developed and tested on silicon substrates. Contact angle goniometry and x-ray photoelectron spectroscopy evidenced functional changes at the substrate surfaces including the presence of scandium in certain cases. Further attempts to characterise the surface yielded poor results. One of the functionalisation protocols was performed on PPL arrays. These were used in attempts to perform catalytic nanolithography of dodecyltris(2-methallyl)silane on to oxidised silicon substrates. Lithography features detectable by atomic force microscopy were not successfully generated. Further work in this area is required.

Keyword(s)

AFM; Nanofabrication; Nanolithography; PPL; Polymer Pen Lithography; Scandium Triflate

Bibliographic metadata

Institutional metadata

Record metadata