The reactivity of scribed silicon with epoxides, aldehydes, and acid chlorides; analysis of scribed silicon by TOF-SIMS; and, chemomechanical surface patterning with a tungsten carbide ball.

摘要

Here I describe a new and simple method for preparing alkyl monolayers on silicon, which consists of chemomechanically scribing oxide-coated or hydrogen-terminated silicon while it is wet with 1-alkenes, 1-alkynes, 1-haloalkanes, alcohols, epoxides, aldehydes, and acid chlorides under ambient conditions. X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), wetting data, and stability tests suggest covalent bonding of unsaturated species to exposed silicon surfaces. This patterning method can be extended to create individual surfaces that have different monolayer coatings in distinct and precisely controlled regions. Like microcontact printing, this technique allows multiple, patterned, surface features to be prepared with ease. A series of mixed monolayers can also be prepared from mixed chemicals, and more importantly, I demonstrate that amine-reactive mixed monolayers can be formed on scribed silicon from mixtures containing an alpha,o-diepoxide, or an alpha,o-diacid chloride.; Although this method is facile, the features produced in the earliest studies using 2--3 N of force on a diamond tip are irregular, broad (∼100 mum), and deep (∼5 mum). Here I show that substantially sharper and shallower features are produced by (a) wetting hydrogen-terminated silicon with a reactive compound and (b) scribing it with a tungsten carbide ball with a low force (∼0.08 N). It is remarkable that the depth of these features is only 10--20 A, their edge widths are sharp and the line widths are narrower (10--20 mum). The resulting features are invisible to the naked eye but are observable by atomic force microscopy (AFM), scanning electron microscopy (SEM), and ToF-SIMS. Miniature hydrophobic corrals made with this technique can be loaded with solutes, for example, colloidal carbon, semiconductor nanocrystals, and DNA, from aqueous solutions with a simple dip. This new patterning method has also been used for assisting Cu selective deposition on silicon surfaces, and for growing uniform, covalently attached polymers onto silicon surfaces.; Improved methods to enhance ion yield and cationization for SIMS have been sought for since the inception of the SIMS technique more than 30 years ago. Here we demonstrate for the first time that a polyelectrolyte multilayer can significantly enhance the ion yields of complex organic molecules (macrocycles). The enhancement can be as large as 10 times compared to the neat macrocycles. Significant enhancements in various large fragment ions from the macrocycles were also found.