In-situ negatively nanopatterning alkylated silicon (111) surface by conductive atomic force microscope.

Negative nanopatterns have been successfully in-situ fabricated on tetradecylated Si(111) surface via bias-dependent atomic force microscopy (AFM) lithography without wet chemical etching procedures. Alkyl self-assembled monolayers (SAMs) made of 1-tetradecene coupled to hydride-terminated Si(111) surface through robust silicon-carbon covalent bonds was employed as a resist layer. The SAM covered silicon substrate was then treated with dilute hydrofluoride, and subsequent used in AFM lithography. By varying the applied bias and pulse duration, both negative and positive patterns can be fabricated via this approach, such as Si pores and oxide dots. The results indicated that the HF-ethanol treatment of SAMs plays an important role in forming negative nanopatterns in situ. In particular, the Si pore structure formation was related to the reaction between F-buried inside the SAM and silicon substrate under the effect of tip electric field. A possible mechanism of Si pore formation based on the reaction of F- ions with silicon induced by the tip bias was proposed.