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

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Fabricating nanoscale patterns on silicon surfaces often requires complex wet chemical etching.
• Self-assembled monolayers (SAMs) on silicon offer potential as resist layers for lithography.
• Atomic force microscopy (AFM) lithography provides high-resolution patterning capabilities.

Purpose of the Study:

• To develop an in-situ method for fabricating negative nanopatterns on silicon surfaces.
• To investigate the role of surface treatments and AFM parameters in nanopattern formation.
• To propose a mechanism for silicon pore formation during AFM lithography.

Main Methods:

• Utilized tetradecylated Si(111) surfaces functionalized with alkyl self-assembled monolayers (SAMs).
• Employed bias-dependent atomic force microscopy (AFM) lithography for in-situ pattern generation.
• Applied dilute hydrofluoric acid (HF)-ethanol treatment to the SAM-covered silicon substrate prior to lithography.

Main Results:

• Successfully fabricated negative nanopatterns, specifically silicon pores, without wet chemical etching.
• Demonstrated the ability to create both negative (Si pores) and positive (oxide dots) patterns by varying AFM bias and pulse duration.
• Identified the HF-ethanol treatment as crucial for the in-situ formation of negative nanopatterns.

Conclusions:

• Bias-dependent AFM lithography on SAM-functionalized silicon offers a direct route to in-situ nanopattern fabrication.
• The formation of silicon pores is attributed to the reaction between fluoride ions and the silicon substrate, induced by the AFM tip's electric field.
• This approach provides a versatile and efficient method for creating diverse nanopatterns on silicon surfaces.