High-resolution constant-height imaging with apertured silicon cantilever probes

Area of Science:

• Nanotechnology
• Optical Microscopy
• Surface Science

Background:

• Conventional atomic force microscopy (AFM) cantilevers lack optical functionality.
• Scanning near-field optical microscopy (SNOM) requires specialized probes for high-resolution optical imaging.
• Integrating AFM and SNOM can provide complementary surface information.

Purpose of the Study:

• To develop and characterize high-resolution aperture probes for simultaneous AFM and near-infrared SNOM.
• To investigate the resolution limits and influencing factors of these novel probes.
• To enable artifact-free optical imaging at low scan heights.

Main Methods:

• Modification of silicon AFM cantilevers by coating with an opaque aluminum layer.
• Fabrication of sub-50 nm apertures using focused ion beam (FIB) milling.
• Operation in constant-height mode to eliminate distance control artifacts.
• Analysis of distance dependence and cantilever bending effects on optical images.

Main Results:

• Successful fabrication of aperture probes with apertures less than 50 nm.
• Achieved a spatial resolution of approximately 50 nm (lambda/20) at the used wavelength.
• Demonstrated the capability for simultaneous AFM and near-infrared SNOM.
• Identified the influence of cantilever bending on optical images at low scan heights.

Conclusions:

• The developed aperture probes enable high-resolution simultaneous AFM and SNOM.
• Focused ion beam milling is effective for creating sub-50 nm apertures on AFM cantilevers.
• Understanding probe-surface interactions is crucial for accurate low-height scanning.