Strain versus Tunable Terahertz Nanogap Width: A Simple Formula and a Trench below

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Flexible metallic structures with tunable gaps are essential for advanced electronic applications.
• The precise relationship between applied strain, periodicity, and gap width in zerogap structures remains poorly understood.
• The underlying mechanism for tunability in these flexible systems requires further investigation.

Purpose of the Study:

• To investigate the relationship between strain and gap width in a flexible zerogap metallic structure.
• To elucidate the mechanism responsible for the tunable gap width.
• To correlate the physical structure with terahertz and visible transmission properties.

Main Methods:

• Fabrication of a flexible zerogap metallic structure on a polymer substrate.
• Application of compressive strains to tune the gap width.
• Atomic force microscopy (AFM) for high-resolution surface imaging.
• Terahertz and visible spectroscopy to analyze transmission properties.

Main Results:

• Periodic 200 nm-deep nano-trenches were observed on the polymer substrate beneath the zerogap structure.
• Strain singularities between metallic deposition layers were identified as the cause of nano-trench formation.
• The gap size was found to be linearly dependent on the inverse of the radius of curvature of the polyethylene terephthalate (PET) substrate.

Conclusions:

• The study reveals that strain singularities drive the formation of nano-trenches, enabling tunable gap widths in flexible zerogap metallic structures.
• The findings provide a clear mechanism for the continuous tunability of zerogap structures from nearly zero to 100 nm.
• The linear relationship between substrate bending and gap size offers a predictable method for controlling device performance.