Si-Cr Nano-Alloys Fabricated by Direct Femtosecond Laser Writing

Area of Science:

• Materials Science
• Nanotechnology
• Laser Physics

Background:

• Developing precise methods for creating nanoscale features is crucial for advanced material processing.
• Chromium (Cr) etch masks are widely used in microfabrication, but precise nanoscale patterning remains challenging.

Purpose of the Study:

• To investigate the use of ultra-short laser pulses for fabricating nano-holes in thin Cr films.
• To explore the formation of nanostructures (nano-disks and nano-rings) by controlling laser pulse energy.
• To demonstrate large-area, vacuum-free patterning of nanolayers with sub-diffraction resolution.

Main Methods:

• Utilizing ultra-short (230 fs) laser pulses at 515 nm wavelength, tightly focused to 700 nm spots.
• Precisely controlling laser pulse energy to ablate Cr etch masks and induce nano-alloying with silicon (Si).
• Characterizing the resulting nanostructures and their resistance to Cr and Si etching processes.

Main Results:

• Fabrication of approximately 400 nm nano-holes in tens-of-nm thick Cr masks.
• Determined an ablation threshold of 2.3 nJ/pulse for the Cr mask, double that of plain silicon.
• Observed the formation of nano-disks below the ablation threshold and nano-rings above it.
• Demonstrated controlled nano-alloying of Si and Cr over large areas with sub-1 nJ pulse energy control.
• Resulting nanostructures were resistant to both Cr and Si etchants.

Conclusions:

• Ultra-short laser pulses enable precise, sub-diffraction-limited patterning of Cr etch masks.
• Controlled laser-induced nano-alloying facilitates vacuum-free large-area patterning of nanolayers.
• The fabricated nano-hole masks are suitable for creating random patterns of nano-needles for silicon dry etching.