Local heat generated by a focused He⁺ ion beam

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Focused helium ion (He+) microscopy enables high-resolution imaging and modification of materials.
• Understanding localized heating effects is crucial for precise nanofabrication.
• Gold nanostructures exhibit size-dependent melting points, useful for thermometry.

Purpose of the Study:

• To quantify the localized surface temperature generated by a focused He+ beam.
• To investigate the potential of this heating for direct nanomaterial modification.
• To evaluate the feasibility of using gold nanodisks as in-situ thermometers.

Main Methods:

• Utilized a focused He+ beam with a diameter < 1 nm and a dose > 1 × 10^20 ions cm^-2.
• Fabricated gold nanodisks (20 nm diameter, 10 nm thickness) on mica and sapphire substrates.
• Determined temperature by observing the melting and vaporization of gold nanodisks based on their size-dependent melting points.

Main Results:

• Achieved localized surface temperatures up to 1000°C.
• Observed surface decomposition and chemical reactions due to localized heating.
• Demonstrated the utility of gold nanodisks for in-situ temperature measurement in the nanometer scale.

Conclusions:

• Focused He+ beams can induce significant localized heating, suitable for direct nanomaterial nano-sculpting.
• This resistless approach is advantageous on highly thermally conductive supports like sapphire.
• The method is detrimental for precise He+ nanolithography resist processes but promising for direct material modification.