Nanogram calorimetry using microscale suspended SiNx platforms fabricated via focused ion beam patterning

Area of Science:

• Materials Science
• Nanotechnology
• Thermal Physics

Background:

• Accurate thermal characterization of nanoscale heterostructures necessitates microscale platforms with high thermal isolation and sensitive thermometry.
• Amorphous silicon nitride (SiNx) membranes are commonly employed due to their low thermal conductivity and fabrication compatibility, though their thermal conductance is often in the microwatts per kelvin range.

Purpose of the Study:

• To engineer and demonstrate microscale platforms with substantially reduced thermal coupling for enhanced nanoscale thermal measurements.
• To achieve thermal conductance significantly lower than conventional SiNx membranes for improved sensitivity.

Main Methods:

• Utilized focused ion beam (FIB) milling to precisely remove material from commercial amorphous SiNx membranes.
• Fabricated a 100 μm × 100 μm suspended platform supported by narrow legs, drastically reducing thermal pathways.
• Employed the platform to measure the heat capacity of a 6.2 ng gold (Au) sample.

Main Results:

• Achieved a thermal conductance of 120 nW/K for the fabricated SiNx platforms, a significant reduction from typical values.
• The measured heat capacity of the gold sample closely matched established values for bulk gold.
• Demonstrated the platform's efficacy for sensitive thermometry and thermal property measurements at the nanoscale.

Conclusions:

• The FIB-milled SiNx platforms offer superior thermal isolation for precise nanoscale thermal measurements.
• These platforms are a valuable tool for advancing the study of thermal properties in nanomaterials and heterostructures.
• The methodology provides a pathway for fabricating highly sensitive microscale thermal measurement devices.