Hierarchical tensile structures with ultralow mechanical dissipation.

Area of Science:

• Nanotechnology
• Mechanical Engineering
• Materials Science

Background:

• Structural hierarchy is prevalent in nature and engineered systems, improving performance.
• Mechanical resonators often suffer from energy dissipation, limiting their sensitivity.
• Hierarchical designs can offer novel ways to reduce dissipation in mechanical systems.

Purpose of the Study:

• To apply hierarchical design principles to silicon nitride nanomechanical resonators.
• To investigate the dissipation reduction and performance enhancement of these hierarchical resonators.
• To explore their potential in advanced sensing and quantum technologies.

Main Methods:

• Fabrication of binary tree-shaped silicon nitride nanomechanical resonators.
• Characterization of resonator quality factors at room temperature and cryogenic conditions.
• Measurement of thermal-noise-limited force sensitivity.

Main Results:

• Achieved room temperature quality factors up to 7.8 × 10⁸ at 107 kHz.
• Observed quality factors of 1.1 × 10⁹ at 6 K.
• Demonstrated force sensitivities of 740 zN/Hz^1/2 (room temperature) and 90 zN/Hz^1/2 (6 K).
• Developed hierarchically structured membranes for interferometric measurements.

Conclusions:

• Hierarchical design enables ultralow dissipation in nanomechanical resonators via soft clamping.
• These resonators surpass current cantilevers in force microscopy applications.
• Hierarchical resonators and membranes offer new possibilities for force sensing, signal transduction, and quantum optomechanics.