High-Q, gallium nitride nanowire-ALD composite mechanical resonators

We are investigating high quality-factor, Q, gallium nitride (GaN) nanowire (NW) - atomic layer deposition (ALD) composite nano-electromechanical resonators. GaN-NWs of typical 100 nm radius and a few microns length are single crystal structures grown by molecular beam epitaxy. These NWs are singly-clamped cantilevers, resonate near 1 MHz, and have typical Q in the range 10
⁴
-10
⁵
under high vacuum. We are exploring the potential for surface functionalization and resonance frequency tuning of these high-Q resonators through ALD coatings. We report that thin coatings (<10 nm) of ALD Al
₂
O
₃
lead to a broadening of the GaN-NW fundamental mode resonance peak and a consistent increase in resonance frequency of ~15 kHz per 5 nm ALD.