Observation of Interface Piezoelectricity in Silicon*

The piezoelectric effect is the ability of certain materials to generate electric potential when subjected to mechanical deformation, and conversely, to deform when an electric field is applied to them. While piezoelectricity is present only in non-centrosymmetric crystals, recent theoretical work showed that centrosymmetric crystals such as sapphire [1] and silicon can exhibit surface or interface piezoelectricity from inversion-symmetry-breaking at interfaces. Even though this effect can cause a significant dissipation channel for superconducting qubits, it has not yet been observed in experiments. 

In this talk, I will report on our recent observation of the interface piezoelectric effect in crystalline silicon. I will introduce our experimental setup based on gigahertz-frequency surface acoustic wave (SAW) transducers. We use an interdigital transducer (IDT) on bulk piezoelectric material to launch SAWs and use another IDT sitting directly on silicon to sense the piezoelectric signal. I will discuss the time-domain analysis of the detected signal and the possible underlying physical mechanisms. I will end by discussing how interface piezoelectricity may impact superconducting qubit performance, and present methods of mitigating this loss mechanism via phononic engineering.

[1] A. B. Georgescu and S. Ismail-Beigi, Phys. Rev. Applied 11, 064065 (2019)