Fig. 1: Observation of interface piezoelectricity via surface acoustic waves.
From: Observation of interface piezoelectricity in superconducting devices on silicon
a Schematic of the 1 × 2 surface reconstruction of silicon (100) surface. Blue spheres: bulk silicon atoms. Red spheres: surface silicon atoms with unpaired bonds (gray). b Schematic of the energy band diagram at the aluminum-silicon interface and the formation of interface dipoles. The green region indicates the interface electronic states induced by aluminum. EC and EV are the energy of the silicon conduction and valence band edges, EF is the Fermi energy, and ECNP is the charge neutrality point of the silicon interface states. c Interface piezoelectricity induced phonon loss in superconducting qubits. d Experiment setup. Aluminum IDTs fabricated on silicon transmit and receive surface acoustic waves. e Microwave transmission coefficient ∣S21∣ as a function of driving frequency measured for devices with different separation distance d on Sample A (Supplementary Fig. 1a). f Time-domain ∣S21∣ as a function of delay time t. The black arrows indicate the onset time of surface acoustic wave transmission (ts). Inset: Δt = ts − tc as a function of d. Here, ts (tc) is the onset of transmission mediated by the surface acoustic waves (capacitive crosstalk). Dashed line: Linear fit d = v ⋅ Δt gives the silicon surface wave velocity v = 5063 m/s. g Time-gated ∣S21∣ as a function frequency for devices with different d. Inset: Time-gated ∣S21∣ at the electromechanical resonance as a function of d. Dashed line: fit. All measurements are conducted at room temperature.
