Fig. 1: Device structure

Fig. 1: SEM micrograph of the fabricated device. The colors are artificially added. Orange indicates Au electrodes and blue indicates the conductive semiconductor. The beam oscillator shown in the figure vibrates along the surface normal. When a 70-Hz wide unstable oscillation was applied from the lower electrode, a highly purified oscillation with a frequency fluctuation of only 80 mHz was generated and observed from the upper electrode.