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To investigate a higher frequency microelectromechanical systems (MEMS) resonator, mechanical behaviors and electrical characteristics on a single-crystal-silicon MEMS resonator, utilizing a narrow gap process, have been evaluated. The size reduction for the resonators leads to a decrease in output signal. To overcome this problem, an increase in electromechanical coupling coefficient is required. To investigate the effect of the reduction of the gap between a beam and a driving electrode, two types of 100 kHz MEMS resonator with different gaps have been fabricated and compared. It has been observed that the resonator with a narrow gap (1 µm) has a larger displacement amplitude, as well as a larger phase transition, than that with a 4 µm gap, which suggests that the gap reduction is effective. Then, a 10 MHz MEMS resonator has been fabricated by using the narrow gap process with a focused-ion beam (FIB). The resonant vibration for the fabricated device has been observed at 11.262 MHz. To further improve the resonators, it is suggested that the substrate vibration near the beam resonant frequency should be suppressed and that a smooth surface of the gap should be fabricated.

No abstract

A dot‐in‐well structure for quantum dot (QD) growth on InP (001) vicinal substrates was introduced to increase the emission wavelength. The emission wavelength of the QDs changed from 1600 nm in conventional structures to 1850 nm in the proposed dot‐in‐well structure, when measured at room temperature. The emission intensity of this dot‐in‐well structure was the same as that of the conventional structure, implying that the dot‐in‐well structure did not degrade crystal quality.

We measured two-dimensional spectra for photon pairs generated from biexciton in CuCl, changing the crystal temperature. Spectral diffusion by the degradation of the biexciton state appeared in a specific direction in the two-dimensional spectrum.