Nobuyoshi Sakakibara

High Temperature Superconducting Filters for Receiver Front-end of Mobile Telecommunication Base Station

The performance of multi-pole microstrip filters with low insertion loss and sharp-skirt using YBa2Cu3O7-δ high temperature superconducting thin films is presented. The HTS films were deposited on both sides of substrates by a DC sputtering method. The surface resistance of the films was about 0.35mΩ (at 70k and l0GHz). A 9-pole bandpass filter was designed at 2.6GHz center frequency with bandwidth 34MHz. The filter was fabricated using 40mm X 25mm HTS films on a 0.5-mm thick MgO substrate. The insertion loss at 70 K was about 0.ldB with 0.ldB ripple and the minimum return loss was about 20 dB across the passband of the filter. In addition, a 15-pole bandpass filter whose center frequency and bandwidth were 1.53GHz and 60MHz respectively was fabricated using 50-mm diameter HTS film on 0.5-mm thick LaAlO3 substrate. The insertion loss at 70K was less than O.ldB and the rejection level was more than 70dB at the rejection band.

High mobility metal-oxide-semiconductor transistor with high temperature annealed thick polycrystalline-silicon films

We studied the regrowth of grains in polycrystalline‐silicon (poly‐Si) films deposited on a SiO2 layer. The poly‐Si films were grown at 610 °C, by low pressure chemical vapor deposition, up to a thickness of 1.5 μm. The films were then annealed at 1200 °C in flowing N2 for regrowth of the grain. The as‐deposited film has small grains and contains many twin boundaries in the grains. In the 1200 °C annealed sample, the grain size strikingly increases to 2 μm, whereas the density of the twin boundaries decreases. Accordingly, metal‐oxide‐semiconductor thin film transistors are fabricated using poly‐Si films annealed at 1200 °C. The field effect mobility augments to 148 and 96 cm2 V−1 s−1 in the n‐ and p‐channel thin film transistors, respectively.

The Performance of the Microstrip Line Resonator and the Bandpass Filter Using YBa 2 Cu 3 O 7-δ Films with a CeO 2 Cap Layer

We investigated the influence that the surface degradation of the YBa2Cu3O7-δ. (YBCO) film during device fabrication exerts on the performances of microstrip line resonators and bandpass filters. The surface of the YBCO films were covered with a CeO2 cap layer to suppress the surface degradation. The microstrip line resonators with a CeO2 cap layer showed the unloaded Q factor (Qu) of 83,400 at 2.6GHz and 70K, while the Qu of the microstrip line resonators without a CeO2 cap layer were 25% lower. The bandpass filters with capacitive interconnections showed almost same frequency response as the one with ohmic interconnections.

Azimuthal dependence of Auger electron spectra observed with a cylindrical mirror analyzer for Si single crystal and amorphous surfaces

Abstract The azimuthal dependence of Auger electron spectra for Si single crystal and amorphous surfaces, Si(LVV) and Si(KLL), observed with a cylindrical mirror analyzer (CMA) were studied in relation to their low-energy electron diffraction (LEED) patterns. For the Si(111)7 X 7 surface, the peak heights of the Si(LVV) Auger electron spectra were observed to have a variation of 15% (maxima to minima) with an azimuth-angle period of 60°, whereas those for the Si(111) and amorphous Si surfaces, displaying diffuse LEED patterns, showed a spectral deviation within 1.0% standard deviation for the azimuth. It was found that the sharp and diffuse LEED patterns had a close relation with the observed Auger spectra obtained by a conventional CMA having a considerably large detection area of Auger electrons.