Fumihiko Toda

Satoru Kishida; Heizo Tokutaka; Fumihiko Toda; Hiroshi Fujimoto; Wataru Futo; Katsumi Nishimori; Naganori Ishihara

The XPS (X-ray photoelectron spectroscopy) measurements of the 80 K-phase Bi-Sr-Ca-Cu-O single crystals were carried out on surfaces obtained by cleaving in vacuum, by cleaving in air and heating in vacuum, and by Ar+-sputter etching of the air-cleaved-and-heated surface. The chemical bond natures of all the constituent elements from the air-cleaved-and-heated surface are approximately equal to those from the vacuum-cleaved surface. Sr and Ca from the sputtered surface are more oxidized than those from the vacuum-cleaved surface.

Fumihiko Toda; Hitoshi Abe

A superconductor-based three-terminal device of In/(Ba, Rb)BiO3/SrTiO3(Nb) structure was produced. The (Ba, Rb)BiO3/SrTiO3(Nb) interface is a Schottky junction with a barrier height of 1.8 eV, while the (Ba, Rb)BiO3/In interface is a junction with rectifying characteristics. The static properties of the three-terminal device as a transistor were determined in common-base and common-emitter configurations. With a base thickness of up to 50 nm, α=0.94 and β=10 were obtained, confirming that this device operated as a transistor.

Hiroyuki Naoe; Yuzuru Mitani; Toshiyuki Kitagawa; Satoru Kishida; Fumihiko Toda; Heizo Tokutaka

We prepared the Ba1-xRbxBiOy (BRBO) thin films on a MgO(100) substrate by rf magnetron sputtering method using a mixture gas of He and O2, and an off-axis geometry, where the substrate was located perpendicular to targets. From the results, we found that the BRBO films prepared using the targets of Ba:Rb:Bi=1:z:1 (z=0.5∼1.0) contained Ba, Rb, Bi and O, and that the films were dominantly (110)-oriented. In addition, the results of electron probe microanalysis indicates that the compositions of the BRBO films were dependent on Rb contents in the targets.

Hiroyuki Naoe; Satoru Kishida; Fumihiko Toda; Yuzuru Mitani; Heizo Tokutaka

We prepared the BaRbBiO(BRBO) thin films by rf magnetron sputtering using He+O2 gas(He=80%) at the substrate temperatures(Tsub) from room temperature(RT) to 450°C. The MgO(100) substrate was set at the position perpendicular to the target. From the results of X-ray photoelectron spectroscopy, we found that the BRBO films prepared at the Tsub from RT to 450°C contained Ba, Rb, Bi and O. In addition, X-ray diffraction results indicated that the films were (100) and (110)-oriented.

Fumihiko Toda; Tomoyuki Yamada; Satoru Kishida; Heizo Tokutaka

The In/BRBO/STO specimens were fabricated by depositing Ba0.6Rb0.4Bi1.0Oy (BRBO) on the SrTiO3 (STO) substrates by means of molecular beam epitaxy using 100% pure ozone and then, by depositing In metal. From the X-ray photoelectron spectroscopy results, we found that the In metal deposited on the BRBO/STO specimen removed the oxygen from BRBO and produced InOx layer at the interface between In metal and BRBO.

Fumihiko Toda; Tomoyuki Yamada; Katsufumi Hashimoto; Hitoshi Abe

A three terminal device with the Al/Al 2 O 3 /(Ba, Rb)BiO 3 /Nb-doped SrTiO 3 structure was fabricated using a superconducting base layer. The stable interface between (Ba, Rb)BiO 3 and the artificial oxide barrier was obtained using in situ AL 2 O 3 deposition. The output characteristics were measured as functions of input current. A current gain greater than 2 was obtained in the common emitter configuration.

Hiroyuki Naoe; Yuzuru Mitani; Toshiyuki Kitagawa; Satoru Kishida; Fumihiko Toda; Heizo Tokutaka

Hiroyuki Naoe; Yuzuru Mitani; Satoru Kishida; Fumihiko Toda; Heizo Tokutaka

Fumihiko Toda; Tomoyuki Yamada

Fumihiko Toda; Tomoyuki Yamada; Katsufumi Hashimoto; Hitoshi Abe