|Budget Amount *help
¥12,500,000 (Direct Cost : ¥12,500,000)
Fiscal Year 1999 : ¥3,900,000 (Direct Cost : ¥3,900,000)
Fiscal Year 1998 : ¥8,600,000 (Direct Cost : ¥8,600,000)
The purpose of this study is to fabricate a tunable GHz-THz generator working at high temperatures on an experimental basis, which utilizes natural superlattices of intrinsic Josephson junctions, which consist of superconducting CuOィイD22ィエD2 and insulating BiO/SrO layers, in layered high-temperature oxide-superconductor BiィイD22ィエD2SrィイD22ィエD2CaCuィイD22ィエD2OィイD2yィエD2 single crystals.
The results obtained in this study are as follows :
1. A system for operating and measuring the generator has been prepared using a refrigerator, which can cool it down to 4.2K from 300K.
2. Rectangular mesas (superlattices) as generators have been fabricated on an experimental basis from the single crystals (with transition temperatures of 〜 85K), by using photolithography and ion etching.
3. The mesas have shown that on their operations, the coherent motion of flux quanta (Josephson vortices) occurs at high rates of (1-5) ×10ィイD1-6ィエD1m/s in them at 4.2K, which correspond nearly to the highest phase velocity of electromagnetic waves induced in the constituent intrinsic Josephson junctions, while at 77K, it occurs at similar high rates in the mesas with less than 20 intrinsic Josephson junctions but at much lower rates in those with more junctions.
4. The mesas have shown that the frequencies of oscillations, which take place due to the motion of flux quanta at the high rates in them, can be controlled to linearly with external magnetic fields, and then an oscillation of 80GHz occurs with a magnetic field of 0.16T.
5. The mesas have shown that the coherent motion of electronic (hole) waves in the intrinsic Josephson junction superlattices can be excited and controlled by current pulses, so as to generate high frequency oscillations of several ten GHz-THz.