パルス電流法によるBi-2212接合スタックの接合数評価

摘要

Bi_2Sr_2CaCu_2O_x(Bi-2212)の特異な結晶構造に起因する固有Josephson接合を利用したテラへルツ発振に関する研究が精力的に進められている.我々は，素子作製の際に接合表面に劣化を伴わない利点をもつ両面加工法を用い内部接合スタック作製し，THz発振に関する研究を進めてきた.発振特性の理解には接合面積，接合数の評価が重要となる.本研究では，内部スタック構造をもつ固有ジョセフソン素子の接合数を見積もるためにパルス電流を用いた電流-電圧特性を行い，見積もられた接合数から発振特性について検討した.%Coherent THz emission from Bi_2Si_2CaCu_2O_(8+δ) intrinsic Josephson junction (Bi-2212 IJJ) with a large mesa type structure has been reported by several groups. We have studied fabrication process of a Bi-2212 IJJ oscillator on-chip coupled to a Bi-2212 IJJ detector by using a double-side patterning process without a surface degradation. It is very important to investigate the lateral dimension and the number of junctions of the IJJs stack in order to understand a mechanism of radiation from the Bi-2212 IJJs. In this study, we report a detailed study on pulse current method to estimate the number of junctions in the IJJs stack and consider an oscillation characteristic.