학술논문
Study on the effect of Bi/Sr ratio on the device characteristics of high-Tc superconducting terahertz wave emitters made of Bi2 Sr2 CaCu2 O8+δ single crystals.
Document Type
Article
Author
Source
Subject
*SUPERCONDUCTING transition temperature
*SINGLE crystals
*SUBMILLIMETER waves
*JOSEPHSON junctions
*HIGH temperature superconductors
*CRYSTAL defects
*CUPRATES
*SUPERCONDUCTING transitions
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Language
ISSN
0021-8979
Abstract
To obtain high-performance THz-wave-emitting devices made of single crystals of Bi 2 Sr 2 CaCu 2 O 8 + δ (Bi2212), a high-temperature superconductor, an understanding of the device characteristics based on crystal characteristics can be a key issue because, in principle, the electrical properties of the intrinsic Josephson junctions (IJJs) constructed in Bi2212 crystals highly depend on crystal conditions, such as carrier concentration, crystal homogeneities, and crystal defects. To evaluate the tendencies of the device characteristics associated with crystal characteristics, we prepared Bi2212 crystals with different Bi/Sr ratios (x = 0.05 , 0.15, and 0.25) and δ values (annealed under N 2 or O 2 gas flow conditions). The unit cell parameter c decreased as the Bi/Sr ratio or δ increased. For the same annealing conditions under N 2 gas flow, the superconducting transition temperature as well as the size of the hysteresis loop of the current–voltage characteristics and emission characteristics were significantly suppressed for the sample with x = 0.25 compared with the corresponding values for the samples with x = 0.05 and 0.15. The experimental results clearly indicate that parameters, such as the Bi/Sr ratio and annealing conditions, are crucial factors in determining the electrical characteristics of a device. This information can be a useful guide for the preparation of crystals for IJJ THz-wave devices that can be fine-tuned according to the desired device characteristics. [ABSTRACT FROM AUTHOR]