Comparison of Superconducting Transition Characteristics of Two Iridium/Gold Bilayer Transition Edge Sensor Devices

• Published in: Japanese Journal of Applied Physics 2004-05, Vol.43 (5R), p.2742
• Main Authors: Kunieda, Yuichi, Fukuda, Daiji, Ohno, Masashi, Takahashi, Hiroyuki, Nakazawa, Masaharu, Inou, Tadashi, Ataka, Manabu
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.43.2742

We are developing a high-energy-resolution X-ray microcalorimeter for X-ray fluorescent spectrometry using a superconducting transition edge sensor (TES) that consists of a bilayer of iridium and gold (Ir/Au). In this paper, we have studied the superconducting transition characteristics of two different bilayer structures. Type 1 is a simple stacked bilayer where a square-pattern film of iridium is covered with an identical pattern of gold. Type 2 is based on the Type 1 Ir/Au film, however, it has Au side banks. The resistance-temperature characteristics of these films are investigated by a four-wired resistance measurement method. As a result, the transition curve of Type 2 obeyed the Ginzburg–Landau (GL) theory; however, the transition curve of Type 1 was entirely different from that of Type 2. The reason there was a difference in these transition curves of the two devices is discussed in terms of the difference in the electric current distribution inside TESs. Even if we assume a uniform bilayer film and a uniform proximity effect over the entire film, the current density inside the device affects the characteristics of the transition curves.