Effect of YBCO film characteristics on RF properties of MSL resonators with these films
- PDF / 1,770,625 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 35 Downloads / 162 Views
Effect of YBCO film characteristics on RF properties of MSL resonators with these films Kazunori Yamanaka, Akihiko Akasegawa, and Teru Nakanishi Inorganic Materials and Polymers Laboratory, Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0197, JAPAN.
ABSTRACT The effect of YBCO film characteristics on the RF properties of microstrip-line (MSL) resonators using two surface resistance Rs value types of films was investigated in terms of weak links. The films were characterized in both cystallinity and microstructure. The RF properties of the resonators were measured at frequencies of about 2 GHz. It was understood that the film samples with higher Rs at 70 K, which exhibited strong c-axis orientation, both the 90 and 45- degree angle grains in plane of the films,Y211 segregation, and porous structures show large influence on RF magnetic field dependence of normalized resonant frequency-shift ∆fc/fc, compared with the lower Rs type. On the other hand, the films with lower Rs at 70 K had much stronger c-axis orientation, the 90-degree angle grains, and dense structures. Consequently, it was considered that the lower Rs type films possessed fewer weak-links compared with the higher Rs type films, suggesting that the misorientation in the higher Rs films result in weak-links.
INTRODUCTION In microwave and/or RF devices such as resonators and filters, HTS (high-temperature superconducting) devices are attractive to have a merit of high Qu (Qu: unloaded Q) value, compared with the normal-conductor device with the same device structure [1,2]. To obtain higher Qu value in micostrip-line (MSL) devices, HTS films with lower Rs (Rs: surface resistance) have been commonly used. To attain lower Rs, it is essential that HTS films possess good crystal-orientation and fewer weak-links in the films [3,4]. In the case of a weak link structure, supercurrent with phase shift of Cooper pairs wave flows in superconducting crystals across the link, which is of thin barrier material or boundary (coupling grains) [5-7]. With this RF model, Rs is increased by the weak links, and inductance increases as increasing supercurrent [5-7]. According to this model, RF properties depend on film characteristics, which are governed by the weak links. Therefore, to obtain a higherunloaded Qu value, the relationship between film characteristics and weak-links needs to be well understood in the actual HTS devices. On the other hand, we previously reported [8] on film-thickness dependence of Qu of fabricated MSL resonators with YBCO (which mainly consists of YBa2Cu3OX, where X=6~7) films using two-type growth conditions. In this work, we investigated the effect of the film characteristics on the weak-links in RF properties of the MSL resonator devices by using the YBCO films.
II6.2.1
EXPERIMENT YBCO films were deposited on both sides of MgO(100) substrates by pulsed laser deposition using a KrF excimer laser[8]. Next, hairpin-type MSL resonators with the YBCO films were fabricated for the measurement of microwave properties. Qu
Data Loading...
