Electric field effect in Sm/sub 1-x/Ca/sub x/Ba/sub 2/Cu/sub 3/O/sub y/ bicrystal junctions

Abstract

A bstract-A three terminal device was fabricated by depositing a thin film of Ca-doped SmBa2Cu30y on a bicrystal SrTi03 substrate and then structuring a gate over the resulting junction.The channel shows RSJ-like Josephson junction behavior. By applying a voltage to the gate, a large electric field effect was observed. The largest field effect was observed in films where 30% of the Sm was replaced by Ca. The critical current of the junction was modulated 23% by the application of an electric field of 5~1 0~ V/cm. This electric field is about 100 times smaller than the electric field necessary for the field effects observed in homogeneous films. The sign of the field effect is consistent with that expected for a carrier-depleted grain boundaky region.

Electric field controllable Josephson junctions of high quality in high-T c superconductors

“…Furthermore gated Josephson junctions can be used as Josephson field-effect transistors ͑JOFETs͒. Dong et al 6 and Peterson et al 7 fabricated bicrystal JOFET devices using, like Ivanov, a metal-insulator-superconductor FET ͑MISFET͒ structure, but with underdoped Sm 1Ϫx Ca x Ba 2 Cu 3 O y and ultrathin YBCO films as superconducting channels, respectively. 2 In recent years, high-T c superconductors have been used for the fabrication of JOFETs.…”

Ginzburg–Landau theory of Josephson field effect transistors

“…Our aim in this paper is to apply this method to the field efffect modulations seen in the JoFETs of Ref. [3,4]. We demonstrate that the JoFET systems can be fit into the same conceptual framework as the YBa 2 Cu 3 O 7−δ grain boundaries.…”

“…Dong et al [3,4] showed that there is a 23% modulation of the critical current on a grain boundary of a 50 nm thick channel of Sm 1−x Ca x Ba 2 Cu 3 O y (Ca-SBCO). Nakajima et al [7] reported a 5% modulation of critical current on a 60 nm thick YBCO grain boundary junction channel which can be described by a parallel resistor model.…”

“…The experimental measurements [3] were taken on hole-overdoped Ca-SBCO bicrystal Detailed work on the effect of doping on the critical temperature of the cuprates [12,13] shows that T c follows a parabolic relation: T /T c,max = 1 − 82.6 * (n − 0.16) 2 , where n is the carrier concentration (holes per CuO 2 unit) and T c,max = 70K for the material under study (Ca 0.3 Sm 0.7 Ba 2 Cu 3 O y ) [3]. From the specific characteristics of the specimen, given that a grain boundary of 24 0 corresponds to a weakly-coupled bicrystal, then the dependence of the concentration n on the distance follows an exponential function in accordance with the previous work [9].…”

“…There are many different directions that have been investigated: the electric field effect transistor, the flux-flow transistor, quasiparticle injection devices, etc. The superconducting field effect transistors (suFETs) with a homogeneous thin film channel [1,2] and JoFETs with a Josephson junction channel [3][4][5][6][7][8] are electric field related devices. In general, the required electric field for the field effect in JoFETs is orders of magnitude smaller than the field required in suFETs with homogeneous thin film.…”