High-Tc superconducting THz emitters fabricated by wet etching

Abstract

We studied the etching of small crystals of the high-Tc superconductor Bi2Sr2CaCu2O8+δ (Bi2212) with various dilute compositions of hydrochloric and nitric acids. A particular mixture of those acids was chosen to simultaneously fabricate multiple rectangular stand-alone Bi2212 mesa structures from a large, doubly-cleaved and doubly metallic-coated single crystal. The radiation characteristics of these devices were found to be very similar to stand-alone devices fabricated previously using dry-etching techniques. The greatly reduced time and cost of fabrication of stand-alone Bi2212 devices using our wet-etching technique should facilitate the mass production of a large number of identical stand-alone devices from a large single-crystalline Bi2212 substrate.

Approaches to High Performance Terahertz-Waves Emitting Devices Utilizing Single Crystals of High Temperature Superconductor Bi₂Sr₂CaCu₂O_8+δ

“…The heating generated in the process of ion-milling would affect the oxygen contents of the crystals. Recently, in order to improve the problems, we developed a wet etching method to make the Bi2212 crystal chips [39], [40]. We studied the etching characteristics of solutions which are mixture of HCl and HNO 3 .…”

Investigation of wet etching solutions and method for thicker stand alone type of mesa structures of Bi2212 single crystals

“…First of all, we will briefly describe the fabrication process of SAMs by the wet etching method as reported in our previous study. 37) A piece of Bi2212 single crystal grown by TSFZ-method 38) with a thickness of about 3-4 μm was obtained by cleaving the crystals using a Scotch tape. Both cleaved surfaces are coated by metallic thin films of Ag and Au by evaporation.…”

“…41) Furthermore, we reported that the undercut of mesa structures can be reduced by using a mixture solution of HNO 3 and HCl. 37) A wet etching method investigated here is based on the above previous studies and is applicable to the thicker SAMs up to roughly 10 μm. We evaluated four solutions with a higher concentration of HCl against our previous study 37) as shown in Table I and tried to find an appropriate one to make thicker SAMs.…”

“…These properties are predicted theoretically 34,35) and confirmed experimentally. 16,19,23,36) In the previous studies, SAMs are fabricated by using dry 16,19,23,36) and wet 37) etching methods. We reported a wet etching method of SAMs with a thickness of around 3 μm previously.…”

“…We reported a wet etching method of SAMs with a thickness of around 3 μm previously. 37) A thicker mesa structure is expected to obtain stronger emission power. We developed etching solutions for thicker SAMs.…”