Techniques for enhancing the PLD growth of superconducting YBCO thin films

[摘要] ENGLISH ABSTRACT: High Temperature Superconductors (HTS) exhibit exceptional electrical properties that make themattractive candidates for numerous electronic devices and applications. However, constructingworking devices can be challenging due to fabrication difficulties of these brittle ceramics. Thisthesis investigates new methods to make the fabrication of high quality YBa2Cu3O7 (YBCO) thinfilms easier and compatible with more materials.We present the development of a universal add-on method that can be used in situ to improve thequality of superconducting thin films deposited by Pulsed Laser deposition (PLD). We investigatethe in situ application of electric fields and voltage biasing to improve the thin film growth. Consideringvarious electrode configurations, we have developed a final electrode design that is stableand produces reproducible results. By introducing an insulated high voltage (HV) electrode into thechamber during deposition, the quality of the deposited thin films can be modulated depending onthe polarity of the voltage applied. Applying a positive voltage improves the film quality obtained.Applying a negative voltage degrades the superconducting properties of the films.A simple proof-of-concept HTS dual-mode microwave filter was designed, fabricated and tested.Only the filter produced using our novel PLD technique displayed the correct filtering action uponcooling to 77K. This is attributed to the thin films better superconducting properties due to ourdeveloped technique.

[发布机构] Stellenbosch University