M.Sc Thesis

M.Sc StudentXing Xinxi
SubjectHigh Tc Superconductor Nanoscale Device
DepartmentDepartment of Electrical and Computer Engineering
Supervisor ASSOCIATE PROF. Alex Hayat
Full Thesis textFull thesis text - English Version


Superconductors have enormous potential for applications in various fields due to their unique properties such as zero-resistance and the Meissner effect.  In particular, superconductor integrated devices, such as superconducting nanowire single photon detectors (SNSPDs) and superconducting micro-strip RF components, are important driving forces of the development in experimental quantum optics and communication technologies.

Existing SNSPDs based on low-Tc superconducting materials, such as NbN, Nb, NbSi offer very broadband wavelength detection range and very fast response times on the ps scales. However, they require liquid He cooling down to ~5K, preventing practical applications outside scientific labs, due to bulky equipment and very high costs. The possible application of high-Tc superconductors (HTSs) to implement SNSPDs is challenging, but also promising. Especially copper oxide superconductors show a Tc higher than boiling point of liquid nitrogen (77K), paving the way for portable and cheap single-photon detection technology. Nevertheless, the fabrication of high-Tc nanowires remains a challenge - due to the difficulty in obtaining high-quality uniform films due to the complex structure of the materials and their chemical instability.

In our research, several different directions were studied for fabrication methods of YBa2Cu3O7-x (YBCO) nanowires for photon detection. We developed a robust YBCO nanowire fabrication method through selective epitaxial growth (SEG) and demonstrated its the electrical and optical properties, showing high photodetection efficiency. We provide a solution for the superconducting degradation problem often encountered in the fabrication of ultra-narrow nanowires, and open a route to single photon detection based on ultrathin high temperature superconductor. Moreover, we started investigating YBCO nanowire based RF components.