Growth of PAMBE grown TiN//AlN//TiN Josephson junctions

In the pursuit of epitaxially grown Josephson Junction (JJ) creation, this work investigates the growth of TiN//AlN//TiN tri-layer heterostructures. This material stack offers several benefits over traditional Al//AlO_x//Al JJs. These include enhanced mechanical stability, potentially reduced two level system loss (TLS) due to the use a crystalline AlN barrier, and higher superconducting critical temperature, which may reduce the number of thermally excited quasiparticles. This work will be presented in two parts: materials development and growth of the tri-layer structure, and a separate presentation covering the device fabrication and electrical characteristics of the finished device.

Plasma Assisted Molecular Beam Epitaxy (PAMBE) grown TiN and AlN samples were grown on Si (111) and Al₂O₃ (0001) to optimize growth parameters for surface roughness, crystallinity, and compositional uniformity. Notably, the transition points of AlN and TiN from nitrogen rich to metal rich is clearly identified using HRXRD, AFM, and EDX.  Structural analysis of the JJ trilayer structures on both substrates will be discussed.