Materials Study of NbN and TaxN Thin Films for SNS Josephson Junctions

Properties of NbN and Ta
_x
N thin films grown at ambient temperatures on SiO
₂
/Si substrates by reactive-pulsed laser deposition and reactive magnetron sputtering (MS) as a function of N
₂
gas flow were investigated. Both techniques produced films with smooth surfaces, where the surface roughness did not depend on the N
₂
gas flow during growth. High crystalline quality, (111) oriented NbN films with T
_c
up to 11 K were produced by both techniques for N contents near 50%. The low temperature transport properties of the Ta
_x
N films depended upon both the N
₂
partial pressure used during growth and the film thickness. The root mean square surface roughness of Ta
_x
N films grown by MS increased as the film thickness decreased down to 10 nm.