EN
We report a detailed study on control of sputtering parameters
for synthesizing NbN superconducting thick films. The NbN
films are deposited on single crystalline silicon (100) by DC
reactive sputtering, i.e., deposition of Nb in the presence of
reactive N2 gas. After several runs, samples were prepared
with Ar:N2 partial gas ratios of 90:10, 80:20 and 70:30 for a
deposition time of 10 minutes. The fabricated films (400 nm
thick) crystallize with a cubic structure, with a small quantity
of Nb/NbOx embedded in the main NbN phase. All three
samples are characterized by scanning electron microscopy
(SEM) and energy dispersive X-ray spectroscopy (EDAX),
to examine their microstructure and elemental compositional
distributions, respectively. The roughness was mesured by
atomic force microscopy (AFM). The optimized film prepared
with Ar:N2 gas ratio of 80:20 has a Tc(R = 0) in zero and
140 kOe fields of 14.8 K and 8.8 K, respectively. The upper
critical field Hc2(0) of the studied superconducting films
is calculated from magneto-transport [R(T )H] measurements
using GL and WHH equations.