Table of Contents
NbN
NbN is a strong pinning superconductor with a relatively high Tc.
Sputtering
NbN can be reactively sputtered by adding N2 to the sputtering gas.
- Links to papers about the hysteresis loop of reactive sputtering come here
- Links to papers about reactive NbN sputtering go here
- Links to papers about physical properties of NbN go here
Z-400
In the Z-400 2 recipes are in use for sputtering NbN: Gertjan uses 1.7 kV and blend, Olaf uses 1.0 kV and no blend. See the Z-400 page for details.
UHV
Details about sputtering NbN in the UHV system go here.
Deposition rates
There is a systematic difference in X-ray and RBS thickness. Fitted composition makes sense and scatter yield make sense, it seems that (nuclear) collision crosssection and (electronic) stopping exponent are calculated OK. RUMP uses the wrong density, so the following procedure should be used:
- Fit the thickness t in /cm2
- Area nuclear density a = t * 1e15
- Thickness = a/d where d = atomic density
The density of Nb is 8.57 g/cm2, the density of Nb1N1 is 8.47 so the density of NbxN1-x can be assumed to be 8.52 with an accuracy < 1% for x between 1 and say 0.45. Therefore, the following algorithm can be used for calculating the thickness (gnuplot):
atpercm2=471e15 # whatever RUMP fit gives rho=8.52 n_a=6.022e23 m_nb=92.906 m_n=14.007 molmass(x)=x*m_nb+(1-x)*m_n atpercm3(x)=n_a*rho/molmass(x) cm(x)=atpercm2/atpercm3(x) nm(x)=cm(x)*1e7 set term postscript color set xrange [0.45 to 1] set title "NbxN1-x thickness sample 'Gertjan2'" set xlabel "composition" set ylabel "thickmess (nm)" plot nm(x)
The result is shown below:
So for the fitted composition Nb0.6N0.4 the thickness is 55 nm (57 X-ray)