Erbium (III) nitrate pentahydrate Er(NO3)3*5H2O was used as erbium precursor for the growth of Er and Ge added steam oxidized silicon layers by aerosol CVD, which
are used for the manufacturing of planar waveguides for optical applications [i]
[i] A.H. Kilian, J.B. MacChesney, T.F. Morse - US Patent 5,622,750, 1997, « Aerosol process for the manufacture of planar waveguides »