Highly dense amorphous Nb2O5 films with closed nano-sized pores

This study is focused on tailoring Nb2O5 film porosity during reactive pulsed magnetron sputtering. Dense amorphous films with closed nanopores have been formed onto unheated substrates at high growth rates. The films have a high refractive index n_400=2.54, a low extinction coefficient, k_400~6x10^-4, a low mechanical stress (-90 MPa) and a negligible thermal shift. The specific depth distribution of the nanopores is believed to be the reason for the high film density combined with a low mechanical stress.