Investigation of the superconducting properties of NbN films deposited by DC magnetron sputtering on a high-k dielectric HfO2 buffer layer

Abstract

The influence of the buffer layer of hafnia dielectric (HfO2) on the superconducting properties of niobium nitride films (NbN), produced by the technique of reactive magnetron depositing has been investigated for the first time. This study presents a comprehensive analysis of morphological, microstructural, and electrophysical parameters of thin NbN films. The dependence of transition critical temperature on the thickness of the HfO2 buffer layer has been obtained. For the first time, it has been demonstrated that the superconducting properties of niobium nitride films at the HfO2 buffer layer have high superconductive parameters, namely, T c ∼ 13 K (with a the film thickness of approximately 30 nm) and high critical current density of approximately 107 A cm−2. The relation between the thickness of the HfO2 buffer layer with the critical current density of niobium nitride films has been determined. It appeared that the values of critical current density increase significantly up to 13 MA cm− 2 when the thickness of the hafnia buffer layer is more than 2 nm.