Superconducting properties of very high quality NbN thin films grown by high temperature chemical vapor deposition

TL;DR

This paper demonstrates that high-temperature chemical vapor deposition (HTCVD) can produce high-quality NbN thin films with a record superconducting transition temperature of 17.06 K below 50 nm thickness, showing promise for superconducting electronics.

Contribution

It introduces HTCVD as an effective method for growing high-quality NbN thin films with high $T_c$ and low disorder, surpassing previous growth techniques.

Findings

Achieved a $T_c$ of 17.06 K in NbN films below 50 nm

Reported lower disorder levels compared to previous methods

Demonstrated HTCVD's potential for high-quality superconducting films

Abstract

Niobium nitride (NbN) is widely used in high-frequency superconducting electronics circuits because it has one of the highest superconducting transition temperatures ($T_c$ $\sim$ 16.5 K) and largest gap among conventional superconductors. In its thin-film form, the $T_c$ of NbN is very sensitive to growth conditions and it still remains a challenge to grow NbN thin film (below 50 nm) with high $T_c$. Here, we report on the superconducting properties of NbN thin films grown by high-temperature chemical vapor deposition (HTCVD). Transport measurements reveal significantly lower disorder than previously reported, characterized by a Ioffe-Regel ($k_F$$\ell$) parameter of $\sim$ 14. Accordingly we observe $T_c$ $\sim$ 17.06 K (point of 50% of normal state resistance), the highest value reported so far for films of thickness below 50 nm, indicating that HTCVD could be particularly useful for growing high quality NbN thin films.