Fabrication of superconducting niobium nitride nanowire with high aspect ratio for X-ray photon detection

Shuya Guo,Hang Han,Xiaomin Bei,Qi Chen,Guanglong He,Danfeng Pan,Xuecou Tu,Xiaoqing Jia,Peiheng Wu,Qingyuan Zhao,Labao Zhang,Feiyan Li,Jian Chen,Lin Kang,Yaojun Wu,Hengbin Zhang,Jun Xie

doi:10.1038/s41598-020-65901-5

Shuya Guo, Hang Han + Show 15 more

Open Access

https://doi.org/10.1038/s41598-020-65901-5

Copy DOI

Abstract

The niobium nitride (NbN) nanowires fabricated with the high-quality ultra-thin NbN film with a thickness of 3 nm–6 nm were widely used for single photon detectors. These nanowires had a low aspect ratio, less than 1:20. However, increasing the thickness and the aspect ratio of highly-uniformed NbN nanowires without reducing the superconductivity is crucial for the device in detecting high-energy photons. In this paper, a high-quality superconducting nanowire with aspect ratio of 1:1 was fabricated with optimized process, which produced a superconducting critical current of 550 μA and a hysteresis of 36 μA at 2.2 K. With the optimization of the electron beam lithography process of AR-P6200.13 and the adjustion of the chamber pressure, the discharge power, as well as the auxiliary gas in the process of reactive ion etching (RIE), the meandered NbN nanowire structure with the minimum width of 80 nm, the duty cycle of 1:1 and the depth of 100 nm were finally obtained on the silicon nitride substrate. Simultaneously, the sidewall of nanowire was vertical and smooth, and the corresponding depth-width ratio was more than 1:1. The fabricated NbN nanowire will be applied to the detection of soft X-ray photon emitted from pulsars with a sub-10 ps time resolution.

Highlights

The niobium nitride (NbN) nanowires fabricated with the high-quality ultra-thin Niobium nitride (NbN) film with a thickness of 3 nm–6 nm were widely used for single photon detectors
Through Geant[4] simulations, we obtained that the X-ray photon absorption of the 10 nm thick NbN film for 1 keV and 6 keV was only 3.69% and 0.23%, respectively[9], and the superconducting nanowire single-photon detectors (SNSPDs) prepared with the ultra-thin NbN film was unable to effectively detect high-energy single photons
The well-known Bosch process in deep reactive ion etching (DRIE) technology is widely used in high aspect ratio silicon etching

Summary

Introduction

The niobium nitride (NbN) nanowires fabricated with the high-quality ultra-thin NbN film with a thickness of 3 nm–6 nm were widely used for single photon detectors. These nanowires had a low aspect ratio, less than 1:20. Development, Reactive ion etching, Degumming; (b) TEM image of ultra-thin NbN nanowire with the aspect ratio of about 1:20; (c) Superconducting transition temperature(Tc) is 11.2 K for NbN film with thickness of 100 nm, which grows on Silicon substrate with a Si3N4 layer, and the superconducting transition width(ΔT) is 0.24 K

Methods

Conclusion