Preparation And Performance Research Of Porous NbN Films

The breakthrough discovery of superconductivity has opened up a whole new range of applications in the low-temperature range,and various new superconducting materials can be used to prepare superconducting detectors that have unique advantages in many applications.The core of superconducting nanowire single-photon detectors is an ultra-thin nanowire prepared from low-temperature superconducting materials,which detects single photons by receiving photons and generating a local resistance region.Superconducting nanowire single-photon detectors have been developed rapidly and comprehensively due to their high detection efficiency,low dark count and wide response spectrum,and have been widely used in quantum information fields such as quantum communication and quantum computing,and in photodetection technologies such as biophysics.The superconducting materials for the preparation of superconducting nanowire single photon detectors are mainly niobium nitride(Nb N)materials,and the properties of Nb N films have a decisive influence on the performance parameters and quality of the devices,thus the exploration of Nb N films is crucial.In addition,it has been shown that the introduction of nanoporous array structures in raw materials may lead to some new phenomena and properties,and similarly,the porous structure has an effect on the properties of superconducting materials.In this paper,we prepare high-quality niobium nitride films by magnetron sputtering and construct nanoporous structures on the films to investigate the effects of porous structures on the films and to study the properties of porous niobium nitride nanowires,expecting to use the porous nanowires in superconducting nanowire single-photon detectors to enhance their performance.The main contents of this paper are as follows.First,in this paper,RF magnetron sputtering with an oblique target tilt angle of 27°is adopted for sputtering deposition of niobium nitride films on single-crystal polished Mg O substrates.After exploring the effects of the basic process parameters such as substrate temperature,power,nitrogen-argon ratio and working air pressure on the film properties and analyzing the characterization results of the niobium nitride film,the optimal parameters for the preparation of niobium nitride film were obtained: substrate temperature of 650°C,power of 100 W,nitrogen-argon ratio of 15:30sccm,background vacuum of 4×10-4 Pa,working air pressure of 0.28 Pa,and pre-sputtering for 40 min.For 40 min,the high-quality ultra-thin superconducting niobium nitride films were prepared.Next,the Nb N films prepared under the optimized conditions were further characterized and analyzed.The properties of the optimized Nb N films were characterized by means of X-ray photoelectron spectroscopy,scanning electron microscopy and low-temperature test system,and the crystal structure,composition and superconductivity of the films were verified.After the Nb N films were prepared under the optimized parameters,the porous anodic alumina was transferred to the surface of the films as a template,and reactive ion etching was adopted to etch the nanoporous array structure on the films to obtain porous superconducting Nb N films.Different porous niobium nitride films were prepared by varying the thickness of the Nb N film and the pore size of the porous holes,and the influence of the porous structure on the properties of the superconducting niobium nitride films was investigated by testing the performance parameters such as the superconducting transition temperature and resistance characteristics of the films.Finally,ultra-thin superconducting niobium nitride nanowires of 20 nm thickness were prepared,and ultra-thin superconducting porous niobium nitride nanowires of the same thickness were prepared using porous anodic alumina templates,and their properties were tested to study the effect of the porous structure on the nanowires,and the effect of the porous structure on the reduction of the effective width of the nanowires was verified to obtain a nanowire structure that meets the application range of superconducting nanowire single photon detectors.