CVD (Chemical Vapor Deposition) is a technique for thin film deposition. In this image, unlike as usual, niobium nitride grew as whiskers. This forest of whiskers is superconducting. And even if it has no application currently, its nano scale gives it a particular affinity for oxygen and therefore a high surface energy.
About the author: Manoël Jacquemin is a PhD student in the TOP group studying ultrathin niobium nitride films obtained by CVD.