Epitaxial Deposition of Niobium Nitride by Sputtering

Abstract

Single crystal films of niobium nitride on MgO single crystals cleaved in air have been prepared by dc sputtering technique in argon with addition of a small amount of nitrogen gas. Deposition rate, substrate temperature, discharge pressure and substrate-cathode spacing have been varied, and dependence of superconducting transition temperatures and structural characteristics of films on these parameters has been studied. Single crystal films were formed with (100) [110]NbN//(100) [110]Mgo. Epitaxial temperature was lowered by shortening the substrate-cathode spacing and by lowering the discharge pressure. The above results are discussed in terms of the effect of arrival energy of the sputtered atoms at the substrate. It was shown that there existed a high temperature limit for the formation of single crystal films. The highest transition temperature of the single crystal was 16.5 K and its width of the transition was 0.08 K.