Preparation and Superconducting Properties of Thin Films of Transition Metal Interstitial Compounds

Abstract

The importance of geometrical parameters in determining the superconducting properties of a material has recently been a topic of considerable theoretical interest. Experimental investigation in this area so far has been restricted principally to thin-film structures of the non-transition elements, compared of materials possessing relatively small superconducting non-parameters (K). In this paper we discuss some recent studies on thin-film structures of transition metal compounds having both high critical temperatures (Tc≳14 °K) and large upper critical fields (Hc2≳100 kOe). The materials in this work have the rocksalt structure (B1) and are based upon the compound niobium nitride, NbN. The films were prepared by reactive sputtering in argon-nitrogen atmospheres in an ultrahigh vacuum system with a background pressure ≲5×10−10 Torr. Variation of the nitrogen partial pressure over the range 10−3 to 10−6 Torr was used to obtain different film compositions.