The variation of the properties of niobium nitride (NbN) thin films as a function of argon partial pressure and nitrogen flow were studied. The films were deposited by dc reactive planar magnetron sputtering onto unheated substrates. All of the films were superconducting and had the B1, face-centered cubic crystal structure. A number of films deposited at argon partial pressures of 5 and 7 mTorr had superconducting critical temperatures (Tc ) of 15.6 K and grain sizes of 100–120 nm. The film morphology showed a zone 1 to zone T transition as the argon partial pressure was decreased from 12 to 5 mTorr. Films deposited below 5 mTorr exhibited excessive tensile stress (>1.9×109 N/m2) and delaminated from the substrate.
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Westra et al. (1990) studied this question.