Method of producing high T.sub.c superconducting NbN films
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorsSarita Thakoor, James L. Lamb, Anilkumar P. Thakoor, Satish K. Khanna
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Abstract
Thin films of niobium nitride with high superconducting temperature (T.sub.c) of 15.7.degree. K. are deposited on substrates held at room temperature (.about.90.degree. C.) by heat sink throughout the sputtering process. Films deposited at P.sub.Ar >12.9.+-.0.2 mTorr exhibit higher T.sub.c with increasing P.sub.N2,I, with the highest T.sub.c achieved at P.sub.N2,I =3.7.+-.0.2 mTorr and total sputtering pressure P.sub.tot =16.6.+-.0.4. Further increase of N.sub.2 injection starts decreasing T.sub.c.
Claims6
A method for forming NbN films having a high T.sub.c in the range of 15.degree. to 16.degree. K. and possessing B1 crystal structure with a (111) texture, without the introduction of carbon or any compound of carbon in any form to obtain the B1 crystal structure and high T.sub.c characteristics, by dc reactive magnetron sputtering niobium on a substrate in a reactive gas mixture of high purity Ar and N.sub.2 and a base pressure of 10.sup.-8 Torr comprising the steps of
- maintaining said substrate at about 20.degree. C. throughout the sputtering process,
- maintaining the partial pressure P.sub.N2,I of reactive gas, N.sub.2, constant in a range of 3 to 4 mTorr,
- maintaining the partial pressure P.sub.Ar of the carrier gas, Ar, constant in a range of 12.9 to 17 mTorr, and
- maintaining the total sputtering pressure constant in a range of 16 to 21 mTorr.
Dependencies are inferred from the claim text.