The epitaxial growth of NbN films deposited on rf-sputtered MgO films have been prepared by rf-magnetron sputtering in N2/Ar atomosphere. These epitaxially growth films of (200)Mgo//(200)NbN orientation were formed on various kinds of substrates. The reactively sputtered NbN on MgO films had high critical temperature. The Tc value of NbN (25nm) /MgO (80nm) film is about 15.7 K. Also all-refractry Josephson tunnel junctions were formed without breaking vacuum, producing the epitaxially growth NbN/MgO/NbN sandwitch on MgO thin films on unoxidized Si substrate. The epitaxial junction has the high sum-gap voltage, and shows excellent I-V characteristics.
