Pulsed Laser Deposition of NbNx (0 ≤ x ≤ 1.4) Thin Films

ABSTRACTThe structure, morphology, and electrical properties of pulsed laser deposited NbNx (0 ≤ x ≤ 1.4) thin films have been investigated. Films were deposited from Nb metal targets on oriented MgO (100) and amorphous fused silica substrates as a function of substrate temperature and ambient pressure. A reducing atmosphere (N2 with 10% H2) was used to prevent oxide formation. At elevated temperatures, the N/Nb ratios of films deposited on MgO, as determined from Rutherford Backscattering Spectroscopy, increased from 0 −1.4 as the ambient pressure was varied from vacuum to 200 mTorr, respectively. NbNx films (x=l) were deposited at 600 °C and 60 mTorr. Both the structure and electrical properties of the deposited films varied strongly with the substrate type. On fused silica, NbN films were poorly crystalline with low critical temperatures (Tc ∼ 8 – 11 K) and low critical currents (Jc (4.2 K) ∼ 2 MA/cm2), whereas on MgO the NbN films were oriented and had better transport properties (Tc ∼ 16.4 K and Jc (4.2 K) = 7.1 MA/cm2).