Superconducting and normal properties of NbN produced by ion implantation of niobium thin films

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:6461965

Johnson, J P

Niobium films (120 nm thick) deposited by electron beam evaporation were implanted near 5K with 100 keV N/sub 2//sup +/ ions to maximum fluences of 4 to 7 x 10/sup 17/ N/cm/sup 2/. STEM diffraction patterns showed a structural phase transformation from the initial Nb lattice with (110) fiber texture (bcc, a/sub 0/ = 3.30 A) to randomly oriented delta-NbN (fcc, a/sub 0/ = 4.35-4.39 A), via an intermediate, highly disordered Nb-(interstitial N) structure (bcc, maximum a/sub 0/ = 3.42 A). Decreases in transition temperature T/sub c/ from 9 K to a minimum of 3K, and rapid linear increases in residual resistivity rho/sub 10/, were observed to fluences of 1.0-1.5 x 10/sup 17/ N/cm/sup 2/, and were attributed to the accumulation of radiation-induced defects. Continued implantation resulted in delta-NbN formation and T/sub c/ increases to maximum values of 9-10 K which were achieved at fluences from 3.5 to 5.0 x 10/sup 17/ N/cm/sup 2/, corresponding to average substoichiometric N/Nb ratios of 0.52-0.75, at which point the phase transformation was complete. The delta-NbN formation was accompanied by significant lattice reordering and grain growth. At higher fluences, gradual T/sub c/ declines (by 1-2 K), and the sharp rises in rho/sub 10/, were observed, possibly due to film sputtering. Large reductions in flux pinning force density to fluences which produced minimum T/sub c/ values (about 1 x 10/sup 17/ N/cm/sup 2/) were attributed to the destruction of strong grain boundary pinning centers by the ion bombardment.

• Research Organization: Florida State Univ., Tallahassee (USA)
• OSTI ID: 6461965
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
360106 -- Metals & Alloys-- Radiation Effects
640301 -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CATIONS
CHARGED PARTICLES
COLLISIONS
DATA
DEPOSITION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
ENERGY BEAM DEPOSITION
EXPERIMENTAL DATA
FILMS
INFORMATION
ION IMPLANTATION
IONS
METALS
NIOBIUM
NIOBIUM COMPOUNDS
NIOBIUM NITRIDES
NITRIDES
NITROGEN COMPOUNDS
NITROGEN IONS
NUMERICAL DATA
PHYSICAL PROPERTIES
PHYSICAL RADIATION EFFECTS
PNICTIDES
RADIATION EFFECTS
REFRACTORY METAL COMPOUNDS
SUPERCONDUCTIVITY
SURFACE COATING
THERMODYNAMIC PROPERTIES
THIN FILMS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TRANSITION TEMPERATURE