Strain, interdiffusion, and microstructural evolution under ion irradiation in Ni(111)/Mo(110) multilayers: Interdependence with elastic properties
- Laboratoire de Metallurgie Physique, UMR CNRS 6630, Universite de Poitiers, SP2MI, Av. M. et P. Curie, BP 30179, 86962 Futuroscope-Chasseneuil Cedex (France)
The interdependence between the microstructure of sputter-deposited Ni(111)/Mo(110) superlattices and their elastic behavior is investigated as a function of the bilayer period ({lambda}). Brillouin light scattering measurements show that a drastic softening of the effective shear modulus occurs with decreasing {lambda}, until {lambda}=2 nm where it reaches -62%. Ion irradiation is here used to trigger stress relaxation and to induce, in a controlled way, interdiffusion and structural changes allowing us thus to investigate their influence on the elastic anomaly. At a very low irradiation dose (0.1 displacements per atom), the relief of the lattice expansion and associated compressive stresses does not induce any change of the elastic response, which indicates that the elastic behavior of the as-grown multilayers is not correlated with the presence of elastic strains. Furthermore, a detailed x-ray diffraction analysis shows that the unstrained lattice parameter of Mo layers exhibit a linear dependence with the interface density, while the Ni unstrained lattice parameter remains nearly unchanged in the same {lambda} range. This effect can be attributed to an interfacial mixing of a constant Ni amount ({approx}1.5 monolayers) into the Mo layers, as a consequence of a dynamic segregation of Ni atoms during growth. Thus, the formation of interfacial metastable and supersaturated solid solutions, structurally and mechanically unstable, appears as the origin of the huge elastic softening observed in this system. At high ion fluences, when the mixing process becomes dominant, the present study also provides experimental data on phase transformation in 'driven' alloys, by addressing the issue of the stability of out-of-equilibrium structures under irradiation.
- OSTI ID:
- 20665073
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 71, Issue 4; Other Information: DOI: 10.1103/PhysRevB.71.045422; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRYSTAL STRUCTURE
ELASTICITY
EXPERIMENTAL DATA
ION BEAMS
IRRADIATION
LATTICE PARAMETERS
LAYERS
LIGHT SCATTERING
MICROSTRUCTURE
MOLYBDENUM
NICKEL
PHASE TRANSFORMATIONS
RADIATION DOSES
SOLID SOLUTIONS
SPUTTERING
STRAINS
STRESS RELAXATION
STRESSES
SUPERLATTICES
SURFACE COATING
X-RAY DIFFRACTION