Growth of single-crystal TiN/VN strained-layer superlattices with extremely high mechanical hardness

• DOI: 10.1063/1.339770
• Publication Date: 2002-07-26T12:53:52Z
• Authors: U. Helmersson; S. Todorova; S. A. Barnett; J.-E. Sundgren; L. C. Markert; J. E. Greene
• Keywords: Crystal (programming language)

Single-crystal TiN/VN strained-layer superlattices (SLS’s) with layer thicknesses lTiN =lVN =λ/2 (where λ is the period of superlattice) ranging from 0.75 to 16 nm have been grown on MgO(100 ) substrates by reactive magnetron sputtering. Cross-sectional transmission electron microscopy (TEM) and x-ray diffraction examinations showed that films were single crystals exhibiting coherent interfaces several orders superlattice reflections. There was no evidence in either plan-view or cross-sectional TEM analyses misfit interfacial dislocation arrays. The primary defects observed loops a diameter 8–10 extending through layers small 1–2 confined within layers. Microindentation hardness values H, measured as function total thickness 2.5 μm, increased 2035±280 kg mm−2 for Ti0.5V0.5N alloys (i.e., λ=0) reach maximum 5560±1000 at λ=5.2 then decreased rapidly 3950±550 λ=7.5 nm. Further increases resulted slower decrease H 3640±550 λ=32 large error bars SLS samples due difficulty measuring such extremely high hardnesses thin films. (H pure single-crystal TiN VN 2200±300 1620±200 mm−2, respectively.) constant λ=6.5 nm, but different /λ ratios, exhibited /λ≂0.3.