Hard nanocrystalline Zr–B–C–N films with high electrical conductivity prepared by pulsed magnetron sputtering

Abstract

Zr–B–C–N films were deposited on silicon and glass substrates using pulsed magnetron co-sputtering of a single B4C–Zr target (at 15% or 45% of zirconium in the target erosion area) in nitrogen–argon gas mixtures. A planar unbalanced magnetron was driven by a pulsed dc power supply operating at a repetition frequency of 10kHz with a fixed 85% duty cycle. The total pressure was 0.5Pa and the substrate temperature was adjusted to 450°C during the depositions on the substrates at a floating potential. High-quality defect-free films, 3.5 to 4.1μm thick, with smooth surfaces (the average roughness Ra≤4nm) and good adhesion to substrates at low compressive stresses (less than 0.9GPa) were produced. Hard (37GPa) nanocolumnar ZrB2-type films of the Zr25B57C14N3 composition (in at.% without 1at.% of hydrogen) with a very low compressive stress (0.4GPa), high electrical conductivity (electrical resistivity of 2.3×10−6Ωm) and high oxidation resistance in air up to 650°C were prepared in pure argon at a 15% Zr fraction in the target erosion area. Hard (37GPa) nanocomposite Zr41B30C8N20 films with a low compressive stress (0.6GPa), even higher electrical conductivity (electrical resistivity of 1.7×10−6Ωm) and high oxidation resistance in air up to 550°C were deposited in a 5% N2+95% Ar gas mixture at a 45% Zr fraction in the target erosion area. Increasing the N2 fraction (>5%) in the gas mixture resulted in a significant decrease of the film hardness and in a rapid rise in their electrical resistivity and oxidation resistance in air at elevated temperatures due to a growing volume fraction of an amorphous phase with a high content of nitrogen (up to 52at.%) in the materials.