ION-ASSISTED GROWTH OF TI1-XALXN TI1-YNBYN MULTILAYERS BY COMBINED CATHODIC-ARC/MAGNETRON-SPUTTER DEPOSITION/

The microstructure and microchemistry of polycrystalline Ti1-x-yAlxNby N alloys and Ti1-xAlxN/Ti1-yNbyN multilayers grown on bcc ferritic sta inless steel substrates at 450 degrees C by unbalanced-magnetron (UBM) sputter deposition and combined UBM/cathodic-arc (UBM/CA) deposition have been investigated using X-ray diffraction, scanning electron micr oscopy, Rutherford backscattering spectrometry, cross-sectional transm ission electron microscopy (XTEM), and scanning transmission electron microscopy with energy-dispersive X-ray microanalyses of XTEM samples. The growth experiments were conducted in a deposition system in which the substrates are continuously rotated past one Ti0.85Nb0.15 and thr ee Ti0.50Al0.50 cathodes, each capable of being operated independently in either UBM or CA mode. CA ion-etching of the steel substrates prio r to deposition produced a polycrystalline compositionally-graded alte red layer with a depth of similar or equal to 20 nm when operating the are on the Ti0.50Al0.50 target and a much narrower, similar or equal to 6 nm, amorphous layer with the Ti0.85Nb0.15 target. Subsequent UBM or UBM/CA growth on substrates subjected to the former treatment resul ted in local epitaxy with underlying grains for film thicknesses up to similar or equal to 200 nm before the growth front gradually broke do wn locally to initiate columnar deposition. Film growth on substrates CA ion-etched using the Ti0.85Nb0.15 target resulted in much smaller a verage column diameters with competitive grain growth. However, the fr action of the sample area covered by nodular defects arising from are- ejected droplets was reduced by a factor of similar or equal to 102. T hus the latter procedure was used for substrate preparation prior to m ultilayer growth. Ti1-xAlxN/Ti1-yNbyN multilayers with periods between 2.17 and 2.29 nm were grown by combined UBM/CA deposition. The multil ayers exhibited flat, regular interfaces throughout film total thickne sses of up to 3 mu m. (C) 1997 Elsevier Science S.A.