Graded Al-AlN, TiN, and TiAlN multilayers deposited by radio-frequency reactive magnetron sputtering

Graded layers and multilayers have been reported to improve surface propert ies of steel tools. Our study was aimed at defining the appropriate process ing parameters for deposition of graded AI-AIN and AlN-TiN-TiAlN multilayer s on silicon, glass, and M2 steel tools. The layers were deposited by r.f r eactive magnetron sputtering using dual cathode targets, Ti and Al. The rat io of nitrogen flow to nitrogen plus argon flow (f(N2)/f((N2+Ar))), r.f. po wer, and bias voltage (V-B) were used as the processing parameters. These p arameters may be varied continuously, thus allowing the formation of a grad ed structure. The layers were characterized with regard to structure, compo sition, and mechanical properties using Fourier transform IR (FTIR) spectro meter, X-ray diffractometry, Auger electron spectroscopy microscope, Vicker s microhardness tester, and scratch tester (testing adhesion). The reactive sputtered AlN layers displayed oriented (10 (1) over bar 1) or (0002) crys talline structure dependent on the gas pressure, while the graded Al-AlN la yer had an oriented (0002) AlN structure and a randomly oriented Al structu re with (0002) the highest peak. FTIR spectra of ALN thick layers showed sh arp and intense absorbance bands at 1025 cm(-1), 930 cm(-1), and 544 cm(-1) . However, peaks related to thin films were seen to be broadened and shifte d compared with those of thick films. The TiN and TiAlN layers displayed (1 11) oriented crystalline structures of delta-TiN and high microhardness and adhesion characteristics. The relationship between the processing paramete rs and the structure of the layers formed is presented and discussed. (C) 1 999 Elsevier Science S.A. All rights reserved.