Adhesion of Metals to Mixed Oxide Coatings (Al & Cr, Mo, OR W) Prepared by Spray Pyrolysis of Organometallics.
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ADHESION OF METALS TO MIXED OXIDE COATINGS (Al & Cr, Mo, OR W) PREPARED BY SPRAY PYROLYSIS OF ORGANOMETALLICS.
JAMES M. BURLITCH*, GERARD J. DeMOTr**, AND DAVID L. KOHLSTEDT** * Dept. of Chemistry, Cornell University, Ithaca, NY 14853-1301. "**Dept.of Materials Science & Engineering, Cornell University, Ithaca, NY 14853.
ABSTRACT Spray pyrolysis of the mixed metal organometallics, AI[M(CO) 3 C5 H5 ]3 (M is Cr, Mo or W), prepared in tetrahydrofuran from the mercury analogues and aluminum metal, gave mixed oxide gels on heated alumina substrates. Air was used as the propellant for M = Cr, whereas oxygen was used for M = Mo or W. Mixtures of AI[Cr(CO) 3 C5 H5 ]3 and AI(O-i-C 3 H 8 )3 having a Cr/Al ratio of 0.02 to 0.93 were used to prepare gels with intermediate dopant concentrations. When calcined at 500 °C, the gels produced amorphous coatings of two-component oxides that were characterized by SEM and EDS methods. The strength of adhesion of a E-beam evaporated chromium metal overlayer to the coating, as measured by a continuous microindentation method, increased in the order Cr < Mo =- W; adhesion was found to be directly proportional to the effective free energy of formation of the oxide mixture. INTRODUCTION Control of the strength of a metal/ceramic interface is important in many recent technological developments. For example, the use of ceramic substrates for integrated circuits [1] requires a metal conductor film bonded directly to the ceramic. Two mechanisms have been proposed to describe the bonding of metals to oxides. A 'chemical' interaction may occur when the metal-to-ceramic interface consists of a continuous, thin layer of an oxide of the metal[2]. Alternatively, a mechanical 'interlocking' of the metal and the oxide may be responsible for bonding[3]. Chromium metal has been employed as an intermediate layer between copper thin films and aluminmt oxide substrates. Recent studies of the strength of adhesion of chromium to gel-derived oxide coatings by means of pull tests [4] and by a continuous microindentation method [5] have suggested that both of these mechanisms may be operative. The amount and type of a dopant metal which could be introduced into the coatings was limited by segregation in the gel process. To learn more about the factors which may affect the adhesion of chromium to metal oxides and, in particular, to learn what might be done to improve the strength of the bond between these two dissimilar materials, we prepared a series of amorphous, oxide coatings on alumina substrates, in which a Group VI metal was introduced by means of the mixed metal complex, AI[M(CO) 3 C5 H 5 ]3 (M is Cr, Mo or W) [6], and we measured the chromium metal-to-oxide interface bond strength by the microindentation method[7]. Mat. Res. Soc. Symp. Proc. Vol. 131. q1989 Materials Research Society
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EXPERIMENTAL Preparation of Coatings Tetrahydrofuran (dry, distilled from potassium benzophenone) solutions of the complexes AI[M(CO) 3 C5 H 5 ]3 (M is Cr, Mo or W) were prepared from the analogous mercury derivativ
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