INTERFACESCIENCE 1, 61-75 (1993). 9 KluwerAcademic Publishers,Boston. Manufactured in The Netherlands. The Chemical Composition of a Metal/Ceramic Interface on an Atomic Scale: The Cu/MgO {111} Interface H. JANG AND D.N. SEIDMAN Northwestern University, Department of Materials Science and Engineering and the Materials Research Center, Robert R. McCormick School of Engineering and Applied Science, Evanston, IL 60208 K.L. MERKLE Argonne National Laboratory, Materials Science Division, Building 212, Argonne, IL 60439 Received September 28, 1992; Revised November 30, 1992. Keywords: Metal/ceramic interface, internal oxidation, Cu/MgO heterophase interface, high resolution electron microscopy, atom-probe field-ion microscopy. Abstract. The chemical composition profile across a Cu/MgO {lll}-type heterophase interface, produced by the internal oxidation of a Cu(Mg) single-phase alloy at 1173 K, is measured via atom- probe field-ion microscopy with a spatial resolution of 0.121 nm; this resolution is equal to the interplanar spacing of the {222) MgO planes. In particular, we demonstrate directly that the bonding across a Cu/MgO {lll}-type heterophase interface, along a <111> direction common to both the Cu matrix and an MgO precipitate, has the sequence CulOIMg... and not CulMglO... ; this result is achieved without any deconvolution of the experimental data. Before determining this chemical sequence, it was established, via high-resolution electron microscopy, that the morphology of an MgO precipitate in a Cu matrix is an octahedron faceted on {111} planes with a cube-on-cube relationship between a precipitate and the matrix; that is, {111}Cu//{222}MgO and < 110 >cu//< 110 >MgO. 1. Introduction Metal/ceramic heterophase interfaces are cur- rently receiving a great deal of experimental attention because they are omnipresent in a wide range of materials and structures [1-6]; for example, metal matrix composites with ce- ramic fibers [7], metal/ceramic nanocomposites [8], machinable ceramics, metallization of mi- croelectronics circuit structures [9], semiconduc- tor devices, oxide scales on metals [10], and dispersion-hardened alloys [11]. The cohesive energies of metal/ceramic interfaces have also been the focus of much theoretical effort, as ultimately the behavior of a metal/ceramic het- erophase interface in service is determined by how well these rather disparate materials adhere to one another [12-14]. In particular, on the ex- perimental side, a great deal of energy has been expended employing high-resolution electron mi- croscopy (HREM) to determine the terminating plane on the oxide side of metal/metal oxide het- erophase interfaces by comparing HREM micro- graphs with micrographs computed using image- simulation techniques [15-17]. In this paper we present the results of a dif- ferent approach for studying the chemical char- acter of metal/ceramic heterophase interfaces. We employ atom-probe field-ion microscopy (APFIM) to ascertain directly-on an atomic scale-the chemical compositions of individual atomic planes in traversing Cu/MgO {lll}-type