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Mat. Res. Soc. Symp. Proc. Vol. 623 © 2000 Materials Research Society

FTIR spectra Pvresented here will show that a pair of weakly intense absorption bands at 1470 and 1395cm is present in CuAlxOy films that have enhanced electrical conductivity and IR transparency. The fact that the frequencies of the 1470 and 1395cm-' bands are about twice those of the major phonons in Cu 20 and A120 3 is significant and indicates that this pair of bands may involve cumulated Cu--0-O Al----0-=-Cu bonds along the c-axis. Higher-order bonding tends to enhance carrier mobility. Furthermore, higher-order bonding in a metal oxide would likely result from an oxygen deficiency. Understanding the origin of these bands could speed development of magnetron-sputter-deposited CuAlxOy as a wide-bandgap-conductive oxide since these bands are clearly associated with enhanced conductivity and carrier mobility. The delafossite structure of CuA10 2 to some degree mimics the structures of high-temperature-superconducting-copperoxide compounds on an atomic scale. The pair of bands at 1470 and 1395cm' may be associated with the phonon-assisted electrical conduction and Cooper-pair phenomena that are used to explain superconductivity [3]. Hall-effect measurements also show that our CuAlOy films are ptype so lattice vibrations probably are involved in the enhanced conductivity. Cumulated Cu-OA-k"---AI--"O=Cu bonds would requirepz orbitals on 0 to overlap with pz orbitals on Al and d Z orbitals on Cu atoms. Using a new technique that combines conventional XRD with electron-beam diffraction, Zuo et al. were able to observe directly the classic textbook shape of a d 2 orbital in p-type Cu 20 [4]. The work by Zuo et al. is expected to be a first step toward understanding high-temperature-superconducting-copper-oxide compounds and may help explain the enhanced conductivity and IR transparency in our sputter-deposited CuA1IOy films. EXPERIMENTAL APPROACH An automated-research-coating (ARC) system equipped with three magnetron guns is used to deposit CuAlxOy by co-sputtering from high-purity-Al and -Cu targets in a reactive-Ar-0 2 mixture. The purity of each of the 2-in-diam-metal targets is at least 0.99999. The ARC system is equipped with two 600W-rf-power supplies and one 250W-dc-power supply. The watercooled chamber is a 12-in-diam by 14-in-high stainless-steel cylinder and is configured for downward sputtering onto a rotating substrate table with a target-substrate distance of about 5.5in. By rotating the substrate underneath the guns, it is possible to obtain good film uniformity over an 8-in-diam wafer. For the CuAlOy films, the rotation speed of the substrate table was set to 10rpm. The vacuum system consists of a 250-liter-per-sec turbomolecular pump from Varian and a direct-drive oil-filled rough pump Trivac model D8B from Leybold. As the chamber is back-filled, the turbopump automatically slows down to half-speed to minimize the gas load and prevent excessive wear on the bearings. For these experiments, the 02-partial pressure ranged from 0.7% to 1