© Effect Of Phase Transitions In Copper-Germanium Thin Film Alloys On Their Electrical Resistivity Tawancy, HM; Aboelfotoh, MO CHAPMAN HALL LTD, JOURNAL OF MATERIALS SCIENCE; pp: ; Vol: 30 King Fahd University of Petroleum & Minerals Summary An investigation was carried out to study the phase transitions in Cu-Ge thin films ( nm in thickness) containing 0, 5, 15, 20, 25, 30, 35, 40, 45 and 50 at% Ge, and the corresponding effects on electrical resistivity. For these films, the phase transitions were found to follow the sequence: alpha-phase (disordered face centred cubic, fcc, solid solution); 5 at% Ge --> zeta-phase (disordered hexagonal close packed, hcp); 15 at% Ge --> zeta-phase + epsilon(1)-phase (ordered orthorhombic, Cu3Ge); 20 at% Ge --> epsilon(1)-phase; 25 at% Ge --> (epsilon(1)-phase + progressively increasing proportions of a disordered Ge-rich solid solution); at% Ge. Germanium was found to have no marked effect on grain size of all films studied excluding grain boundaries as electron scattering centres. Transition of the alpha-phase into the zeta-phase was found to occur in a highly coherent manner, which could be related to the reduced stacking fault energy of Cu by the addition of Ge. Most evidence pointed out that the initial increase in resistivity within the alpha- phase range was related to hcp scattering centres, which could be associated with a localized high concentration of Ge. At 15 at% Ge, the resistivity reached a maximum value of about 50 mu Omega cm associated with the complete transformation of alpha-phase into the zeta-phase. With continued increase in Ge concentration, the resistivity was found to gradually decrease reaching a minimum value of about 10 mu Omega cm at 25 at % Ge, which was correlated with complete transition of the zeta- phase into the ordered epsilon(1)-phase (Cu3Ge). It was shown that the superlattice of Cu3Ge could directly be derived from the disordered zeta-phase by minor atom Copyright: King Fahd University of Petroleum & Minerals;

© rearrangement on the [ ](hcp) plane. Even though, minor proportions of a Ge- rich solid solution containing a small concentration of Cu were formed at Ge concentrations above 25 at %, the minimum resistivity of 10 Omega mu cm was maintained as the Ge concentration was increased to 35 at%. Subsequently, the resistivity was increased reaching about 46 mu Omega cm at 50 at% Ge. References: ABOELFOTOH MO, 1991, J APPL PHYS, V70, P3382 ABOELFOTOH MO, 1991, PHYS REV B, V44, P12742 ABOELFOTOH MO, 1993, APPL PHYS LETT, V63, P1622 ABOELFOTOH MO, 1994, J APPL PHYS, V75, P2441 BARRETT CS, 1966, STRUCTURE METALS, P358 BARRETT CS, 1966, STRUCTURE MTALS, P247 GOLDSTEIN JI, 1986, PRINCIPLES ANAL ELEC, P155 HANSEN M, 1986, BINARY ALLOY PHASE D, P919 HASSAN P, 1978, PHYSICAL METALLURGY, P127 HENSEL JC, 1984, APPL PHYS LETT, V44, P913 HENSEL JC, 1985, PHYS REV LETT, V54, P1840 HOWIE A, 1961, PHILOS MAG, V6, P1215 JOSSANG T, 1966, PHILOS MAG, V13, P657 KOIKE S, 1982, PHILOS MAG B, V45, P261 KRUSINELBAUM L, 1987, IEEE T ELECTRON DEV, V34, P58 KRUSINELBAUM L, 1991, APPL PHYS LETT, V58, P1341 LAIBOWITZ RB, 1982, TREATISE MATER SCI, V24, P285 MAHAJAN S, 1977, METALL T A, V8, P283 MASALSKI TB, 1959, ACTA METALL, V7, P762 MASSALSKI TB, 1983, PHYSICAL METALLURG 1, P153 SUZUKI T, 1976, J PHYS F MET PHYS, V6, P779 SWANN P, 1961, J I MET, V90, P133 SWANN PR, 1963, ELECT MICROSCOPY STR, P131 VILLARS P, 1985, PEARSONS HDB CRYSTAL, V2, P1948 For pre-prints please write to: Copyright: King Fahd University of Petroleum & Minerals;