Reactions of thin film bilayers of nickel on silicon-germanium alloys

Solid state reactions between 1000A thick Nickel films and 4000A thick amorphous Si$\sb{\rm 1-x}$Ge$\sb{\rm x}$ films, deposited with the Molecular Beam Epitaxy (MBE) technique, are examined with the novel use of two in-situ analytical techniques: An in-situ 4-point probe resistance measurement, done during vacuum annealing of the bilayers, yields information about changes in the whole electrically conductive volume of the film structure. In-situ X-ray Photoelectron Spectroscopy (XPS) is also done during vacuum annealing of the bilayer structure, and yields information about phase changes that occur at the surface of the sample. The combination of cross-sectional Transmission Electron Microscopy (XTEM) and X-ray Diffraction (XRD) analyses of specifically heat treated samples with the in-situ measurements allows identification of: the first phase to form, the phase formation sequence, the kinetics of phase formation, and the primary diffusing species.In the case of Ni-Si reactions, the final phase formed during annealing below 500$\sp\circ$C is NiSi through a diffusion limited reaction with an effective activation energy E$\sb{\rm a}$ = 1.75 eV. In the case of Ni-Ge reactions, the final phase formed during annealing below 500$\sp\circ$C is NiGe through a diffusion limited reaction with an effective activation energy E$\sb{\rm a}$ = 1.4 eV. In the case of Ni-Si$\sb{\rm 1-x}$Ge$\sb{\rm x}$ reactions (for x = 0.3, 0.7), the final phase formed during annealing below 500$\sp\circ$C is concluded to be the ternary solid solution phase Ni$\sb{50}$(Si$\sb{\rm 1-x}$Ge$\sb{\rm x})\sb{50}$ where x ranges between approximately 0.8 and 0.4 from the 'top' to 'bottom' of the layer respectively. This layer is observed to form through a diffusion limited reaction initially with Ni-Ge like kinetics (E$\sb{\rm a}$ = 1.4 eV), and the final stages of formation have Ni-Si like kinetics (E$\sb{\rm a}$ = 1.8 eV). Nickel was concluded to be the primary diffusing species in all cases.U of I OnlyETDs are only available to UIUC Users without author permissio