Reactions between a Ge substrate and a sputter deposited Ti film

Formations of germanides in thin films of the Ti-Ge system were investigated by XRD after rapid thermal annealing (RTA) at several temperatures for various times. Phase formation depends on the conditions of the experiments and specifically on the thickness of the Ti film relative to that of the Ge. Considering the equilibrium phase diagram of the Ti-Ge system, if the composition is close the Ge rich side, TiGe2 might be expected to be the first phase to form and the phases present would be TiGe2 and Ge. However this is not the case. If the composition of the constituents is between the compounds of Ti6Ge5 and TiGe2, the first formation can be either one of these, but depends on how close it is to any of these compounds. However Ti6Ge5 is observed always to be the first phase. The presence of Ti6Ge5 and Ti5Ge3 is observed when the composition shifts to a location between these compounds on the phase diagram. Coexistence of Ti and Ti5Ge3 is a possibility when the amount of Ge is below the concentration of the phase Ti5Ge3, namely, when the Ge constituent is completely consumed and excess of Ti is left behind after the reaction. Temperature and time are major parameters that determine the outcome of the reactions between Ti and Ge during RTA and any of these can override the influence of the composition. XRD, SEM, Auger, TEM and resistivity were the experimental tools to study the Ti-Ge system and to evaluate the phases present under a set of experimental conditions.