PHYSICAL-DEPENDENCE OF THE SENSITIVITY AND ROOM-TEMPERATURE STABILITYOF AUXGE1-X THIN-FILM RESISTIVE THERMOMETERS ON ANNEALING CONDITIONS

The reported nearly constant temperature sensitivity of appropriately annealed polycrystalline AuxGe1-x thin films at cryogenic temperatures would appear to make them promising materials for low mass, rapid the rmal response resistive thermometers, but their adoption has been limi ted by difficulties in fabrication and uncertainties in annealing. In this work, we present a method of fabrication and annealing which allo ws control of the two most important parameters for these films: the r oom-temperature resistivity rho(RT) and the temperature sensitivity et a(T), where eta = -d In R/d In T. We find that the dependence of rho(R T) On total anneal duration r for x approximate to 0.18 is given by rh o(RT) = rho(infinity)[1-Aexp(-t/tau)], where the limiting room-tempera ture resistivity rho(infinity), the annealing coefficient A, and relax ation time tau are annealing temperature dependent parameters. The dep endence of rho(RT) and temperature calibration rho(T) on anneal durati on can be minimized by annealing above 250 degrees C. Like rho(RT), th e sensitivity eta(T) also depends on annealing temperature, with highe r annealing temperatures corresponding to lower cryogenic sensitivitie s. In all cases eta(T)(T) can be well described by a polynomial expans ion in In T from room temperature down to at least 2 K. (C) 1998 Ameri can Institute of Physics.