MEASUREMENTS OF THERMAL TRANSPORT IN LOW-STRESS SILICON-NITRIDE FILMS

We have measured the thermal conductance, G, of approximate to 1 mu m thick low stress silicon nitride membranes over the temperature range, 0.06<T<6 K, as a function of surface condition. For T>4 K, G is indep endent of surface condition indicating that the thermal transport is d etermined by bulk scattering. For T<4 K, scattering from membrane surf aces becomes significant. Membranes which have submicron sized Ag part icles glued to the surface or are micromachined into narrow strips hav e a G that is reduced by a factor as large as 5 compared with that-of clean, solid membranes with the same ratio of cross section to length. (C) 1998 American Institute of Physics.