Figure 4

Text Box: Fig. 4. The electron cooling time te-ph(T) for 250 Å-thick Hf films with resistivity r = 0.1 mW×cm. For the other three Hf films with similar r, te-ph was in the range 4 – 9 ms at T = 40 mK. The solid line is the dependence te-ph(T) (Eq. 2) calculated for Hf with r = 0.1 mW×cm.