Specific heat of thin-film amorphous molybdenum-based alloys

We have studied the effects of transition-metal (TM) and metalloid (M) substitution in amorphous molybdenum-based TM-M alloys. Absolute-specific-heat measurements of thin-film (∼1 μm thick) samples of Mo-Ge, Mo-Si, and Mo-Ti-Si alloys prepared by magnetron sputtering were made using the relaxation-time-constant method. A comparison of the superconducting transition width made both thermally and electrically indicates that the sample homogeneity is better than 0.1% for length scales greater than the coherence length. Both the electronic density of states and $T_c$ with increasing metalloid concentration and [Ti]/[Mo] ratio, in agreement with a rigid-band model. We compare our results to current theories relating the electron-phonon coupling constant ${\lambda }_{e\mathrm{-}\mathrm{ph}}$ to the electronic density of states.