Specific heat of amorphous silicon at low temperatures

The heat capacity of amorphous silicon has been measured between 2 and 50 K using an a.c. calorimetry technique. A comparison with heat capacity measurements of crystalline silicon shows a reduction of the Debye temperature by a factor 0.82 and of the position of the maximum in $\text{c}\text{T}{}^3$ by a factor of 0.77. This behaviour indicates a general reduction in frequency of the transversal-acoustic modes with respect to the corresponding modes of crystalline silicon.