Heat capacity per unit volume

In the thermal design of micro-electro-mechanical systems, micro-electronics, etc., it is necessary to solve thermal conduction equation at various boundary conditions. In such an analysis the values of thermophysical properties in a thin film on a substrate, a superlattice, an interfacial region, etc. which have usually width with a nanometer scale are required. Among the thermophysical properties, heat capacity per unit volume in a small-scale region is difficult to measure and then, we need to estimate it in an appropriate way. In this paper, I propose that the heat capacity per unit volume at room temperature lies around 2 × 106 J m−3 K−1 over a variety of materials, contrary to the thermal conductivity which markedly depends on a material and the state of a material, especially whether it is ordered or disordered. Then, we can use the above heat capacity per unit volume for a small-scale region in a practical purpose.