Thin film nanocalorimeter for heat capacity measurements of 30 nm films

A silicon nitride membrane-based nanocalorimeter is described for measuring the heat capacity of 30 nm films from 300 mK to 800 K and in high magnetic fields with absolute accuracy similar to 2%. The addenda heat capacity of the nanocalorimeter is less than 2x10(-7) J/K at room temperature and 2x10(-10) J/K at 2.3 K. This is more than ten times smaller than any existing calorimeter suitable for measuring thin films over this wide temperature range. The heat capacities of thin Cu and Au films are reported and agree with bulk values. The thermal conductivity of the thin low stress silicon nitride is substantially smaller than thicker membranes while the specific heat is enhanced below 20 K. Design of the nanocalorimeter will be discussed along with fabrication details and calibration results.