Time-dependent simulations of a membrane-based nanocalorimeter

Abstract

We present time-dependent numerical simulations of the thermal and electrical response of a membrane-based nanocalorimeter designed for general studies of heat capacity and latent heat of milligram to sub-microgram samples. The investigated device is based on freestanding, 150 nm thick silicon nitride membranes onto which thin film heaters and temperature sensors are fabricated. This design makes the thermal link small enough to allow both relaxation and ac steady-state methods to be used interchangeably. We compare simulations of the two-dimensional thermal behavior of the nanocalorimeter with the results of experiments. The simulations take current distribution, heat generation and heat flow into consideration, and shed light on the frequency dependent contribution of the membrane heat capacity in ac steady-state experiments. The simulations also illustrate where energy is stored, thus assisting further improvement of the device design.