Investigation of a Microcalorimeter for Thin-Film Heat Capacity Measurement

A microcalorimeter is studied for testing heat capacity of thin films. The microcalorimeter is a suspended membrane supported by six microbridges, which is fabricated by the front-side surface micromachining. Compared to the bulk micro-machined one, the microcalorimeter has excellent mechanical strength and precisely controlled pattern size as well as good thermal characteristics that are essential to a microcalorimeter. The heating rate of the microcalorimeter is up to 2 × 10^5Kis with 4.5mW heating power in vacuum, and the heat capacity of the corresponding empty microcalorimeter is about 23.4nJ/K at 30OK. By a pulse calorimetry, the heat capacity of A1 thin films with thickness of 40-1150nm are measured in the temperature range from 300K to 420K in vacuum. The mass of each sample is evaluated and the specific heat capacity is calculated. The results show that specific heat capacity of the 1150-nm A1 film agrees well with the data of bulk A1 reported in the literature. For the thinner films, enhanced heat capacity is observed.