Nanocalorimetry: Measuring heat capacity and phase transition in nanoscale samples
During last 20 years GTNAM-UAB group has devoted a significant effort towards the development of more sensitive calorimeters capable to efficiently measure small samples. Calorimetry is a suitable technique to characterize kinetic and thermodynamic properties of materials by measuring the heat released or absorbed by a material during any process. When the aim is to measure ultra-thin films or nanoscopic samples, the calorimetric measurements are troublesome , since the amount of energy released by a given reaction uses to be too small to be measured and analyzed with accuracy using conventional calorimeters (typically limited to samples of few miligrams). The fundamental problem on measuring small samples is related to the ratio between the heat capacity of the calorimetric cell and the heat capacity of the sample, since the calorimetric signal is proportional to the total addenda of the total calorimetric cell, but the transformation signal is only proportional to the sample.
The development of micromachining techniques associated to the Silicon technology has paved the scaling down of the calorimetric cells permitted to envisage a new family of calorimeters, that using the thin suspended membranes as substrate or sample support overcomes the heat capacity addenda problem. In this seminar, we will review the different methods implemented in nanocalorimetry, showing examples, and how the measurement limits have been pushed by the drastic increase in sensitivity.