HIGH-SPEED (10(4)-DEGREES-C S) SCANNING MICROCALORIMETRY WITH MONOLAYER SENSITIVITY (J/M(2))/

We introduce a high sensitivity (1J/m(2)) scanning microcalorimeter th at can be used at high heating rates (10(4) degrees C/s). The system i s designed using ultrathin SiN membranes that serve as a low thermal m ass mechanical support structure for the calorimeter. Calorimetry meas urements of the system are accomplished via resistive heating techniqu es applied to a thin film Ni heating element that also serves as a the rmometer. A current pulse through the Ni heater generates heat in the sample via Joule heating. The voltage and current characteristics of t he heater were measured to obtain real-time values of the temperature and the heat delivered to the system. This technique shows potential f or measuring irreversible heat of reactions for processes at interface s and surfaces. The method is demonstrated by measuring the heat of fu sion for various amounts of thermally evaporated Sn ranging from 50 to 1000 Angstrom. (C) 1995 American Institute of Physics.