Thermal memory cell and thermal system evaluation

A method for determining the thermal history of an object is disclosed. The object carries at least two thermal calibration materials having different activation energies. The method comprises: first, exposing an object to a thermal treatment; second, detecting the change in each of the calibration materials caused by the thermal treatment; and third, determining the thermal history of the thermal treatment from the detected changes. Also disclosed are thermal history recording devices comprising one or more metal insulator semiconductor (MIS) capacitors (10). The insulating layer (12) is non-uniformly doped with mobile charged carriers (15). Two or more MIS capacitors (10), each having different activation energies, may be mounted in a common support structure to provide a thermal memory cell. The thermal cells may be used in conjunction with an apparatus for determining the thermal history of the cells as also disclosed herein.