Monitoring microstructure and phase transitions in thin films by high-temperature resistivity measurements

We present first experimental results obtained with a newly patented high-temperature resistivity measurement apparatus. This technique is of great interest for monitoring the behaviour of a surface layer submitted to high temperature, either during its processing or while the functional surface is used. The innovation resides in the combination of features that are available commercially or have previously been reported by research groups worldwide, but isolated. Resistivity measurements can be performed under vacuumor controlled atmosphere, fromroomtemperature to 1250°C, on samples as low as 10*10mm2 in size. Technical details about the apparatus are presented. Then, we show that high-temperature resistivity measurements performed on a platinum sheet compare well with available data, and validate the prototype measurement head. Finally, we explore the monitoring of phase transitions occurring in an Al/Cu bilayer processed by metallorganic chemical vapour deposition, while a temperature ramp is applied. The high-temperature resistivity plot is very well explained by the following sequence of phase formation: Al + Cu!θ-Al2Cu+ Cu+ Al!d-Al2Cu3 + g-Al4Cu9+Cu!d-Al2Cu3 + g-Al4Cu9+Cu+a-(Cu), as determined by hightemperature X-ray diffraction.