Potential & Seebeck Microprobe – Imaging of electrical and thermoelectric material properties on the microscale

Recent developments turned the Potential & Seebeck Microprobe (PSM) into a powerful tool for electrical functional materials characterisation. A wide spectrum of applications has been demonstrated including thermoelectric cobalt antimonide and bismuth telluride films including nano-structured thick films. The principle involves a heated probe tip positioned at the surface of a sample coupled to a heat sink. The probe tip contains a thermocouple, the sample is connected to another thermo¬couple, together forming independent circuits containing the probe–sample contact. The sample is scanned by mechanically touching and again disconnecting the surface at each position. A rapidly sensing electronic contact detection prevents fragile thin films down to 1 µm and thinner from being damaged by the probe tip. The tip is heating up the sample in a micro-vicinity, forming a locally focused temperature gradient. By several measuring circuits, thermo-voltages and the temperature drop over the gradient region are recorded, yielding the local Seebeck coefficient. With an electrical current fed through, the potential profile over the sample is monitored. Micro-resolving images both of the Seebeck coefficient and the potential obtained in a single run provide information on functional effects of the distribution of chemical compo¬nents, phases, alloying elements, or dopants. The method is particularly helpful to study functionally segmented or graded materials. The facility is suitable for low resistivity materials which are difficult because of extremely low signals