Development of microdevices for the in-plane thermoelectric characterization of deposited films

Measuring the thermoelectric transport properties of a material is a prerequisite to determining its usefulness for application in waste heat recovery or cooling and the basis for devising improvement strategies. While well-established characterization methods exist for bulk samples, characterization of microscale samples remains challenging. This usually results in incomplete characterization such as restriction to study of the thermal transport properties, which can be misleading. While elaborate microdevices for complete thermoelectric characterization have been fabricated, a demanding transfer of the samples onto these devices is generally required and establishing sufficient electrical contact can be challenging in this case. Therefore a complete and transfer free in-plane characterization method for samples obtained by deposition processes was developed. The approach is based on expanding a well-established self-heating technique for the measurement of electrical and thermal conductivity to allow, in addition, for the measurement of the Seebeck coefficient. The fabrication exclusively involves photolithography and wet etching, with no need for other steps like electron-beam lithography and a lift-off process. The accuracy of the method is verified by numerical studies closely mimicking the actual measurement process, comparison to measurements on simultaneously deposited reference samples and results from literature.