Measuring thermoelectric property of nano-heterostructure

A method of measuring the thermoelectric power of nano-heterostructures based on four-probe scanning tunneling microscopy is presented. The process is composed of the in-situ fabrication of a tungsten-indium tip, the precise control of the tip-sample contact and the identification of thermoelectric potential. When the temperature of the substrate is elevated, while that of the tip is kept at room temperature, a thermoelectric potential occurs and can be detected by a current-voltage measurement. As an example of its application, the method is demonstrated to be effective to measure the thermoelectric power in several systems. A Seebeck coefficient of tens of mu V/K is obtained in graphene epitaxially grown on Ru (0001) substrate and the thermoelectric potential polarity of this system is found to be the reverse of that of bare Ru (0001) substrate.