Nanoscale geometrical patterning for junctionless thermoelectrics

Classical thermoelectric (TE) phenomena require a junction between two dissimilar materials with different Seebeck coefficients to either generate current via temperature differences at the junctions (Seebeck effect) or to cool/heat these junctions by applying external current (Peltier effect). While modifying the Seebeck coefficient via material composition and heterostructuring using different materials is well known, changing the Seebeck coefficient of a uniform material just by geometrical patterning was neither known, nor foreseen. Here, we report, for the first time, the ability to engineer the Seebeck coefficient, the dominant parameter of TE performance, in an arbitrary large area of a single uniform two-dimensional (2D) material by geometrical patterning. The Seebeck coefficient modification decays in an exponential manner, over a characteristic “decay length”, dTE ~ 1 μm, that we link to the product of Fermi velocity of the charge carriers and the time of phonon-electron energy exchange in a 2D material. By constructing nanopatterns of voids with pitch smaller than dTE, we effectively create TE “junctions”, opening up novel avenues for thermal management in nanoelectronics, photodetector arrays and TE energy generation.