Double–layered GeTe/Sb2Te heterostructures for enhancing thermoelectric performance

Abstract

This work reports the preparation and properties of double–layered GeTe/Sb2Te heterostructures that exhibit remarkable improvement in thermoelectric performance compared to single layer systems. The double–layered (GeTe)80 nm/(Sb2Te)100 nm achieved a maximum power factor value of 413 μW/mK2 at 500 K. Notably, by tuning layer thickness ratios, the reduction of transition temperatures and lowering in the resistance drift can be also achieved. Thermal heating of the amorphous heterostructures reveals intermixing between the layers, which results in the formation of GeSb2Te4 as the first phase and the crystallization of GeTe layer at higher temperatures. The crystallization process led to the increase in electrical conductivity of the heterostructures. Moreover, the newly formed GeSb2Te4/GeTe interfaces induce the strong energy barrier to block carriers, thus contributing to the increased Seebeck coefficient and power factor. Overall, this work shows a way to improve materials properties by using double–layered chalcogenide heterostructures.