期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：50
页码：14272-14276
DOI：10.1073/pnas.1615913113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe miniaturization of electronic components and the excessive heating produced by the increased power densities in these small devices has heightened the need for on-chip cooling solutions. This has prompted a search for materials with large thermoelectric power factor and thermal conductivity that could be integrated in active thermoelectric coolers. Here, we report record thermoelectric power factors achieved in graphene on hexagonal boron nitride devices, corresponding to more than doubling the highest reported room temperature bulk values. In these devices, the smooth and highly efficient gating between electron- and hole-doped sectors, which facilitates switching the polarity of the Seebeck coefficient, extends a distinct advantage for on-chip thermoelectric cooling applications. Based on these results, we propose an integrated graphene-based active on-chip cooler. Fast and controllable cooling at nanoscales requires a combination of highly efficient passive cooling and active cooling. Although passive cooling in graphene-based devices is quite effective due to graphenes extraordinary heat conduction, active cooling has not been considered feasible due to graphenes low thermoelectric power factor. Here, we show that the thermoelectric performance of graphene can be significantly improved by using hexagonal boron nitride (hBN) substrates instead of SiO2. We find the room temperature efficiency of active cooling in the device, as gauged by the power factor times temperature, reaches values as high as 10.35 W*m-1*K-1, corresponding to more than doubling the highest reported room temperature bulk power factors, 5 W*m-1*K-1, in YbAl3, and quadrupling the best 2D power factor, 2.5 W*m-1*K-1, in MoS2. We further show that the Seebeck coefficient provides a direct measure of substrate-induced random potential fluctuations and that their significant reduction for hBN substrates enables fast gate-controlled switching of the Seebeck coefficient polarity for applications in integrated active cooling devices.
