Langenberg Eric, Saha Dipanjan, Holtz Megan E, Wang Jian-Jun, Bugallo David, Ferreiro-Vila Elias, Paik Hanjong, Hanke Isabelle, Ganschow Steffen, Muller David A, Chen Long-Qing, Catalan Gustau, Domingo Neus, Malen Jonathan, Schlom Darrell G, Rivadulla Francisco
Department of Materials Science and Engineering , Cornell University , Ithaca , New York 14853 , United States.
Centro Singular de Investigación en Quı́mica Biolıoxica e Materiais Moleculares (CiQUS), Departmento de Quı́mica-Fı́sica , Universidade de Santiago de Compostela , Santiago de Compostela 15782 , Spain.
Nano Lett. 2019 Nov 13;19(11):7901-7907. doi: 10.1021/acs.nanolett.9b02991. Epub 2019 Oct 14.
Achieving efficient spatial modulation of phonon transmission is an essential step on the path to phononic circuits using "phonon currents". With their intrinsic and reconfigurable interfaces, domain walls (DWs), ferroelectrics are alluring candidates to be harnessed as dynamic heat modulators. This paper reports the thermal conductivity of single-crystal PbTiO thin films over a wide variety of epitaxial-strain-engineered ferroelectric domain configurations. The phonon transport is proved to be strongly affected by the density and type of DWs, achieving a 61% reduction of the room-temperature thermal conductivity compared to the single-domain scenario. The thermal resistance across the ferroelectric DWs is obtained, revealing a very high value (≈5.0 × 10 K m W), comparable to grain boundaries in oxides, explaining the strong modulation of the thermal conductivity in PbTiO. This low thermal conductance of the DWs is ascribed to the structural mismatch and polarization gradient found between the different types of domains in the PbTiO films, resulting in a structural inhomogeneity that extends several unit cells around the DWs. These findings demonstrate the potential of ferroelectric DWs as efficient regulators of heat flow in one single material, overcoming the complexity of multilayers systems and the uncontrolled distribution of grain boundaries, paving the way for applications in phononics.
实现声子传输的高效空间调制是通往使用“声子电流”的声子电路道路上的关键一步。凭借其固有的可重构界面，畴壁（DWs），铁电体是极具吸引力的候选材料，可被用作动态热调制器。本文报道了在各种外延应变工程铁电畴配置下，单晶PbTiO薄膜的热导率。结果表明，声子传输受到畴壁密度和类型的强烈影响，与单畴情况相比，室温热导率降低了61%。获得了铁电畴壁的热阻，其值非常高（≈5.0×10 K m W），与氧化物中的晶界相当，这解释了PbTiO中热导率的强烈调制。畴壁的这种低热导率归因于PbTiO薄膜中不同类型畴之间的结构失配和极化梯度，导致畴壁周围几个晶胞范围内的结构不均匀性。这些发现证明了铁电畴壁作为单一材料中热流高效调节器的潜力，克服了多层系统的复杂性和晶界的无控制分布，为声子学应用铺平了道路。
