[18p-E214-1~13] 22.1 Joint Session M "Phonon Engineering"

▼ [18p-E214-12] Anisotropic Heat Transport of Natural Superlattice Oxide, InGaO₃(ZnO)_m

〇(M2)Yuzhang Wu¹, Hai Jun Cho^1,2, Bin Feng³, Masashi Mikami⁴, Woo Seok Shin⁴, Yuichi Ikuhara³, Keiji Saito⁵, Hiromichi Ohta^1,2 (1.IST-Hokkaido Univ., 2.RIES-Hokkaido Univ., 3.Tokyo Univ., 4.AIST, 5.Keio Univ.)

Keywords:Phonon transport, Thermal conductivity, Superlattice

Clarification of anisotropic heat transport behaviour in two dimensional superlattice is significantly important for developing heat modulation devices like thermal diodes. Here we report an epoch-making method to measure the thermal conductivity anisotropy of InGaO₃(ZnO)_m (m = integer), which has a natural superlattice structure with adjustable periods. We fabricated single crystalline InGaO₃(ZnO)_m thin films by the reactive solid-phase epitaxy on YSZ single crystal substrate and modulated the periods of the superlattices from 0.9 to 11.3 nm. The inclined angle of the c-axis is 0° for (111) YSZ and 15° for (110) YSZ. Out-of-plane thermal conductivity (κ) of both horizontal and inclined InGaO₃(ZnO)_m were measured by the TDTR method at room temperature. Unlike normal superlattices, which exhibits a minimum as a function of interface density, the inclined superlattices shows a monotonic TDTR response pattern, which shows that the phonons in the in-plane direction are significantly affected by phonon band folding. In this study, we clarified the effect of interface density on in-plane κ of InGaO₃(ZnO)_m, which can help development of two-dimensional thermal materials.