原子層沉積金屬氧化物熱電性質研究：不同氧化物插層對鉿摻雜氧化鋅薄膜之影響

Abstract

優秀的熱電性能需同時擁有高電導率、高賽貝克係數以及低熱導率，但三種因子彼此的抗衡是熱電領域中最大的阻礙，其中能量過濾效應被視為能打破電導率與賽貝克係數之間抗衡的方法之一。本研究利用原子層沉積技術，製備以鉿摻雜氧化鋅作為母材，在其中週期性的插入多種金屬氧化物插層的超晶格結構之熱電薄膜。利用異質介面降低母材熱導率的同時，透過不同能階匹配之插層，以達到最佳的能量過濾效應與熱電性質之提升。 研究發現，在母材中插入高原子量的純二氧化鉿插層，雖在抑制熱導率方面有優異的表現，但其高能障卻阻擋了過多的電子以致不佳的電導與ZT。而插入能障較二氧化鉿低的純二氧化鈦或純二氧化鋯插層，能使更多的電子通過而提升電導率，但其低原子量使抑制熱導率的效果不佳，限制了ZT之提升。因此，我們在母材中插入二氧化鈦和二氧化鉿之混合插層，使其達到適當的能障高度，卻仍保有二氧化鉿的高原子量以抑制熱導率，最終使ZT相較只插層雜純氧化鉿的效率高了將近四十二個百分比之多。結果表明，選擇適當的能障高度與高原子量之插層，能透過能量過濾效應保持高PF的同時，大幅降低熱導率並有效地改善熱電效率。

High thermoelectric performances require high electrical conductivity (), high Seebeck coefficient (S) and low thermal conductivity (), but simultaneously achieving the three requisite properties is challenging due to the trade-off relations among them. This study utilized atomic layer deposition (ALD) to prepare superlattice films composed of a conductive Hf:ZnO matrix periodically inserted with interlayers of TiO2, ZrO2, HfO2, or mixtures of the three, leveraging the energy-filtering and phonon-scattering effects of the interlayers to enhance  and S while lowering . The pure HfO2 interlayer were the most effective in suppressing k due to the high atomic mass of Hf, and its high energy barrier with the Hf:ZnO matrix significantly enhanced S through energy filtering, but it also caused a large decline in , limiting the attainable thermoelectric figure of merit, ZT. Conversely, the pure TiO2 and ZrO2 interlayers, with their lower energy barriers and the lower atomic mass of Ti and Zr, yielded higher , lower S, and higher , resulting in ZT values that were only marginally higher than that with the HfO2 interlayer. Combining the low-energy-barrier/low-atomic-mass TiO2 and the high-energy-barrier/high-atomic-mass HfO2 into a mixture interlayer achieved an optimal balance in the energy-filtering and phonon-scattering effects, obtaining a 42% enhancement in ZT over that of the Hf:ZnO matrix. The results provided a quantified guidance for designing interlayer structures in superlattice films for optimal thermoelectric performance.