Resonant domain-wall-enhanced tunable microwave ferroelectrics
Resonant domain-wall-enhanced tunable microwave ferroelectrics
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DOI：
10.1038/s41586-018-0434-2
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发表时间：
2018-08-30
期刊：
影响因子：
64.8
通讯作者：
Spanier, Jonathan E.
中科院分区：
文献类型：
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作者：
Gu, Zongquan;Pandya, Shishir;Spanier, Jonathan E.
铁电极化 (1) 的排序及其响应电场 (2) 的轨迹对于非易失性存储器 (3)、传感器 (4) 和电光器件 (5) 的操作至关重要。然而，对于电信设备中电容和频率捷变的电压控制，长期以来，畴壁一直被认为是一个障碍，因为它们会导致设备对所施加电场的响应产生高介电损耗和滞后现象(6)。为了避免这些影响，可调谐电介质通常在压电谐振条件下工作，依赖于远高于铁电居里温度(7)的操作，在该温度下可调谐性会受到影响。因此，可调介电器件的高可调性和低损耗的要求之间不可避免地存在着权衡，这导致其品质因数受到严重限制。在这里，我们表明实际上可以利用域结构来获得超低损耗和出色的频率选择性，而无需压电谐振。我们使用本质上可调的材料，其特性不仅取决于其化学成分，还取决于热力学预测的应变诱导铁电畴壁变体的接近性和可及性(8)。由此产生的千兆赫微波可调谐性和介电损耗比最好的薄膜器件好一到两个数量级，并且与块状单晶相当。由于畴壁波动，而不是通常与谐振相关的场致压电振荡，测量的品质因数超过了理论上预测的零场固有极限。在单个设备中实现了整个 L、S 和 C 微波频段（1-8 GHz）的谐振频率调谐，该范围比最好的本质可调谐材料大约 100 倍。这些结果指出了可能的纳米级域结构的丰富相空间，可用于克服电流限制，并展示了获得超高频敏捷性和低损耗微波器件的有前途的策略。
Ordering of ferroelectric polarization(1) and its trajectory in response to an electric field(2) are essential for the operation of non-volatile memories(3), transducers(4) and electro-optic devices(5). However, for voltage control of capacitance and frequency agility in telecommunication devices, domain walls have long been thought to be a hindrance because they lead to high dielectric loss and hysteresis in the device response to an applied electric field(6). To avoid these effects, tunable dielectrics are often operated under piezoelectric resonance conditions, relying on operation well above the ferroelectric Curie temperature(7), where tunability is compromised. Therefore, there is an unavoidable trade-off between the requirements of high tunability and low loss in tunable dielectric devices, which leads to severe limitations on their figure of merit. Here we show that domain structure can in fact be exploited to obtain ultralow loss and exceptional frequency selectivity without piezoelectric resonance. We use intrinsically tunable materials with properties that are defined not only by their chemical composition, but also by the proximity and accessibility of thermodynamically predicted strain-induced, ferroelectric domain-wall variants(8). The resulting gigahertz microwave tunability and dielectric loss are better than those of the best film devices by one to two orders of magnitude and comparable to those of bulk single crystals. The measured quality factors exceed the theoretically predicted zerofield intrinsic limit owing to domain-wall fluctuations, rather than field-induced piezoelectric oscillations, which are usually associated with resonance. Resonant frequency tuning across the entire L, S and C microwave bands (1-8 gigahertz) is achieved in an individual device-a range about 100 times larger than that of the best intrinsically tunable material. These results point to a rich phase space of possible nanometre-scale domain structures that can be used to surmount current limitations, and demonstrate a promising strategy for obtaining ultrahigh frequency agility and low-loss microwave devices.