名义上静默的BiFeO3畴壁中意外的巨微波电导
Unexpected Giant Microwave Conductivity in a Nominally Silent BiFeO3 Domain Wall
摘要：
近年来，基于铁电畴壁的纳米电子器件，如存储器、晶体管和整流器，已经被证明是可行的。另一方面，实际的高速电子设备通常需要千兆赫兹（GHz）范围内的操作频率，其中偶极振荡的影响是重要的。在这项工作中，在某些BiFeO 3 DW中观察到103 S/m量级的意想不到的巨大GHz电导率，这比相同壁的载流子诱导直流电导率大约100，000倍。令人惊讶的是，DWs的标称配置排除了在垂直于表面的激励电场下的交流传导。理论分析表明，倾斜DW在薄膜表面附近受到不对称的应力，而对照样品中的垂直壁则不然。由此产生的不平衡的极化轮廓，然后可以耦合到平面外的微波场，并诱导功率耗散，这是由相场建模证实。由于在微波电路中，载流子传导和束缚电荷振荡对交流电导率的贡献是等效的，因此对局域结构动力学的研究可能为实现DW纳米器件的射频应用开辟一条新的途径。
英文摘要：
Nanoelectronic devices based on ferroelectric domain walls (DWs), such as memories, transistors, and rectifiers, have been demonstrated in recent years. Practical high-speed electronics, on the other hand, usually demand operation frequencies in the giga-Hertz (GHz) regime, where the effect of dipolar oscillation is important. In this work, an unexpected giant GHz conductivity on the order of 103 S/m is observed in certain BiFeO3 DWs, which is about 100,000 times greater than the carrier-induced dc conductivity of the same walls. Surprisingly, the nominal configuration of the DWs precludes the ac conduction under an excitation electric field perpendicular to the surface. Theoretical analysis shows that the inclined DWs are stressed asymmetrically near the film surface, whereas the vertical walls in a control sample are not. The resultant imbalanced polarization profile can then couple to the out-of-plane microwave fields and induce power dissipation, which is confirmed by the phase-field modeling. Since the contributions from mobile-carrier conduction and bound-charge oscillation to the ac conductivity are equivalent in a microwave circuit, the research on local structural dynamics may open a new avenue to implement DW nano-devices for RF applications.
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