Nanoscale and macroscopic electrical ac transport along conductive domain walls in lithium niobate single crystals
Nanoscale and macroscopic electrical ac transport along conductive domain walls in lithium niobate single crystals
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DOI：
10.1088/2053-1591/1/3/035012
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发表时间：
2014-09-01
影响因子：
2.3
通讯作者：
Eng, Lukas M.
中科院分区：
文献类型：
--
作者：
Schroeder, Mathias;Chen, Xi;Eng, Lukas M.
利用纳米阻抗显微镜(NIM)研究了5摩尔%镁掺杂的NNO单晶在紫外光照射下(波长为310 nm)带电导电磁区壁(CDW)的电阻抗特性，并比较了多区和单区LNO样品的宏观复阻抗响应。与直流电导率的情况类似，观察到了比块体绝缘基质更高的电导率。由于高频下体积电容较大，DWS和BULK之间的对比在较低频率(f<；200赫兹)最为明显。此外，同时施加交流偏置和直流偏置会导致交流DW电流的实部增加。此外，还建立了精确描述磁畴和CDW贡献的等效电路，从而能够在混合导电模型的框架内分析和量化LNO中体和CDW的复杂介质导电行为。激发载流子沿CDW的跃迁是主要的电荷输运过程。
The electrical impedance properties of UV-illuminated (lambda = 310 nm) charged, conductive domain walls (CDWs) in 5 mol% magnesium-doped lithium niobate (LNO) single crystals are investigated on the nm-length scale using nanoimpedance microscopy (NIM) as well as by comparing the macroscopically measured complex impedance response between multi- and single-domain LNO samples. Similar to the case of dc conductivity, a higher conductivity of domain walls (DWs) compared to the bulk insulating matrix was observed. The contrast between DWs and bulk is most pronounced at lower frequencies (f < 200 Hz) due to the large bulk capacitance at higher frequencies. Moreover, the simultaneous application of both an ac and dc bias results in an increased real part of the ac DW current. Also, equivalent circuits accurately describing both the domain and CDW contributions were developed; as a result we are able to analyze and quantify the complex dielectric conductive behavior of both bulk and CDWs in LNO within the framework of the mixed conduction model. Hopping of excited charge carriers along the CDWs was identified as the dominant charge transport process.