Varistor piezotronics: Mechanically tuned conductivity in varistors
Varistor piezotronics: Mechanically tuned conductivity in varistors
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DOI：
10.1063/1.4929360
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发表时间：
2015-08-28
影响因子：
3.2
通讯作者：
Froemling, Till
中科院分区：
文献类型：
--
作者：
Baraki, Raschid;Novak, Nikola;Froemling, Till
ZnO的压电效应最近已被研究，其目标是通过施加机械应力来修改金属/半导体肖特基势垒和p-n结。这个研究领域被称为“压电电子学”，目前主要集中在纳米结构的ZnO线。与此同时，ZnO压敏电阻材料已经被广泛使用，并可能受益于压电方法。在这种情况下，陶瓷中的晶界势垒可以通过机械应力来调节。多晶压敏电阻器在外加电场和机械场作用下电阻率发生巨大变化，为研究压电效应提供了描述性的模型系统。如果考虑到温度的影响，我们目前的机械理解可以得到质疑和证实。在本文中，我们提出了一个物理模型的基础上平行导电通路。这提供了定性和半定量的合理化的温度依赖的电性能。研究表明，狭窄的导电通路有助于整体电流，这变得越来越导电的机械应力的应用，由于降低的势垒高度。升高的温度增加了通过具有更高平均势垒的材料的其余部分的超声波电流，其几乎不受压电效应的影响。因此，在低温下，由于施加应力而引起的电阻的相对变化更大。(C)2015年AIP Publishing LLC。
The piezoelectric effect of ZnO has been investigated recently with the goal to modify metal/semiconductor Schottky-barriers and p-n-junctions by application of mechanical stress. This research area called "piezotronics" is so far focused on nano structured ZnO wires. At the same time, ZnO varistor materials are already widely utilized and may benefit from a piezotronic approach. In this instance, the grain boundary potential barriers in the ceramic can be tuned by mechanical stress. Polycrystalline varistors exhibit huge changes of resistivity upon applied electrical and mechanical fields and therefore offer descriptive model systems to study the piezotronic effect. If the influence of temperature is contemplated, our current mechanistic understanding can be interrogated and corroborated. In this paper, we present a physical model based on parallel conducting pathways. This affords qualitative and semi-quantitative rationalization of temperature dependent electrical properties. The investigations demonstrate that narrow conductive pathways contribute to the overall current, which becomes increasingly conductive with application of mechanical stress due to lowering of the barrier height. Rising temperature increases the thermionic current through the rest of the material with higher average potential barriers, which are hardly affected by the piezoelectric effect. Hence, relative changes in resistance due to application of stress are higher at low temperature. (C) 2015 AIP Publishing LLC.