Percolation transition in the gas-induced conductance of nanograin metal oxide films with defects
Percolation transition in the gas-induced conductance of nanograin metal oxide films with defects
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DOI：
10.1063/1.4809572
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发表时间：
2013-06-14
影响因子：
3.2
通讯作者：
Bunde, Armin
中科院分区：
文献类型：
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作者：
Draeger, Julia;Russ, Stefanie;Bunde, Armin
我们采用蒙特-卡罗模拟方法，通过位键逾渗模型，研究了烧结金属氧化物纳米颗粒薄膜中气体诱导电子俘获/释放所产生的电导开关。我们探索基于这些机制的气体传感器的可能性。在我们的研究中，我们模拟不同厚度的薄膜，其中的颗粒（网站）和这些颗粒之间的接触（债券）的电导值取决于从环境大气中吸附的气体分子的表面密度N-r。低于临界密度N-r = N-r，N-c时，系统由于电流中断而绝缘，电流通过连接键或颗粒内部。这导致两个竞争的临界气体覆盖阈值N-r，c（（键））和N-r，c（（位点）），分别将绝缘与导电相分离。对于N-r，c（（site））> N-r，c（（bond）），单分散传感器的特征曲线在N-r = N-r，c（（site））处显示出从零到有限电导的显著跳跃，而对于多分散传感器，位点渗滤效应将跳跃修改为特征曲线的急剧增加，从而导致灵敏度的增强。对于N-r，c（（site））< N-r，c（（bond）），单分散和多分散体系都遵循相同的曲线，其显示出更平滑的特征增加α（N-r - N-r，c（（bond）（2），这表明，尽管发生了接近N-r，N-c的固有键渗透效应，但键的增加是主导效应。(C)2013 AIP Publishing LLC.
We use Monte-Carlo Simulations to study the conductance switching generated by gas-induced electron trapping/-releasing in films of sintered metal oxide nanoparticles by using a site-bond percolation model. We explore the possibilities of gas sensors based on these mechanisms. In our study, we model films of different thicknesses where the conductance values of the grains (sites) and of the contacts (bonds) between these grains depend on the surface density N-r of adsorbed gas molecules from the ambient atmosphere. Below a critical density N-r = N-r,N-c, the system is insulating due to the interruption of current flow, either through the connecting bonds or through the grain interior. This leads to two competing critical gas covering thresholds N-r,c((bond)) and N-r,c((site)), respectively, that separate the insulating from the conducting phase. For N-r,c((site)) > N-r,c((bond)), the characteristic curve of monodisperse sensors shows a noticeable jump from zero to a finite conductance at N-r = N-r,c((site)), while for polydisperse sensors site percolation effects modify the jump into a steep increase of the characteristic curve and thus lead to an enhanced sensitivity. For N-r,c((site)) < N-r,c((bond)), both mono- and polydisperse systems follow the same curves that show a smoother characteristic increase alpha (N-r - N-r,c((bond)))(2) which reveals that, despite the occurrence of an inherent bond percolation effect close to N-r,N-c, the increase of the bonds is the dominating effect. (C) 2013 AIP Publishing LLC.