Puczkarski Paweł, Wu Qingqing, Sadeghi Hatef, Hou Songjun, Karimi Amin, Sheng Yuewen, Warner Jamie H, Lambert Colin J, Briggs G Andrew D, Mol Jan A
Department of Materials , University of Oxford , 16 Parks Road , Oxford OX1 3PH , United Kingdom.
Department of Physics , Lancaster University , Bailrigg , Lancaster LA1 4YB , United Kingdom.
ACS Nano. 2018 Sep 25;12(9):9451-9460. doi: 10.1021/acsnano.8b04713. Epub 2018 Aug 20.
Graphene tunnel junctions are a promising experimental platform for single molecule electronics and biosensing. Ultimately their noise properties will play a critical role in developing these applications. Here we report a study of electrical noise in graphene tunnel junctions fabricated through feedback-controlled electroburning. We observe random telegraph signals characterized by a Lorentzian noise spectrum at cryogenic temperatures (77 K) and a 1/ f noise spectrum at room temperature. To gain insight into the origin of these noise features, we introduce a theoretical model that couples a quantum mechanical tunnel barrier to one or more classical fluctuators. The fluctuators are identified as charge traps in the underlying dielectric, which through random fluctuations in their occupation introduce time-dependent modulations in the electrostatic environment that shift the potential barrier of the junction. Analysis of the experimental results and the tight-binding model indicate that the random trap occupation is governed by Poisson statistics. In the 35 devices measured at room temperature, we observe a 20-60% time-dependent variance of the current, which can be attributed to a relative potential barrier shift of between 6% and 10%. In 10 devices measured at 77 K, we observe a 10% time-dependent variance of the current, which can be attributed to a relative potential barrier shift of between 3% and 4%. Our measurements reveal a high sensitivity of the graphene tunnel junctions to their local electrostatic environment, with observable features of intertrap Coulomb interactions in the distribution of current switching amplitudes.
石墨烯隧道结是单分子电子学和生物传感领域一个很有前景的实验平台。最终，它们的噪声特性将在这些应用的开发中发挥关键作用。在此，我们报告了一项关于通过反馈控制电灼制备的石墨烯隧道结中电噪声的研究。我们观察到，在低温（77K）下，随机电报信号具有洛伦兹噪声谱特征；在室温下，则具有1/f噪声谱特征。为了深入了解这些噪声特征的起源，我们引入了一个理论模型，该模型将量子力学隧道势垒与一个或多个经典涨落源耦合。涨落源被确定为底层电介质中的电荷陷阱，其占据情况的随机涨落在静电环境中引入了随时间变化的调制，从而改变了结的势垒。对实验结果和紧束缚模型的分析表明，随机陷阱占据情况受泊松统计支配。在室温下测量的35个器件中，我们观察到电流随时间的变化率为20% - 60%，这可归因于相对势垒偏移6%至10%。在77K下测量的10个器件中，我们观察到电流随时间的变化率为10%，这可归因于相对势垒偏移3%至4%。我们的测量结果揭示了石墨烯隧道结对其局部静电环境具有高度敏感性，在电流切换幅度分布中存在可观测的陷阱间库仑相互作用特征。
