Heerema S J, Schneider G F, Rozemuller M, Vicarelli L, Zandbergen H W, Dekker C
Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
Nanotechnology. 2015 Feb 20;26(7):074001. doi: 10.1088/0957-4484/26/7/074001. Epub 2015 Jan 28.
Graphene nanopores are receiving great attention due to their atomically thin membranes and intrinsic electrical properties that appear greatly beneficial for biosensing and DNA sequencing. Here, we present an extensive study of the low-frequency 1/f noise in the ionic current through graphene nanopores and compare it to noise levels in silicon nitride pore currents. We find that the 1/f noise magnitude is very high for graphene nanopores: typically two orders of magnitude higher than for silicon nitride pores. This is a drawback as it significantly lowers the signal-to-noise ratio in DNA translocation experiments. We evaluate possible explanations for these exceptionally high noise levels in graphene pores. From examining the noise for pores of different diameters and at various salt concentrations, we find that in contrast to silicon nitride pores, the 1/f noise in graphene pores does not follow Hooge's relation. In addition, from studying the dependence on the buffer pH, we show that the increased noise cannot be explained by charge fluctuations of chemical groups on the pore rim. Finally, we compare single and bilayer graphene to few-layer and multi-layer graphene and boron nitride (h-BN), and we find that the noise reduces with layer thickness for both materials, which suggests that mechanical fluctuations may be the underlying cause of the high 1/f noise levels in monolayer graphene nanopore devices.
石墨烯纳米孔因其原子级薄的膜结构和本征电学性质而备受关注，这些性质对生物传感和DNA测序似乎非常有益。在此，我们对通过石墨烯纳米孔的离子电流中的低频1/f噪声进行了广泛研究，并将其与氮化硅孔电流中的噪声水平进行了比较。我们发现，石墨烯纳米孔的1/f噪声幅度非常高：通常比氮化硅孔高两个数量级。这是一个缺点，因为它会显著降低DNA转运实验中的信噪比。我们评估了石墨烯孔中这些异常高噪声水平的可能解释。通过研究不同直径的孔在各种盐浓度下的噪声，我们发现与氮化硅孔不同，石墨烯孔中的1/f噪声不遵循胡格关系。此外，通过研究对缓冲液pH值的依赖性，我们表明噪声增加不能用孔边缘化学基团的电荷波动来解释。最后，我们将单层和双层石墨烯与少层和多层石墨烯以及氮化硼（h-BN）进行了比较，我们发现这两种材料的噪声都随层厚度降低，这表明机械波动可能是单层石墨烯纳米孔器件中高1/f噪声水平的根本原因。
