Simultaneous estimation of spatially distributed electrical conductivity and unknown contact impedances for imaging single layer graphene using electrical impedance tomography
A. K. Khambampati, S. K. Sharma, S. A. Rahman, W. Y. Kim, K. Y. Kim
Department of Electronic Engineering, Jeju National University, South Korea, 63243
Graphene which is a 2D material possesses great mechanical and electrical properties that makes it an ideal material for development of novel device applications. Growing large area graphene is very challenging and achieving homogenous high-quality graphene is highly influenced by instrument and handing conditions. Conductivity characterization of graphene in a non-destructive way is essential to determine its electrical behaviour. For the application of electrical impedance tomography to graphene conductivity imaging the high conductive nature of graphene poses great challenge. The electrodes contact impedance are not constant and may change due to interaction of atmosphere with adhesives that are used to connect the graphene sample with external terminals. Estimating the unknown contact impedance of electrode can be helpful in determining true conductivity profile of graphene. Therefore, in this paper, we tried to estimate the contact impedances simultaneously with conductivity of graphene sample. Complete electrode model is used as a physical model to describe the voltage measurements and using a nonlinear algorithm contact impedances are estimated. Using the estimated contact impedance of electrodes, spatial conductivity distribution across graphene surface is estimated. Numerical experiments are carried out on a square shaped single layer graphene wafer of size 2.5cm. The results show that the proposed method could estimate the contact impedance at each electrode with good accuracy and the estimated contact impedances have resulted in improved absolute estimates of conductivity distribution.
Keywords: Electrical impedance tomography, conductivity imaging, contact impedance, inverse problem, absolute imaging
Industrial Application: General
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