title: Circuital characterisation of space-charge motion with a time-varying applied bias.
abstract: Understanding the behaviour of space-charge between two electrodes is important for a number of applications. The Shockley-Ramo theorem and equivalent circuit models are useful for this; however, fundamental questions of the microscopic nature of the space-charge remain, including the meaning of capacitance and its evolution into a bulk property. Here we show that the microscopic details of the space-charge in terms of resistance and capacitance evolve in a parallel topology to give the macroscopic behaviour via a charge-based circuit or electric-field-based circuit. We describe two approaches to this problem, both of which are based on energy conservation: the energy-to-current transformation rule, and an energy-equivalence-based definition of capacitance. We identify a significant capacitive current due to the rate of change of the capacitance. Further analysis shows that Shockley-Ramo theorem does not apply with a time-varying applied bias, and an additional electric-field-based current is identified to describe the resulting motion of the space-charge. Our results and approach provide a facile platform for a comprehensive understanding of the behaviour of space-charge between electrodes.
authors.affiliation: 1] School of Mechanical Engineering, Yonsei University, Seoul 120-749, Republic of Korea [2] Department of Mechanical Engineering, Kyung Hee University, Yongin 446-701, Republic of Korea.
authors.forename: Chul
authors.initials: C
authors.lastname: Kim
authors.affiliation: Department of Bioscience and Biotechnology, Sejong University, Seoul 143-747, Republic of Korea.
authors.forename: Eun-Yi
authors.initials: EY
authors.lastname: Moon
authors.affiliation: School of Mechanical Engineering, Yonsei University, Seoul 120-749, Republic of Korea.
authors.forename: Jungho
authors.initials: J
authors.lastname: Hwang
authors.affiliation: Department of Mechanical Engineering, Kyung Hee University, Yongin 446-701, Republic of Korea.
authors.forename: Hiki
authors.initials: H
authors.lastname: Hong