title: Alternative interpretations for decreasing voltage with increasing charge in ferroelectric capacitors.
abstract: Recent claim on the direct observation of a negative capacitance (NC) effect from a single layer epitaxial Pb(Zr0.2,Ti0.8)O3 (PZT) thin film was carefully reexamined, and alternative interpretations that can explain the experimental results without invoking the NC effect are provided. Any actual ferroelectric capacitor has an interfacial layer, and experiment always measures the sum of voltages across the interface layer and the ferroelectric layer. The main observation of decreasing ferroelectric capacitor voltage (VF) for increasing ferroelectric capacitor charge (QF), claimed to be the direct evidence for the NC effect, could be alternatively interpreted by either the sudden increase in the positive capacitance of a ferroelectric capacitor or decrease in the voltage across the interfacial layer due to resistance degradation. The experimental time-transient VF and QF could be precisely simulated by these alternative models that fundamentally assumes the reverse domain nucleation and growth. Supplementary experiments using an epitaxial BaTiO3 film supported this claim. This, however, does not necessarily mean that the realization of the NC effect within the ferroelectric layer is impractical under appropriate conditions. Rather, the circuit suggested by Khan et al. may not be useful to observe the NC effect directly.
authors: Department of Material Science &Engineering and Inter university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea.
authors: Seul Ji
authors: SJ
authors: Song
authors: Department of Material Science &Engineering and Inter university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea.
authors: Yu Jin
authors: YJ
authors: Kim
authors: Department of Material Science &Engineering and Inter university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea.
authors: Min Hyuk
authors: MH
authors: Park
authors: Department of Material Science &Engineering and Inter university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea.
authors: Young Hwan
authors: YH
authors: Lee
authors: Department of Material Science &Engineering and Inter university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea.
authors: Han Joon
authors: HJ
authors: Kim
authors: Department of Material Science &Engineering and Inter university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea.
authors: Taehwan
authors: T
authors: Moon
authors: Department of Material Science &Engineering and Inter university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea.
authors: Keum
authors: K
authors: Do Kim
authors: Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea.
authors: Jung-Hae
authors: JH
authors: Choi
authors: State Key Laboratory of ASIC &System, School of Microelectronics, Fudan University, Shanghai 200433, China.
authors: Zhihui
authors: Z
authors: Chen
authors: State Key Laboratory of ASIC &System, School of Microelectronics, Fudan University, Shanghai 200433, China.
authors: Anquan
authors: A
authors: Jiang
authors: Department of Material Science &Engineering and Inter university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea.
authors: Cheol Seong
authors: CS
authors: Hwang