skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Unveiling the Apparent “Negative Capacitance” Effects Resulting from Pulse Measurements of Ferroelectric-Dielectric Bilayer Capacitors
Title: Unveiling the Apparent “Negative Capacitance” Effects Resulting from Pulse Measurements of Ferroelectric-Dielectric Bilayer Capacitors
Apparent ‘Negative Capacitance’ (NC) effects have been observed in some ferroelectric-dielectric (FE-DE) bilayers by pulse measurements, and the associated results have been published that claim to be direct evidence to support the quasi-static ‘negative capacitance’ (QSNC) idea. However, the ‘NC’ effects only occur when sufficiently high voltage is applied, and even exist in stand-alone FE capacitors. These results contradict the QSNC theory, as it predicts that once stabilized (requires a DE layer), the FE remains in the ‘NC’ state regardless of the applied voltage. In this letter, by the use of Nucleation-Limited-Switching (NLS) model, we present our results obtained from simulation of pulse measurements on samples that are similar to the published ones. The simulation results indicate that reverse polarization switching occurs upon the falling edge of the pulses, which leads to the apparent hysteresis-free NC effect. This work provides an alternative interpretation of the experimental results without invoking the QSNC theory.  more » « less
Award ID(s):
1941316
PAR ID:
10207151
Author(s) / Creator(s):
; ; ;
Editor(s):
Naeemi, A.J.
Date Published:
Journal Name:
IEEE electron device letters
Volume:
41
Issue:
10
ISSN:
1558-0563
Page Range / eLocation ID:
1492-95
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, IEEE Transactions on Electron Devices)
    While negative capacitance (NC) has been demonstrated in ferroelectric-dielectric (FE-DE) heterostructures in the form of capacitance enhancement, all experimental evidence, to date, suggests the existence of domains therein. Here, we address the question: what are the conditions to achieve ideal, domain-free NC in FE-DE heterostructures? Our main claim is that for given thicknesses of the ferroelectric and the dielectric layers, there is a critical value of domain wall energy parameter— above which the system would be stabilized in an ideal and robust domain-free NC state and would be robust against domain formation. Our analyses suggest that to achieve ideal NC, efforts should lie in understanding the means to control the domain wall energy on all fronts, both theory and experiments via high throughput design, discovery, and engineering of ferroelectrics. 
    more » « less
  2. ; ; ; ; (, Journal of Vacuum Science & Technology A)
    High voltage nanosecond pulse driven electric discharges in de-ionized water with an argon bubble suspended between two electrodes were experimentally investigated. Two electrode configurations were used to temporally resolve the time scales of the discharge from the applied voltage rise time (7 ns), through the end of the first pulse (∼30 ns), and longer (>50 ns). We found that, in positive and negative applied voltage polarities, discharge initiates in the water at the tip of the anode. The discharge in the water rapidly extends (∼104 m/s) to the apex of the bubble and light emitted from inside the bubble begins to form. The steep rate of rise of the applied voltage (dV/dt<4 kV/ns) and the short time for the development of discharge in the water suggest that cavitation is a likely mechanism for discharge initiation and propagation in water. In addition, the short duration of the applied voltage pulse results in only a partial Townsend discharge inside the bubble. 
    more » « less
  3. ; ; ; ; ; ; ; ; (, npj 2D Materials and Applications)
    Abstract The device concept of ferroelectric-based negative capacitance (NC) transistors offers a promising route for achieving energy-efficient logic applications that can outperform the conventional semiconductor technology, while viable operation mechanisms remain a central topic of debate. In this work, we report steep slope switching in MoS2transistors back-gated by single-layer polycrystalline PbZr0.35Ti0.65O3. The devices exhibit current switching ratios up to 8 × 106within an ultra-low gate voltage window of$$V_{{{\mathrm{g}}}} = \pm \! 0.5$$ V g = ± 0.5 V and subthreshold swing (SS) as low as 9.7 mV decade−1at room temperature, transcending the 60 mV decade−1Boltzmann limit without involving additional dielectric layers. Theoretical modeling reveals the dominant role of the metastable polar states within domain walls in enabling the NC mode, which is corroborated by the relation between SS and domain wall density. Our findings shed light on a hysteresis-free mechanism for NC operation, providing a simple yet effective material strategy for developing low-power 2D nanoelectronics. 
    more » « less
  4. ; ; (, 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA))
    Multilevel modular resonant switched-capacitor converter can achieve either zero-current switching (ZCS) or zero-voltage switching (ZVS) by utilizing different converter control strategies. This paper presents a comprehensive way to compare the root mean square (RMS) value of current flowing through switching devices in both ZCS operation and ZVS operation. The study shows that with appropriate converter parameter design, the ZVS operation allows the RMS value of switch current at most 10% lower than that in ZCS operation. Therefore, the converter operating at ZVS mode has the potential to achieve higher efficiency comparing to the converter that operates at ZCS mode due to less semiconductor conduction loss. Furthermore, the ZVS operation can reduce the power loss due to MOSFET output capacitance. A 6x converter with 54V input voltage, 9V output voltage and 600W power rating is used as an example to show the detailed design procedure. Simulation results are provided to verify the theoretical analysis. Also, a 600W lab prototype that has 6 to 1 voltage conversion ratio has been built to verify the theoretical analysis. 
    more » « less
  5. ; ; ; ; (, International Electron Device Meetings)
    We present a physics-based model for ferroelectric/negative capacitance transistors (FEFETs/ NCFETs) without an inter-layer metal between ferroelectric and dielectric in the gate stack. The model self-consistently solves 2D Poisson's equation, non-equilibrium Green's function (NEGF) based charge and transport equations, and multi-domain Landau Khalatnikov (LK) equations with the domain interaction term. The proposed simulation framework captures the variation of ferroelectric (FE) polarization (P) along the gate length due to non-uniform electric field (E) along the channel. To calibrate the LK equations, we fabricate and characterize 10nm HZO films. Based on the calibrated model, we analyze the gate/drain voltage dependence of P distribution in the FE and its effect on the channel potential and current-voltage characteristics. Our results highlight the importance of larger domain interaction to boost the benefits of FEFETs with subthreshold swing (SS) as small as ~50mV/decade achieved at room temperature. As domain interaction increases, the characteristics of FEFETs without inter-layer metal (SS, negative drain induced barrier lowering (DIBL), negative output conductance) approach those of FEFETs with inter-layer metal. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email