Ferroelectric negative capacitance

Abstract

, which needs to be positive owing to thermodynamic stability. However, this relation is also true if one of the local effective capacitances, for example, C 1 , is negative, as long as the condition C ≥ 0 is fulfilled. In this scenario, the application of an external voltage V results in V int = V(1 + C 2 /C 1) −1 at the interface between the two dielectrics, such that V int /V > 1 if C 1 < 0. That is, NC of one part of the system enables amplification of the voltage at the interface (fig. 1b). Contrary to the usual decrease in the overall capacitance when a regular (positive) capacitance is added in series, the addition of

Stepwise internal potential jumps caused by multiple-domain polarization flips in metal/ferroelectric/metal/paraelectric/metal stack

“…Note that the resulted zigzag Q-V F characteristics is totally different from the conventional Q-V F curve in a single FE-CAP or from the S-curve expected from the original NC theory 1 . It is also significantly different from the characteristics expected from the recent models with the multiple-domain system, in which a continuous change of polarization with the help of domain wall motion is assumed [9][10][11][12][13] . Hysteresis of the V int gain is critical for achieving steep SS FETs in advanced CMOS.…”

“…Concerning NC effects in FE/PE stacks, three kinds of demonstrations have been provided experimentally so far: (i) total capacitance enhancement in the case of no internal metal between FE and PE layers [2][3][4] , (ii) transient NC effects in AC mode operation [5][6][7] , and (iii) locally stabilized NC state 8 . Several models of quasi-static NC associated with domain wall motion in a multiple-domain system have been also proposed [9][10][11][12][13] . Meanwhile, steep SS values have been demonstrated by incorporating FE/PE gate stacks into FETs with various FE materials [14][15][16] , various channel materials 15,[17][18][19] and various FET structures 14,[20][21][22][23][24] .…”

Toward Thick Piezoelectric HfO2‐Based Films

“…The discovery of ferroelectric (FE) properties in HfO 2 and ZrO 2 ‐based thin films has revived the interest in FE memories because similar films are already well established in state‐of‐the‐art high‐ k dielectrics of today's field‐effect transistors and capacitors . Beyond FE memories, significant research effort has been devoted to negative capacitance field‐effect transistors as promising solutions for future low‐power logic devices . Outside these two application fields, there has been little research effort.…”

“…[2][3][4][5] Beyond FE memories, significant research effort has been devoted to negative capacitance field-effect transistors as promising solutions for future low-power logic devices. [6][7][8] Outside these two application fields, there has been little research effort. For example, pyro-and piezoelectric applications of HfO 2 -or ZrO 2 -based films are almost plain fields.…”

Absence of critical thickness in improper ferroelectric hexagonal-YbFeO3 thin films

“…The under-screening leads to a non-zero electric field (voltage gradient) in both the ferroelectric and the dielectric layers even under the short-circuit condition (Fig. 1c), which is the source of the electrostatic energy that leads to the critical thickness of the proper ferroelectrics 21 . Eq.…”