Effects of charge collectors in ferroelectric E-field sensors

Abstract

A nonlinear dynamical system based on ferroelectric capacitors coupled into a unidirectional ring circuit, which under particular conditions exhibits an oscillating regime of behavior, is considered with particular interest for developing novel electric field sensors. For such a device a weak, external, target electric field interacts with the system thus inducing perturbation of the polarization of the ferroelectric material; the target signal can be indirectly detected and quantified via its effect on the system response. The conceived devices exploit the synergetic use of bistable ferroelectric materials, micromachining technologies that allow us to address charge density amplification, and implement novel sensing strategies based on coupling non-linear elemental cells. The "charge collector" strategy, already discussed in [1], has been employed to detect the target field. An experimental characterization of the whole circuit, including three cells coupled in a ring configuration, has been carried out. The effect of the dimensions of the charge collectors has also been investigated.Keywords-Non linear dynamical system, ferroelectric capacitor, hysteresis, quartic double-well potential, quasistatic electric field (E-field) sensors, Sawyer-Tower (ST) circuit.

A Nonlinear Electric Field Sensor That Exploits Coupled Oscillator Dynamics: The Charge Collection Mechanism

“…1(a). This system behaves according to the theory of unidirectionally coupled nonlinear circuits: An odd number (N ≥ 3) of nonlinear dynamic cells connected in a ring configuration [35], [39]- [41] can operate in an auto-oscillating regime. In particular, such a regime occurs when the coupling strength λ between contiguous cells crosses a threshold value.…”

“…In particular, an ac target E-field with frequency ω E will produce a modulation of the oscillating signal generated by the coupled circuit [34], [39].…”

“…Coupling between contiguous cells takes place by gain blocks (from which one obtains the coupling strength λ). A dedicated integrated FE capacitor with a third central electrode, hereinafter referred to as the "sensing electrode," has been designed; the latter has to be connected to an external plate, the "charge collector," to amplify the effect of the target field on the FE polarization [34], [39]. Capacitors with different dimensions of the sensing region have been designed by the Integrated Circuit Layout Editor [43].…”

“…The theoretical treatment has been validated by experimental results confirming the suitability of the proposed methodology. A nonlinear dynamical system based on FE capacitors coupled into a unidirectional ring circuit is considered in this paper with particular interest for developing novel E-field sensors [39]. When the coupling gain between consecutive cells of the ring exceeds a well-defined threshold, the system transitions to an oscillating regime [35] in the response variable (the polarization) of each element.…”

“…In recent work [34]- [39], the authors have presented the idea of innovative E-field sensing solutions based on nonlinear coupled oscillators with hysteretic elements. In particular, in [34], a single nonlinear dynamic device employing a ferroelectric (FE) capacitor to measure quasi-static E-fields has been discussed.…”