Integration of Hf-based ferroelectric materials into the MOSFET gate stack introduces new physics that potentially enables continued scaling for both CMOS and memory devices. The electrostatic potential amplification effect arises when the device is engineered to depolarize and hence stabilize the ferroelectric negative capacitance state, which eliminates the ferroelectric hysteresis and enhances the gate control. On the other hand, when the ferroelectric layer is thick enough to overcome the depolarization field, non-volatile memory function can be realized through the remnant polarization states. Such systems exhibit process and structural compatibility with CMOS technology and thus are of significant application relevance. Experiments have demonstrated low-voltage operations for both types of devices, showing promising prospects for next-generation logic devices with high reliability.

To harness the effects for designing the NCFET and FeFET devices, it is important to understand the behaviours of the ferroelectric layer in the relevant states. In this dissertation, the polarization responses of negative capacitance states are modeled from different aspects through self-consistent device and circuit models that are calibrated to experimental measurements. First, the 101-stage ring oscillator consisting of 14 nm FinFET devices with a ferroelectric gate layer that exhibits negative capacitance are used to study the response speed of the negative capacitance effect. The consistency of the device DC characteristics and the circuit oscillations with less than 10ps per-stage delay confirm the fast negative capacitance response. Next, NCFET device characteristics and scaling trends that are unexpected by conventional theory were explained with non-linear negative capacitance responses as described by the Landau's phenomenology. Design insights are drawn, and the observation bodes well for extending the MOSFET gate length scaling limit. Finally, high-speed NCFET RF operations are projected and designed based on experimental characterization results and Monte-Carlo transport simulations. Silicon-channel NCFETs are expected to achieve cutoff frequency over 400GHz with standard SOI device structures and over 650GHz with air-gap spacers.

The carrier dynamics of memory program and readout operations for an n-type SOI FeFET are studied through TCAD simulations. Gate-induced drain leakages during the program operation with large negative gate biases can result in excessive hole concentrations with lifetime exceeding microseconds during the hold phase. While the excess holes result in approximately 100ps delay in the readout phase before a large read margin can be detected, it benefits the program speed and the quasi-steady-state read margin. Therefore, such effects can be utilized for low-power memory applications through proper SOI FeFET designs with the awareness of excess carrier dynamics.

An adult-like concept of intention includes a deliberate action to achieve a goal and a belief that one’s action (if successful) will cause the desired outcome. For example, good outcomes caused by accident or by chance are not believed to be caused intentionally. In two experiments, we asked whether children understand this connection between intentions and outcomes. Children played two games in which actions could produce unintended outcomes (i.e., causes were unplanned). Children sometimes received a desirable reward independent of intention. In Experiment 1, 4- and 5-year- olds mistakenly claimed they had intended the desirable outcome even when it was unexpected. Four-year-olds judged that they had not intended a deliberate action if it did not yield a rewarding out- come. Experiment 2 demonstrates that 6-year-olds seldom make these errors. The results suggest that 4- and 5-year-old children have not yet attained an adult-like concept of intention. Their inac- curate judgments regarding their intentions, given a rewarding yet unexpected outcome, can be explained by a positivity bias.

The current study employed a modified gambling task, in which probabilistic cues were provided to elicit positive or negative expectations. Event-related potentials (ERPs) to ‘‘final outcome’’ and ‘‘probabilistic cues’’ were analyzed. Difference waves between the negative condition and the corresponding positive condition were examined. The results confirm that feedback related negativity (FRN) amplitude is modulated by the interaction of outcome valence and expectancy by showing larger FRN difference waves for unexpected than expected outcomes. More interestingly, the difference wave between ERPs elicited by positive and negative expectations showed a negative deflection, with a frontal midline source density around 280 ms after onset of the predictive cue. Negative expectations were associated with larger FRN amplitudes than positive expectations. This suggests that FRN is elicited by probabilistic cues to pending outcomes.