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Several experimental studies are conducted to explain the impact of the electrical properties and structural relaxation (SR) of the chalcogenide materials on the phase-change memory (PCM) cells. A high current or high voltage readout is shown to highly improve the resistance stability of the system.

The article presents and examines a new physical model, which is employed to demonstrate the impact of structural relaxation (SR) of the chalcogenide materials on the reliability of phase-change memory (PCM) cells. The defect annihilation dynamics is also shown to be highly affected by the electrical characteristics of the cells.

Several studies are conducted to explain the kinetics and mechanisms involved in the multilevel programming operation taking place in the programmable metallization cell (PMC) memory. A combination of the voltage-driven ion migration and electrochemical deposition is shown to lead to the discussed programming operation.

A thermal-dissolution model for reset transition in unipolar resistive-switching memory (RRAM) based on metal oxides is presented. The model based on Joule heating and dissolution of the conductive filament (CF) could be used to study the reduction of the reset current required for device application.

The characterization of the electrical and thermal conduction properties of the low-resistance state of the conductive filament (CF) and the physical mechanism for the switching from low- to high-resistance state of NiO-based resistive-switching memory (RRAM) devices is reported. The results from the evaluation of the thermal resistance of the CF and the activation energy for the dissolution mechanism could be used to design a physics-based numerical model for the reset operation based on CF thermal breakup.

A novel mixed-scaling approach for phase-change memory (PCM) cells is discussed. Findings reveal that the proposed approach is capable of providing the maximum decrease of programming current compatible with the reliability requirements deriving from the thermal crosstalk.

The programming and read performances of phase-change memory (PCM) cells are examined. The tradeoff between the needs of low programming current and low set resistance is addressed.

A new physics-based statistical model is described for random telegraph noise in Flash memories. This model has analyzed the oxide defects responsible for the random telegraph noise, allowing a spatial and energetic localization of the traps involved in the threshold-voltage instability process.

An analytical physical-based model for N/G parameters extraction and retention lifetime extrapolation is proposed. The impact of N/G parameters is addressed to explore the improvements of next generation phase-change memory (PCM) reliability by material optimization.

The drift and recovery transient of threshold voltage and resistance after reset are studied using time-resolved analysis. The recovery mechanism is described using the recombination of excess carriers in the amorphous chalcogenide, and the impact on the readout and verify operation of the memory device are also addressed.

A detailed analysis of data retention statistics in phase-change memories is presented and the experimental results are discussed with the aid of a Monte Carlo model for crystallization that allows a statistical approach. The physically based crystallization-percolation model can account for temperature dependence of data loss and its statistical spread, and in particular, this dependence is given by an increase of the crystallite radius, consistently with nucleation and growth theory.

A physically based model for data loss in phase-change memories, where chalcogenide crystallization is simulated by Monte Carlo approach, assuming homogenous nucleation in the amorphous-phase volume is presented. The Monte Carlo model allows a statistical analysis of data loss as a function of both geometry properties like amorphous thickness, contact area, amorphous volume and crystalline gain size, and electrical properties such as resistivity ratio between the crystalline and amorphous phase.

This paper proposes an extensive analysis of multiphase LC oscillators. N oscillators coupled in a ring topology can generate multiphase outputs. For their nature, these oscillators operate off-resonance and consequently their phase noise worsens at increasing coupling strength. Since the coupling transistors raise the total power consumption, the noise-power product degrades even more with respect to a stand-alone oscillator. On the other hand, at high coupling factors, component mismatches affect less the phase accuracy. Closed-form expressions for phase noise and phase accuracy are derived which are verified against circuit simulations. Index Terms--Coupled oscillators, image rejection, multiphase clock, phase accuracy, phase noise, quadrature oscillators, RF front-end, voltage-controlled oscillators.

This paper presents a complete analysis of the effect of mismatches in linear amplification with nonlinear components transmitters for orthogonal frequency-division multiplexing modulated signals. Gain and phase imbalances between the two amplification paths can severely degrade the linearity performance introducing both out-of-band spectral regrowth and in-band distortion. Analytical expressions are derived to readily evaluate the contribution of mismatches to the adjacent-channel power ratio and error vector magnitude of the transmitter. A direct evaluation of the matching requirements can thus be obtained from the linearity specifications, without the need of time-consuming simulations. Index Terms--Amplifier linearization, mobile communications, outphasing transmitter, RF power amplifier, wireless local area network (LAN).