Dynamics Of Glassy Materials Research Articles

Mechanisms and models of interface trap annealing in positively-biased MOS devices

Abstract We propose a hydrogen anion (H$^-$) passivation mechanism of the interface trap annealing (ITA) in positively-biased metal-oxide-semiconductor (MOS) devices. It is demonstrated that, the protons (H$^+$) released in SiO$_2$ due to H$_2$ cracking on oxide traps can migrate into Si at relatively high temperature, therefore passivating the interfacial $P_b$ centers by capturing two electrons provided by the positive bias. This new mechanism explains the elimination temperature of about 100$^\circ$C in experiments, which is much lower than temperature above 220$^\circ$C predicted by the traditional H$_2$ passivation mechanism. We also derive analytic models of the ITA, based on the coupling transformation dynamics of oxide and interface traps, as well as the concept of hierarchically constrained dynamics in glassy materials. These models can universally describe a generation-to-elimination transition of $P_b$, and predict the enhanced elimination of $E'_\gamma$ as the annealing temperature is elevated. Moreover, we demonstrate that, the defect annealing models can be applied to analysis the nonmonotonic temperature dependence of the annealing of threshold voltage shift in nMOS devices. Our findings provide a theoretical basis for achieving the low temperature elimination of interface traps, and for setting the high temperature stages of accelerated aging and damage evaluations of MOS devices.

Hyperuniform Density Fluctuations and Diverging Dynamic Correlations in Periodically Driven Colloidal Suspensions

The emergence of particle irreversibility in periodically driven colloidal suspensions has been interpreted as resulting either from a nonequilibrium phase transition to an absorbing state or from the chaotic nature of particle trajectories. Using a simple model of a driven suspension, we show that a nonequilibrium phase transition is accompanied by hyperuniform static density fluctuations in the vicinity of the transition, where we also observe strong dynamic heterogeneities reminiscent of dynamics in glassy materials. We find that single particle dynamics becomes intermittent and strongly non-Fickian, and that collective dynamics becomes spatially correlated over diverging length scales. Our results suggest that the two theoretical scenarii can be experimentally discriminated using particle-resolved measurements of standard static and dynamic observables.

Plasticity of a colloidal polycrystal under cyclic shear.

We use confocal microscopy and time-resolved light scattering to investigate plasticity in a colloidal polycrystal, following the evolution of the network of grain boundaries as the sample is submitted to thousands of shear deformation cycles. The grain boundary motion is found to be ballistic, with a velocity distribution function exhibiting nontrivial power law tails. The shear-induced dynamics initially slow down, similarly to the aging of the spontaneous dynamics in glassy materials, but eventually reach a steady state. Surprisingly, the crossover time between the initial aging regime and the steady state decreases with increasing probed length scale, hinting at a hierarchical organization of the grain boundary dynamics.

Minimal model for kinetic arrest

To elucidate slow dynamics in glassy materials, we introduce the figure-8 model in which N hard blocks undergo Brownian motion around a circuit in the shape of a figure 8. This system undergoes kinetic arrest at a critical packing fraction phi=phi g<1 , and for phi approximately phi g long-time diffusion is controlled by rare, cooperative, "junction-crossing" particle rearrangements. We find that the average time between junction crossings tau JC, and hence the structural relaxation time, does not simply scale with the configurational volume Omega c of transition states, because tau JC also depends on the time to complete a junction crossing. The importance of these results in understanding cage-breaking dynamics in glassy systems is discussed.

Dynamics of glassy materials by high resolution inelastic X-ray scattering

Dynamics of glassy materials by high resolution inelastic X-ray scattering

Optical basicities and structural dynamics in glassy materials

Optical basicities and structural dynamics in glassy materials

Optical basicities and structural dynamics in glassy materials

There is a general question within the theory of optical basicity, which is why basicities determined by probe cations (typically Tl + and Pb 2+) fail to lie on the ‘theoretical’ curve linking the average basicity to glass composition. An explanation for this discrepancy is presented here, based in part on the ‘two-site’ model of Kamitsos et al. and on a dynamic site model which assumes that mobile ions (Li +, Na +, etc.) create their own sites lying along the pathways for ion migration. The experimental spread in optical basicities is attributed to this dynamic structure, and the ‘hole-digging’ capabilities of both host and probe cations. Mobile ions in singly-occupied ‘double sites’ are in relatively shallow energy wells (the L-sites), while those in doubly-occupied double sites are in relatively deep energy wells (the H-sites). Probe cations enter both H- and L-sites when their motions become coupled to those of the host cations.

Dynamics of glassy materials as studied by neutrons

Many unsolved riddles in the glassy state of matter seem to be connected with the low-frequency excitations in the meV range. This frequency range can be conveniently studied by neutron spectroscopy. The present stage of these investigations is reviewed. It reveals the coexistence of sound waves and soft quasilocalized vibrations with a crossover to structural relaxations at the low-frequency end. The possible connection to the two-level states dominating glassy properties below 1 K is discussed.