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This study investigates the physical processes involved in picosecond pulse (20-28 ps FWHM) laser ablation of Al 6061, 316L stainless steel, and undoped crystalline Si (〈100〉) over a range of laser wavelength (355 nm and 1064 nm) and fluence (0.1-40 J/cm2). Experimental measurements of material ablation rate show enhanced removal at the 355 nm wavelength, primarily due to laser-plasma interaction (LPI) within the ablative plume that approaches an order of magnitude increase over the measured removal at 1064 nm. A transition in the ablation rate at 355 nm is identified around ∼10 J/cm2 above which the removal efficiency increases by a factor of two to three. Multi-physics radiation hydrodynamic simulations, considering LPI effects and utilizing a novel mixed-phase equation of state model, show that the transition in ablation efficiency is due to the onset of melt ejection through cavitation, where laser-driven shock heating sets the depth of melt penetration and the ensuing release wave from the ablation surface drives cavitation through the imposition of tensile strain within the melt. High-speed pump-probe imaging of the ejecta and ejecta collection studies, as well as scanning electron microscopy of the ablation craters, support the proposed cavitation mechanism in the higher fluence range. The ablation process is critically influenced by LPI effects and the thermophysical properties of the material. [ABSTRACT FROM AUTHOR]

For pulse lengths between 1 and 60 ps, laser-induced modifications of optical materials undergo a transition from mechanisms intrinsic to the materials to defect-dominated mechanisms. Elucidating the location, size, and identity of these defects will greatly help efforts to reduce, mitigate, or eliminate these defects. We recently detailed the role of defects in the ps laser-modifications of silica coatings. We now discuss the similar role of defects in HfO2 1/2-wave coatings and also include the environmental effects on the damage process. By switching between S and P polarizations, we distinguish the effects of defects at the surface from those throughout the material. We find that defects very near the surface are dependent on the environment, leading to worse damage in vacuum than in air. Air suppresses or lessens the effects of these defects, suggesting a photo-chemical component in the mechanism of laser damage in HfO2 coatings. [ABSTRACT FROM AUTHOR]

The impact of program/erase (P/E) cycling on drain disturb in NOR flash EEPROM cells under channel hot electron (CHE) and channel-initiated secondary electron (CHISEL) programming operation is studied. The charge gain disturb increases and charge loss disturb decreases after cycling under CHE and CHISEL operation.

The origin of drain disturb in NOR Flash EEPROM cells under channel initiated secondary electron (CHISEL) programming operation is identified. It is presented that methods for improving CHISEL programming performance (higher channel doping and/or lower drain junction depth or halo) increase drain disturb, which has to be carefully considered for efficient design of scaled cells.

Channel initiated secondary electron (CHISEL) injection programming for NOR Flash electrically erasable programmable read-only memories (EEPROM) is examined and discussed.

The generation of interface states and stress-induced leakage current during channel hot electron stress experiments in the context of a possible hydrogen/deuterium isotope effect is analyzed in detail. The results show that generation of interface states is related to the hydrogen release at the Si-SiO2 at a relatively high voltage, where a large isotope effect is found.

The Si-SiO2 interface and bulk oxide degradation during both channel hot electron (CHE) and Fowler-Nordheim stress conditions and its possible causal correlation to hydrogen release at the interface and/or hot hole injection (HHI) is investigated. The results indicate that anode hole injection (AHI) is still operative at V(sub G) lower than previously experimentally demonstrated.

Research was conducted to examine the reliability of hot-carrier-induced luminescence (HCL) as a tool for verifying carrier energy distribution functions in submicron silicon devices treated to high electric fields. In this study, experimental data were compared with two-dimensional HCL simulations in silicon. Results revealed similarities between actual and simulated data as regards bias, temperature ranges and wide channel length.

Stress experiments and Monte Carlo common emitter current gain hFE degradation reveal that hot hole impact ionization and secondary electrons cause the degradation. The transistor lifetime exponentially depends on the open collector base-emitter breakdown voltage BVEBO. High temperatures, applied during reverse-bias stress, decrease the degradation effects of bipolar hFE.

We previously reported a novel photoluminescence (PL) with a distribution of fast decay times in fused silica surface flaws that is correlated with damage propensity by high fluence lasers. The source of the PL was not attributable to any known silica point defect. Due to its broad spectral and temporal features, we here give this PL the name quasi-continuum PL (QC-PL) and describe the features of QC-PL in more detail. The primary features of QC-PL include broad excitation and emission spectra, a broad distribution of PL lifetimes from 20 ps to 5 ns, continuous shifts in PL lifetime distributions with respect to emission wavelength, and a propensity to photo-bleach and photo-brighten. We found similar PL characteristics in surface flaws of other optical materials, including CaF2, DKDP, and quartz. Based on the commonality of the features in different optical materials and the proximity of QC-PL to surfaces, we suggest that these properties arise from interactions associated with high densities of defects, rather than a distribution over a large number of types of defects and is likely found in a wide variety of structures from nano-scale composites to bulk structures as well as in both broad and narrow band materials from dielectrics to semiconductors. [ABSTRACT FROM AUTHOR]

Previous studies have identified two significant precursors of laser damage on fused silica surfaces at fluences <35 J/cm²: photoactive impurities from polishing and surface fractures. We evaluate isothermal heating as a means of remediating the defect structure associated with surface fractures. Vickers indentations are applied to silica surfaces at loads between 0.5 and 10 N, creating fracture networks. The indentations are characterized before and following thermal annealing under various time and temperature conditions using confocal time-resolved photoluminescence (CTP) imaging, and R/1 damage testing with 3-ns, 355-nm laser pulses. Improvements in the damage thresholds with reductions in CTP intensity are observed at temperatures well below the glass transition temperature (Tg). The damage threshold on 0.5-N indentations improves from <8 to 35 J/cm² after annealing at approximately 750°C. Larger fracture networks require longer or higher temperature treatment to achieve similar results. At an annealing temperature 1100°C, optical microscopy indicates morphological changes in some of the fractures surrounding the indentations, although remnants of the original fractures are still observed. We demonstrate the potential of using isothermal annealing to improve the laser damage resistance of silica optics, and provide a means of further understanding the physics of optical damage and mitigation. [ABSTRACT FROM AUTHOR]

Presents a Monte Carlo simulation of the Channel Initiated Secondary Electron flash memory cell. Characteristics of flash memories; Channel hot electron programming; Understanding carrier heating in metal oxide semiconductor field effect transistors through Monte Carlo simulation.