TY - JOUR KW - Model KW - Particle KW - Particles KW - Lead KW - Transformation KW - USA KW - Surface KW - Power KW - Films KW - Ablation KW - Laser KW - Laser ablation KW - Laser ablation KW - Time-resolved KW - State KW - Time KW - Ca KW - E KW - Liquid KW - Sample KW - C KW - Crater KW - Volume KW - Nanosecond KW - Metal KW - Nanosecond laser KW - Depth KW - Silicon KW - Layer KW - Threshold KW - Generation KW - Particulates KW - Irradiance KW - Circulation KW - Phase explosion KW - Phase-explosion KW - Physics KW - Single-crystal KW - Dielectric KW - Thickness KW - Transparency KW - Critical state KW - Critical-state KW - Deep KW - Ejection AU - Jong-Hyun Yoo AU - Sungho Jeong AU - Xianglei Mao AU - Ralph Greif AU - Richard E Russo AB -

The craters resulting from high-irradiance (1×109–1×1011 W/cm2) single-pulse laser ablation of single-crystal silicon show a dramatic increase in volume at a threshold irradiance of 2.2×1010 W/cm2. Time-resolved shadowgraph images show ejection of large particulates from the sample above this threshold irradiance, with a time delay ∼300 ns. A numerical model was used to estimate the thickness of a superheated layer near the critical state. Considering the transformation of liquid metal into liquid dielectric near the critical state (i.e., induced transparency), the calculated thickness of the superheated layer at a delay time of 200–300 ns agreed with the measured crater depths. This agreement suggests that induced transparency promotes the formation of a deep superheated layer, and explosive boiling within this layer leads to particulate ejection from the sample.

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Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA Kwangju Inst Sci & Technol, Kwangju 500712, South Korea

BT - Applied Physics Letters C2 - LBNL-44782 DA - 02/2000 DO - 10.1063/1.125894 IS - 6 LA - eng LB - Laser N1 -

LBNL-44782 NOT IN FILE

N2 -

The craters resulting from high-irradiance (1×109–1×1011 W/cm2) single-pulse laser ablation of single-crystal silicon show a dramatic increase in volume at a threshold irradiance of 2.2×1010 W/cm2. Time-resolved shadowgraph images show ejection of large particulates from the sample above this threshold irradiance, with a time delay ∼300 ns. A numerical model was used to estimate the thickness of a superheated layer near the critical state. Considering the transformation of liquid metal into liquid dielectric near the critical state (i.e., induced transparency), the calculated thickness of the superheated layer at a delay time of 200–300 ns agreed with the measured crater depths. This agreement suggests that induced transparency promotes the formation of a deep superheated layer, and explosive boiling within this layer leads to particulate ejection from the sample.

PY - 2000 SP - 783 EP - 785 ST - Appl. Phys. Lett. T2 - Applied Physics Letters TI - Evidence for phase-explosion and generation of large particles during high power nanosecond laser ablation of silicon VL - 76 ER -