Thin-Layer Ablation of Metals and Silicon by Femtosecond Laser Pulses for Application to Surface Analysis

Abstract

For the purpose of thin-layer surface analysis, comparison of laser ablation by 24 ns ArF laser pulses at 193 nm and that by 150 fs Ti:sapphire laser pulses at 780 nm for samples ranging from metals to semiconductors is reported. In contrast to nanosecond laser pulses, the ablation threshold for femtosecond laser pulses could be reduced significantly. In particular, the threshold for a Si sample was reduced to about one order of magnitude, and an ablation rate of 0.48 nm/shot was obtained at 5% above the threshold fluence. The root-mean-square (RMS) growth rate in the roughness of the ablated surface was 0.05 nm/shot. These results show the advantages of femtosecond laser ablation for trace element analysis of a wide range of materials, coupled with laser-induced fluorescence (LIF) spectroscopy.

Laser ablation in analytical chemistry—a review

“…Preliminary research using femtosecond lasers for analytical spectroscopy has only recently been reported [28,29].…”

“…Femtosecond laser pulses might be favorable for providing reduced fractionation because of minimal thermal effect [27]. Preliminary studies using femtosecond lasers for analytical spectroscopy have been reported recently [28,29].…”

Femtosecond laser ablation elemental mass spectrometry

“…Ablation of less than 10 nm per shot has been demonstrated with fs-laser (Nolte et al, 1997;Kim et al, 2000; and that is close to depth resolutions of the best established in-depth analysis techniques, such as secondary ion mass spectrometry (SIMS) and glow discharge-mass spectrometry (GD-MS), typically 5-10 nm (Bubert & Jenett, 2001). At the same time, those techniques have different lateral resolutions, in the range from 100 nm (SIMS) to a few mm (GD-MS).…”

“…The best results of LA in-depth profiling can be expected at the ultra-high vacuum (UHV) conditions that are necessary for most of the established techniques (Schütze et al, 1995;Kim et al, 2000;Garcia et al, 2003); however, laser ablation in-depth profiling could be performed also in the presence of a noble gas or under atmospheric conditions (Anderson et al, 1995;Vadillo & Laserna, 1997;Bleiner et al, 2000;Plotnikov et al, 2001). That possibility is significant for many applications where fast, on-line analysis is needed, and therefore UHV should be avoided.…”

Improved Analytical Characterization of Solid Waste-Forms by Fundamental Development of Laser Ablation Technology

“…Based on interactions with the physics community, the PI believes that femtosecond laser pulses will provide an ideal environment for matrix independence because of the minimization of thermal effects. Preliminary research using femtosecond lasers for analytical spectroscopy has only recently been reported (48,49). Research by the physics community has demonstrated that femtosecond lasers provide a different particle size distribution that that from longer-pulsed lasers, although a comparison of the particle chemistry has not been reported.…”