Line-focused laser ablation for depth-profiling analysis of coated and layered materials.

The performance features of line-focused laser ablation for the characterization of interfaces in layered materials by laser-induced plasma spectrometry (LIPS) have been compared with the point-focusing method in terms of signal precision, signal-to-noise ratio, ablation rates, and surface sensitivity. In both optical configurations a pulsed Nd:YAG laser beam operating at 532 nm, with a homogeneous energy distribution (flattop laser), is used to generate point and microline plasmas on the sample surface. Subsequent light from the plasma is spectrally resolved and detected with an imaging spectrograph and an intensified charge-coupled-device detector that is binned along the slit-height direction. Line-focusing LIPS permits much higher laser power input while maintaining relatively low laser fluence, thus yielding better surface sensitivity and improved detection power. Values of the signal-to-noise ratio are improved by a factor of 6. In addition the ablation rate is 9 nm/pulse with the microline approach compared with 23 nm/pulse obtained with the point-focusing method. The results demonstrate that the microline-focusing approach is suitable for the depth analysis of coated and layered materials.