Application of laser ablation inductively coupled plasma quadrupole mass spectrometry (LA-ICP-QMS) for depth profile analysis

Abstract

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to perform depth profile analysis of Ti-based single layers deposited on steel and WC/Co substrates. Ablation parameters adjustable with a commercially available Nd∶YAG 266 nm laser, e.g., energy density, frequency and spot size, were optimized to obtain the best depth resolution and high reproducibility of the measured layer thickness. For comparison, a classical calotte grinding technique and glow discharge optical emission spectroscopy (GD-OES) were used. Using LA-ICP-MS, thickness determination could be performed to within 5% RSD under optimum conditions, though a strong influence of layer composition on the slopes of calibration curves was observed. For the materials investigated, an ablation rate of ≤100 nm per shot using 1.5 mJ beam energy, 120 µm spot size and 5 Hz was obtained. A depth resolution of ≤2.5 µm was determined by the measured intensity–time profiles of the investigated isotopes.