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

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 less than or equal to 100 nm per shot using 1.5 mJ beam energy, 120 mum spot size and 5 Hz was obtained. A depth resolution of less than or equal to2.5 mum was determined by the measured intensity-time profiles of the investigated isotopes.