Depth profiling of nanometer thin layers by pulsed micro-discharge with inductively coupled plasma mass spectrometry

A depth profile technique has been developed for ultrathin layer analysis by combining a pulsed micro-discharge device with inductively coupled plasma mass spectrometry (ICPMS). With a tungsten needle as the anode and the sample as the cathode, a local micro-plasma was formed in the 50 μm discharge gap, which contributed to the ablation of the sample. We analyzed a series of Ni coating samples with thicknesses of 5, 10, 15, and 20 nm in this study. Although the micro-discharge was shown to be an arc, pulsed mode operation provided an extra control over the power output and the discharge time that enabled precision ablation of submillimeter in lateral scale and 0.6 nm in depth per pulse. A further attempt was made to demonstrate the ability in thickness determination using the calibration curve for layers of different thicknesses. Our results show that the pulsed micro-discharge could directly ablate a solid sample under ambient conditions and that it is an effective low-cost method for depth profiling of nanometer thin layers.