Buffer-gas assisted high irradiance femtosecond laser ionization orthogonal time-of-flight mass spectrometry for rapid depth profiling

High irradiance femtosecond laser ionization orthogonal time-of-flight mass spectrometry (fs-LI-O-TOFMS) has been applied for the depth profile analysis of multilayer samples. Elements in each layer can be determined with respect to the depth of solid sample surfaces. A nanosecond laser was also applied in parallel for comparison. The analytical performances as well as crater formation mechanisms of femtosecond and nanosecond laser ablation and ionization were compared. Superiorities of the depth resolution and trace elemental detection were observed in the femtosecond laser mode. fs-LI-O-TOFMS is capable of presenting the complete and explicit spectrum for each laser shot, performing depth profiling of coated layers with various thicknesses (tens of nanometers to tens of micrometers), providing multi-elemental information, and examining samples with conductive and nonconductive substrates. High irradiance femtosecond laser ionization orthogonal time-of-flight mass spectrometry is capable of providing abundant useful information for depth profiling.