Analysis of high purity solids by resonance ionization spectroscopy

Resonance Ionization Spectroscopy (RIS) techniques provide ultrasensitive methods for analysis of materials. One of these techniques, Sputter Inititated Resonance Ionization Spectroscopy (SIRIS), uses an energetic ion beam to atomize a solid sample and tunable dye lasers to resonantly ionize atoms of a selected element. The ions are then detected with a mass spectrometer. Because of the high selectivity and efficiency of the RIS process, SIRIS is a highly sensitive technique and can be used to detect trace elements down to the ppb level. While SIRIS is primarily a surface technique, depth profiles can be produced by iteratively sputtering with the beam in the dc mode and then measuring the sample with resonance ionization using the pulsed ion beam. For example, the depth profiles of silicon implanted into gallium arsenide and titanium diffused into lithium niobate have been measured. The concept of RIS is briefly reviewed and the SIRIS technique and apparatus are described. Results of measurements in silicon, gallium arsenide, and lithium niobate are discussed along with other supporting data.