Current Trends in Mass Spectrometry

Biography

Biography: Purushottam Chakraborty

Abstract

Excellent detection sensitivity, high dynamic range and superior depth resolution make the SIMS technique extremely powerful for the analysis of low-dimensional structures. However, a serious problem in SIMS analysis lies in its ‘‘matrix effect’’ that hinders the materials quantification. Appropriate corrective measures are therefore, needed to calibrate the secondary ion currents into respective concentrations for accurate compositional analysis. Working in the MCs+-SIMS mode (M – element to be analyzed, Cs+ – bombarding ions) can circumvent the matrix effect. The emission process for the neutral species M0 is decoupled from the MCs+ ion formation process, in analogy with the ion formation in secondary neutral mass spectrometry (SNMS), resulting in a drastic decrease in matrix effect in the MCs+-SIMS mode. Although this technique has found its applicability in direct quantification, it generally suffers from a low useful yield. In such cases, detection of MCsn+ (n = 2,3,. . .) molecular ions offers a better sensitivity, even by several orders of magnitude. A complete understanding on the formation mechanisms of these MCsn+ (n = 2,3,. . .) molecular ion complexes formed in the SIMS process has been explored. We have demonstrated the prospective use of this innovative MCsn+-SIMS technique in direct interfacial analysis of ultra-thin films, metallic multilayers, semiconductor superlattices, quantum well structures and compositional analysis of MBE grown Si1-xGex alloys without ‘standards’. The talk will address on the fundamentals, challenges and applications of the novel MCsn+-SIMS technique in all its complexities.