Journal of Chromatography & Separation Techniques
Open Access
ISSN: 2157-7064
+44 1300 500008
ISSN: 2157-7064
+44 1300 500008
Purushottam Chakraborty
Saha Institute of Nuclear Physics, India
Keynote: J Chromatogr Sep Tech
Excellent detection sensitivity, high dynamic range and good depth resolution make the secondary ion mass spectrometry
(SIMS) extremely powerful for the analysis of surfaces and interfaces of low-dimensional materials. Our focus is the
controlled growth, characterizations and modifications of low-dimensional structures with tunable morphology and
properties. However, a serious problem in SIMS is its â??â??matrix effectâ??â?? that hinders the materials quantification. Realistic SIMS
quantification having analytical accuracy better than ?±20% requires the analysis of standard samples of the impurity species
in the chemical matrix of interest. These standards are necessary because secondary ion-yields depend on the instantaneous
surface chemistry of the sample. This ion-yield variation, known as â??matrix effectâ? is a function of the electronic and vibrational
states of both the sputtered species and the surface as well as the chemical bonding of the species to the surface. Ion-yields
in SIMS can vary by several orders of magnitude, thus effectively preventing quantitative SIMS analysis. Corrective measures
are therefore needed to calibrate the secondary ion currents into respective atomic concentrations for accurate compositional
analysis. Working in the MCs+-SIMS mode (M-element to be analyzed and Cs+-bombarding ions) can circumvent the matrix
effect. The emission process for the 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) as
the yields of such molecular ion complexes have often been found to be higher than that of MCs+ ions. Several works have been
reported on the emission of MCsn+ molecular ions, but a complete understanding on the formation mechanisms of these ion
complexes is still lacking. The MCsn+-SIMS technique in all its complexities has great relevance in the analysis of materials. A
procedure for the accurate quantification of Ge concentration in MBE-grown Si1â??xGex (0 Purushottam Chakraborty was a Senior Professor of Saha Institute of Nuclear Physics, India till 2015 and is currently a Visiting Professor of Physics at Sultan Qaboos University, Muscat, Sultanate of Oman. He has completed his PhD from Calcutta University and did his Post-doctoral research at FOM-Institute for Atomic and Molecular Physics in Netherlands, Padova University in Italy and Laval University in Canada. He was associated with the Osaka Electro-Communications University, Japan, University of Pretoria, South Africa and Friedrich Schiller University, Germany as a Visiting Professor of Physics. He has authored more than 150 scientific papers including book-chapters and review articles. He was awarded the most Eminent Mass Spectrometrist of India in 2003. Biography :