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Prospect of increasing secondary ion yields in ToF‐SIMS using water cluster primary ion beams
Author(s) -
Sheraz née Rabbani S.,
Barber A.,
Berrueta Razo I.,
Fletcher J. S.,
Lockyer N.P.,
Vickerman J. C.
Publication year - 2014
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.5606
Subject(s) - ion , chemistry , ionization , cluster (spacecraft) , analytical chemistry (journal) , ion source , proton , secondary ion mass spectrometry , atomic physics , nuclear physics , physics , chromatography , organic chemistry , computer science , programming language
Low ionization yields in time of flight secondary ion mass spectrometry (ToF‐SIMS) particularly from single cells and tissues are proving to be a significant limitation in allowing this technique to reach its full potential. A number of approaches including embedding the sample in water or spraying water above sample surface has shown great prospective for increasing the ionization yield by a factor of 10 to 100 through ‘proton mediated’ reaction. Based on this hypothesis, a water cluster primary ion source has been developed in collaboration with Ionoptika Ltd to generate giant water cluster ions (H 2 O) n + ( n = 1−10 000) using a similar supersonic jet expansion methodology as for argon cluster beams. The ion yields of arginine, cholesterol, angiotensin II and a lipid mix have been measured under static and high ion dose conditions using (H 2 O) 5000 + , (H 2 O) 3000 + , Ar 3000 + and C 60 + primary ion beams at 20 keV. An enhancement in yields up to a factor of around 4 is observed under water cluster impact, in comparison with C 60 + at 1 × 10 11 ions/cm 2 ion dose, whereas this increases by around 10–50 times at high ion dose conditions. Copyright © 2014 John Wiley & Sons, Ltd.