Page 170 - Inorganic Mass Spectrometry - Fundamentals and Applications

160 Cristy

1 Essential elements of secondary ion mass spectrometry.

193
nomena were slow in coming. In 1 Woodcock published the first spectra of neg-
by
ative secondary ions produced bombarding NaF and CaF, with 500 eV Li+ ions
[5]. Sloane and Press [6,7] andhot and Beckett [S] in the late 1930s studied neg-
ative ion formation resulting from ion bombardment metal surfaces. Sloane and
of
Press designed a mass spectrograph that accelerated positive ions through a mag-
netic field onto a target. Negative ions from the target were accelerated back
through the same magnetic field to a Faraday cage detector.
In 1949 Herzog and Viehbock reported a novel “ion source for mass spec-
trography” (Fig. 4.2) [9]. This source provided separate accelerating fields for the
the
primary and secondary ions and thus became first modern instrument designed
specifically for SIMS. The design included acceleration of the positive secondary
ions from an equipotential surface through an electric field acting as an electron-
optic lens.
Increasing interest in SIMS was evident in the late 1950s with publications
by Veksler and Ben’iaminovich [lo], Honig Ell], Bradley [lz], and Stanton [13].
In the early 1960s the technique was further boosted by new developments in in-
s~mentation leading to the first commercial instrument (Geophysics corporation
of America), based on designs by Liebl and Herzog [ 141. This ins~ment 151 used
[
a high brightness source, the duoplasmatron-based on a design by V. Ardenne
[ 161-and produced a small primary beam spot, -300 pm diameter. The develop-
ers demonstrated the high sensitivity of SIMS by dete~inin~ limits of detection
for a number of elements. This was also the first observation that ion yields vary
greatly from element to element [ 1 5,171.