Measurements of the secondary ion mass spectrometry isotope effect

Journal Article · Fri May 01 00:00:00 EDT 1987 · J. Vac. Sci. Technol., A; (United States)

DOI:https://doi.org/10.1116/1.574151· OSTI ID:6897771

Schwarz, S A

The heavier isotopes of a given element are generally underrepresented in the secondary ion mass spectrometry mass spectrum since they emerge from the sample with lower average velocity and are therefore less likely to be emitted as ions. The relative deviation of an isotope ratio measurement from its expected value is represented in the literature by the parameter ..cap alpha... In this work we report measurements of ..cap alpha.. as a function of secondary ion energy in high-purity Ge, Mo, Pd, Cd, Sn, and W samples; each of which offers several abundant isotopes for examination. A Cameca IMS-3f magnetic sector instrument is operated in the high-energy resolution mode for these measurements. The ..cap alpha.. values are determined from weighted least-squares fits to the isotope ratio deviations. Appropriate precautions against beam instability, mass interference, and detector saturation effects are employed. Positive and negative ion emission, induced by O/sup +//sub 2/ and Cs/sup +/ bombardment, respectively, are examined. For monatomic positive ion (M/sup +/) emission, the magnitude of ..cap alpha.. correlates roughly with the secondary ion yields and generally increases with increasing emission energy. In contrast, ..cap alpha.. values for oxide species (MO/sup +/) display an inverse dependence on energy indicating surface emission. For negative ion (M/sup -/) emission, ..cap alpha.. changes sign at low energies indicating that, at low energy, ion emission is dominated by the survival probability of the negative ion while, at higher energies, emission depends on the probability of ion formation by electron attachment. Measured ..cap alpha.. values for diatomic (M/sup +//sub 2/, M/sup -//sub 2/) emission are examined with respect to current models of molecular ion formation.

• Research Organization: Bell Communications Research, Inc., Red Bank, New Jersey 07701-7020
• OSTI ID: 6897771
• Journal Information: J. Vac. Sci. Technol., A; (United States), Vol. 5:3
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CADMIUM
ION COLLISIONS
MASS SPECTROSCOPY
CESIUM IONS
COLLISIONS
GERMANIUM
ISOTOPE EFFECTS
MOLYBDENUM
OXYGEN IONS
PALLADIUM
TIN
TUNGSTEN
ION EMISSION
MOLECULAR IONS
CHARGED PARTICLES
ELEMENTS
IONS
METALS
PLATINUM METALS
SPECTROSCOPY
TRANSITION ELEMENTS
656003* - Condensed Matter Physics- Interactions between Beams & Condensed Matter- (1987-)