Charging of insulators by ion bombardment and its minimization for secondary ion mass spectrometry (SIMS) measurements

Abstract

The generation of charge build-up, caused by bombardment of insulating samples with energetic particles, and its role in altering the relative secondary-ion currents and reducing their absolute values, sometimes even to zero, are discussed. Proposed methods for charge reduction by bombardment with negative ions or with neutral particles, or by use of an auxiliary electron beam or spray gun, are shown to be not useful in every experimental situation. A further method involving introduction of an auxiliary conducting electrode when using negative primary ions is considered mechanistically, and tested by placing tantalum diaphragms onto the surface of yttrium iron garnet (YIG). The final charging values and mass spectra thus obtained are compared to those measured when using bare and metallic grid-covered surfaces of the same YIG sample. The satisfactory results achieved with the diaphragm show that SIMS analyses of insulators can be performed in a simple, quick, and inexpensive manner.

Primer on Agar-Based Microbial Imaging Mass Spectrometry

“…The challenges in data interpretation for microbial IMS are common to all MALDI-TOF-based IMS. Black holes or areas of no signal may be due to nonuniform matrix coverage or ion suppression, whereas false gradients or signals of regular increasing or decreasing intensities may be due to decreased conductivity, charge buildup or charging (25,66), or a combination of factors (Fig. 3).…”

TOF‐SIMS characterization of an aluminovanadate oxide catalyst

“…17 To minimize charging of the sample, we employed a gold-plated molybdenum grid with a transparency of 67%, which was impressed into the sediment sample and fixed to the sample holder. The utilization of the mesh enabled acquisition of spectra without losing intensity of the peaks ( Fig.…”

SIMS–RBS depth profiling of silver‐diffused glass systems

“…The sample surface is sputtered by a 14. 5 keV Cs' beam incident on a 100 x 100 pm' region, with an ion beam current of the order of 100 nA. Secondary negative ions sputtered from the glass surface are then revealed.…”

“…In order to prevent sample charging, the sample surface is bombarded with an electron beam for compensating the charge loss due to the emission of secondary electrons and negative ions. 5 The correct surface concentration value, and the conversion constants for the secondary ion yield and for the sputtering time, are calculated by simulating an RBS experimental spectrum, obtained with a 2.2 MeV 4He+ beam. Backscattered ions are revealed at an angle of 170" using a solid-state detector with an energy resolution of 15 keV.…”