Study on Properties of the Secondary Ions by an Ion Bombardment Mass Spectrograph

Abstract

An ion-bombardment mass spectrograph has been developed with the emphasis on high mass-resolving power of 2500, yet with simple construction. It consists of a Penning ion source for primary ion production, an electrostatic lens column(an einzel lens and a quadrupole lens)for beam focusing of the primary ion, and a CEC 21-110 B double-focusing mass spectrograph without the spark ion source for analyzer. The specimen was bombarded with the Ar+ beam of 8 keV energy, 300μ beam diameter and 1 mA/cm2 current density.A comparison of the spectra produced by the rf spark and the ion bombardment, and the influence of atmosphere in the specimen chamber on the secondary ion intensity have been studied. The ion bombardment produces various polymeric and compound ions while the rf spark produces few of these ions. The rf spark produces many more multiply charged ions than the ion bombardment It is found that the secondary ion intensites of metals increase when bombarding in oxygen pressure of larger than 3 × 10-7 Torr(ultimate pressure), and that the increasing tendency varying with different metals. The secondary ion intensities of impurity elements in a metal show the same increasing tendency with the matrix element. Especially, in case of the iron sample, the secondary ion intensities of impurity elements can be maintained at high sensitivity and stability, and the relative sensitivities approach to the sensitivity of the matrix element by bombarding in oxygen pressure of 3-5×10-5 Torr. No influence of hydrogen or nitrogen pressure in the specimen chamber on the secondary ion intensity has been observed.