Yields Of Cluster Ions Research Articles

Secondary Ion Emission from Si Subjected to Oxygen Ion Bombardment

The secondary ion yields and energy distribution of positive ion species sputtered from an Si surface under O+2 ion bombardment were measured using UHV-SIMS. The SIMS spectra obtained contained peaks due to the following cluster ion species; Si+, SiO+, Si+2, Si2O+, SiO+2, Si2O+2 and Si2O+3. The secondary ion yield was found to exhibit a depend on the primary ion energy. The secondary Si ion yield increased gradually with increasing energy, but the secondary cluster ion yield first increased and then decreased gradually through a maximum at an energy of 10∼15 keV. The most probable energies of cluster ions such as Si2O+ and Si2O+3 were also found to vary with the primary ion energy. The FWHM values in the energy distributions decreased linearly with increase in the mass of the sputter ion species, while the tail factor decreased with the mass of the cluster ions.

Particle ejection from ion-bombarded clean and reacted single-crystal surfaces

A model based on a classical dynamical calculation of the impact of a 600-eV Ar+ ion into a single crystal has been developed to the point where it compares quantitatively to a wide variety of experimental observables. Here, we make direct comparisons between experiment and theory for relative sputtering yields, energy and angular distributions of the ejected atoms, and multimer yields. The model is also extended from clean single-crystal surfaces to include adsorbate atoms and molecules. These results are compared to experimental SIMS studies aimed at sorting out the structure-sensitive factors that contribute to the cluster ion yield. In oxygen chemisorption on Ni(100), for example, the O2−/O− yield is four times larger for a c (2×2) coverage than for a p (2×2) coverage, a value also predicted by the calculations. In molecular CO chemisorption, the ejection of CO is found to occur molecularly in both the experiments and in the calculations. In comparison to the calculations, a high value of Ni2CO+/NiCO+ is consistent with a bridge-bonded CO structure at low coverage.

A study of the interaction of oxygen with chromium using ion bombardment induced photon and secondary ion emission

Oxygen ion bombardment, or ion bombardment in an oxygen atmosphere is often used to enhance the ion yield from metallic targets, when secondary ion mass spectrometric analysis is being attempted. However, there exist few detailed studies of the effect of oxygen environment on the yields of various ions emitted from an ion bombarded surface. In this work we report detailed observations of the effect of a varying oxygen background pressure on the yield of ions of the form Cr + n and Cr m O + n from a polycrystalline Cr target. Observations of the variation of the photon yield from the same target, as the oxygen background pressure is changed are also reported. From these observations some conclusions regarding the effect of oxygen absorption on cluster ion yields and on the mechanisms of ion emission can be deduced. In particular it is shown that blocking of electronic transitions as a result of oxygen adsorption cannot account for the total variation of Cr + emission with increasing oxygen pressure.