Energy distribution, of sputtered particles

For a good understanding of SIMS spectra it is important to have at least a qualitative understanding of phenomena such as sputtering, ionization and neutralization, ion-induced electron and light emission, and the energy distribution of sputtered particles. 

The interaction of keV particles with solids has been characterized by the measurement of the angle and energy distribution of sputtered secondary ions and neutrals. The results are compared to classical dynamics calculations of the ion impact event. Examples using secondary ions are given for clean Ni 001), Cu 001) reacted with 0>, Ni 001 and Ni 7 9 11 reacted with CO, and Agllll) reacted with benzene. The neutral Rh atoms desorbed from Rh 001 are characterized by multiphoton resonance ionizaton of these atoms after they have left the surface. 

The number of atoms sputtered by a single incident ion varies with an ion s individual trajectory. Figure 15 shows the distribution of sputtered particles per incident ion at four different primary energies. As the collision energy increases from 100 to 1000 eV, the most probable yield shifts from 0 to 5 sputtered atoms per ion impact. The computer program, TRIM, mentioned earlier, provides quantitative simulations of both sputtering thresholds and yields. ... 

TOP mass spectrometers of the reflectron type are particularly suitable because they compensate, via different path lengths in an electrostatic reflector, for the time spreading caused by the energy distribution of the sputtered particles. In contrast to quadrupole or magnetic sector mass spectrometers, TOP instruments enable parallel detection of all species in a bunch of postionized sputtered particles. Repetition... 

The distribution of sputtered flux depends upon the angle at which the sputtered atom emerges from the solid, the energy of the incident particle, and the angle at which the incident particle strikes the solid. 

Figure 1 shows the energy-particle distribution of Nb atoms at the substrate for two different voltages, a constant argon sputtering pressure of 2.6 Pa (20 mTorr),... 

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