Secondary-ion emission from HEN semiconductive materials under MeV-energy heavy-ion bombardment

Secondary-ion emission from III-V semiconductive chemical compounds (InP, InAs, and InSb) has been experimentally studied at heavy-ion energies from 0.5 to 5.0 MeV, where electronic collision is a dominant process. Various secondary ions such as large cluster ions and atomic ions were observed. Yields of In atomic and cluster ions depend scantly on the incident energy, and those of group-V atomic ions and of cluster ions containing group-V elements can be expressed by an exponential function of S e 1, where S, is the electronic stopping power. This fact shows that the ionization probabilities of the atoms and the clusters whose ionization potentials are higher than the work functions of target materials are increased by transient electronic excitation induced by ion bombardment. The energy distributions of the atomic ions show that the singly charged atomic ions are emitted through the linear collision cascade process even at MeV incident energies, and the multiply charged ions are produced by a projectile-induced simultaneous process of ionization and recoiling of atoms on the target surface. The yield dependences of the cluster ions on the electronic stopping power and on the cluster size are so much different from those for SiO2. This fact precludes the multiple-bond-breaking process applied to the insulating material. Structural instabilities caused by high-density electronic excitations, which are known to take place in GaAs irradiated by slow multiply charged ions or lasers, are a possible cause of the cluster-ion emission from the semiconductive compounds at the MeV energy range.