Damage buildup in Si under bombardment with MeV heavy atomic and molecular ions

Abstract

The effect of as-implanted damage on the microstructure of threading dislocations in MeV implanted silicon Bi 2 ions ͑the so-called molecular effect͒ is studied by Rutherford backscattering/channeling spectrometry. Results show that the damage buildup is sigmodal even for such heavy-ion bombardment at liquid nitrogen temperature. This strongly suggests that, for the implant conditions of this study, the buildup of lattice damage cannot be considered as an accumulation of completely disordered regions. Instead, damage-dose curves are well described by a cascade-overlap model modified to take into account a catastrophic collapse of incompletely disordered regions into an amorphous phase after damage reaches some critical level. Results also show that Bi 2 ions produce more lattice damage than Bi 1 ions implanted to the same dose. The ratio of lattice disorder produced by Bi 2 and Bi 1 ions is 1.7 near the surface, decreases with depth, and finally becomes close to unity in the bulk defect peak region. Parameters of collision cascades obtained using ballistic calculations are in good agreement with experimental data. The molecular effect is attributed to a spatial overlap of ͑relatively dense͒ collision subcascades, which gives rise to ͑i͒ nonlinear energy spike processes and/or ͑ii͒ an increase in the defect clustering efficiency with an effective increase in the density of ion-beam-generated defects.

Amorphization of crystalline Si due to heavy and light ion irradiation

“…This is in agreement with other recent experimental observations on the amorphization of silicon during molecular ion 23 and ion cluster 24 irradiations. This is in contrast to the work performed in the late 1970s/early 1980s by Thomson and co-workers ͑see, for example, Refs.…”

An in situ transmission electron microscopy study of the ion irradiation induced amorphisation of silicon by He and Xe

“…It had previously been assumed that within the confines of a collision cascade the material is always rendered amorphous thus producing spatially isolated amorphous zones [9][10][11]. Recent work on the annealing of damage created by individual collision cascades [9,12], cascade overlaps [2] and cluster/molecular ion irradiation [13,14] has indicated that this may not necessarily be true with the cascade volumes consisting of variable levels of damage ranging from dilute up to completely amorphous.…”

Atomistic simulation of damage production by atomic and molecular ion irradiation in GaN

“…However, not many works have been focused on the defect formation behaviour when irradiation is done by molecular projectiles. Some experiments have shown that the damage production itself in semiconductors is non-linear with the deposited energy density of single and molecular projectiles [12][13][14]. There are also experiments investigating the effect of ion-beam-produced defects on luminescence properties [15][16][17][18].…”