Partially Damaged Research Articles

Influence of doping on ion-induced growth and shrinkage of partial damage in silicon

In this work we report the first experimental evidence that the balance between dynamic crystallization and amorphization is influenced by the presence of dopants through a detailed study on the effects produced by energetic ion beam irradiation on partially damaged, doped Si crystals. Predamaging was produced by room temperature 150 keV Au + implantations to a dose of 2 × 10 13/cm 2 onto undoped, B-doped, and P-doped 〈100〉 oriented Si single crystals. The doping species were present in the samples at concentrations in the range 1.5 × 10 20−2 × 10 21/cm 3. The low dose Au implants resulted in the formation of small damage clusters embedded in a defect-free crystal matrix. Samples were subsequently irradiated by 600 keV Kr2 + ions at different doses and at temperatures in the range 350–500 K. In the case of undoped samples a reordering of the damage clusters is observed for substrate temperatures above 420 K (critical temperature). At lower temperatures damage accumulation is observed. Doping strongly influences the balance between damage accumulation and reordering: the critical temperature becomes 390 K for P-doped samples at a concentration of ∼ 2 × 10 20 P/cm 2 and 360 K for P-doped samples at a concentration of ∼ 2 × 10 21/cm 3. This behavior is discussed and explained on the basis of a phenomenological model.

Partially damaged molecules after irradiation of dry invertase with fast electrons and protons.

Experiments with commercial yeast invertase showed that, in addition to a fraction of inactivated molecules, a fraction of heat-labile molecules was formed by irradiation with electrons or protons. The results demonstrate the possibility of partial damage due to the action of ionizing radiation on large molecules.