Effect of impurities on the growth of {113} interstitial clusters in silicon under electron irradiation

Abstract

The growth and shrinkage of interstitial clusters on {113} planes were investigated in electron irradiated Cz-Si, Fz-Si, and impurity-doped Fz-Si (HT-Fz-Si) using a high voltage electron microscope. In Fz-Si, {113} interstitial clusters were formed only near the beam incident surface after a long incubation period, and shrank on subsequent irradiation from the backside of the specimen. In Cz-Si and HT-Fz-Si, {113} interstitial clusters nucleated uniformly throughout the specimen without incubation, and began to shrink under prolonged irradiation at higher electron beam intensity. At lower beam intensity, however, the {113} interstitial cluster grew stably. These results demonstrate that the {113} interstitial cluster cannot grow without a continuous supply of impurities during electron irradiation. Detailed kinetics of {113} interstitial cluster growth and shrinkage in silicon, including the effects of impurities, are proposed. Then, experimental results are analyzed using rate equations based on these kinetics.

2 MeV e‐irradiation UHVEM study on the impact of O and Ge doping on {113}‐defect formation in Si

“…With increasing specimen thickness, the interstitial concentration goes through a maximum leading also to a maximum in {113}‐defect nucleation and growth. For further increasing specimen thickness (see the simulations for the 500, 1000 and 2000 nm specimen thickness), the bulk of the sample becomes vacancy‐rich and {113}‐defect formation is limited to the near surface areas with a thin denuded zone adjacent to the surface as also observed experimentally 10, 23. The peak concentration of interstitials also goes down, leading to slower defect formation.…”

“…By comparing the nucleation and growth of {113}‐defects in floating zone Si during in situ irradiation in an ultra high vacuum transmission electron microscope with (pressure in the specimen chamber kept at 5 × 10 −5 Pa) and without (10 −7 Pa) oxygen injection in the specimen chamber, Koto et al 22 showed that an increasing amount of oxygen in specimen chamber vacuum enhances defect formation. Also in a recent 1 MeV in situ e‐irradiation study, it was concluded that also impurities that are introduced at the specimen surface play an important role in the nucleation of {113}‐defects 23. This shows that one should use the cleanest possible e‐beam and vacuum to avoid uncontrolled introduction of impurities in the Si specimen during irradiation.…”

Athermal Crystal Defect Dynamics in Si Revealed by Cryo-High-Voltage Electron Microscopy

“…It is presumed that the disappearance of the defects under 1 MeV electron irradiation is due to migration of interstitial atoms to an equivalent plane, which does not satisfy the edge-on condition, or annihilation at the specimen surface. Shrinkage of the defects can also be explained by the purification of the irradiated area by the absorption of pre-existing impurities into interstitial clusters . Since {113} defects are not formed in a thin region near the specimen edge, observation in a thick region is essential for such defect dynamics characterization.…”

“…Shrinkage of the defects can also be explained by the purification of the irradiated area by the absorption of pre-existing impurities into interstitial clusters. 27 Since {113} defects are not formed in a thin region near the specimen edge, 16 observation in a thick region is essential for such defect dynamics characterization. The veiled phenomenon was hence detected by the experiment simultaneously satisfying the following three conditions using a sufficiently thick specimen: low temperatures (<100 K), highenergy electron irradiation (1 MeV), and atomic resolution.…”