Radiation Damage in Metals
I. M. Robertson
U.S. Department of Energy, DE-FG02-96ER45439
(In cooperation with the Materials Research Laboratory)

The focus of this program is to provide an understanding of the basic processes of damage formation by heavy-ion irradiation of metal systems. Transmission electron microscopy is used extensively to characterize the damage structure as a function of ion dose and irradiation temperature. The experimental information obtained is used to evaluate current damage models and to provide a better understanding of how material properties are affected in a nuclear reactor and how irradiation with energetic heavy-ions modifies the surface properties of a material.

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Amorphization and Intermixing Mechanisms in III-V Semiconductor Heterostructure Systems

Fundamental aspects of ion-beam-induced amorphization and layer intermixing in III-V semiconductor heterostructures are being studied by using a combination of low-temperature ion channeling and transmission electron microscopy techniques. Specifically, we are interested in understanding the effect of increasing the Al content on the ion dose needed to cause amorphization in the AlGaAs system and the mechanisms of mixing in AlGaAs-GaAs heterostructures.

Ion implantation is used extensively in the semiconductor industry to introduce dopants. The accompanying damage must be removed before devices can be activated. The focus of this effort is on understanding the mechanisms of solid-phase epitaxial crystallization of amorphous material in simple and compound semiconductors. The regrowth process can be stimulated by means of an energetic electron beam, which allows, through variation of the electron energy, the role of defects created in the crystalline material (interstitials and vacancies) or interface defects (dangling bonds or charged kinks) to be directly assessed.