In-situ ion beam irradiation: X-ray scattering & diffraction experiments


In-situ ion beam irradiation: X-ray scattering & diffraction experiments

Roshchupkina, O. D.; Baehtz, C.; Facsko, S.; Bischoff, L.; Posselt, M.; Grenzer, J.

Ion beam techniques are widely used in semiconductor and thin film industry for introducing dopant atoms into materials. Ion implantation is characterized by fast dynamic processes related to the formation and relaxation of collision cascades (100fs – 100ps), finally leading to the formation of different types of defects (vacancies, self-interstitials, clusters, etc.). The material undergoes also other strong modifications. For instance, implantation leads to a strained layer which expands in the direction normal to the substrate surface. This is due to the point that the bulk material prevents any lateral macroscopic expansion; and as a result the thin irradiated layer is subjected to an in-plane biaxial compressive stress due to the continuous accumulation of defects. Unfortunately, ion irradiation is a very fast process and it is almost impossible to monitor it in-situ with the present x-ray sources. However, the accumulation of damage and the diffusion of defects and implanted species are much slower process and can be observed in-situ using a time resolution in the order of seconds.
An in-situ ion beam implantation experiment was set up at ROBL/MRH at ESRF. For this purpose an ion gas source with a maximal acceleration voltage of 5keV was mounted on a sputtering chamber. To realize sufficient volume damage the ion energy was further raised by increasing the electrostatic potential of the irradiated sample to 20keV using an additional power supply. Si and Al2O3 (001)-oriented substrates were irradiated using He+ at an ion flux of about 10^{13}ions/cm^{2}s at room temperature. Reciprocal space maps were measured to study the evolution of the implanted layer.

Keywords: In-situ ion beam implantation

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