Advanced Materials

Biography

Biography: Divya Gupta

Abstract

This paper reports on the transition of Si substitutional to interstitials under oblique argon beam irradiation. Crystalline Si (111) wafers were irradiated with 80 keV Ar+ ions to doses of 1x1017,  3x1017 and 5x1017 Ar+ cm-2  at an oblique incidence of 500 with respect to surface normal. Investigation of the defect evolution in irradiated specimens has been studied as a function of ion dose using Rutherford backscattering spectroscopy in channeling geometry and computed using the simulation code DICADA. Results demonstrate that thickness of amorphous layer increases as a function of ion dose. RBS measurements show distinctly different defect sites; for ion dose of 1x1017 Ar+cm-2, 43% of the irradiated argon ions are on Si substitutional lattice sites; clearly indicating substitution of Ar ions into lattice sites whereas for irradiation dose of 5x1017 Ar+cm-2, all the argon ions are displaced to interstitial sites; no substitution of Ar ions into lattice sites. Retained concentration has been found to be same (0.68x1017 Ar+cm-2) for all the three irradiation doses, indicating a dramatic loss of argon ions for higher fluences. This evidently indicates that defects and lattice disorder both increase as a function of irradiation dose while retained argon concentration remains independent of irradiation dose. Measurements showed that the oblique incidence resulted in depth shift of amorphous layer and enhanced surface disorder by producing substitutional and interstitial defects in the irradiated specimens. Explicitly, the ion beam induced defect transition in Si can be understood in terms of oblique incidence induced sputtering process dominated by nuclear energy loss. Such low energy oblique irradiation induced alterations in Si is of crucial importance due to its promising applications in optoelectronic domain and heteroepitaxial growth technique.