engleski

EPR Study of Amorphous Silicon Produced by Ions Implatation into Silicon

Ions implantation into silicon frequently is employed to obtained thin layer of amorphous silicon. In the production of such thin films the various type of defects in the implanted layer or in the boundary between crystalline and amorphous phase are formed. Production of various types of electronic devices requires minimum concentration level of such defects and especially paramagnetic type of defects. The most often form of paramagnetic defects is a well-known dangling bond in the silicon lattice. Implantation of He, Kr, Au, Si, ions produced dominant paramagnetic defects characterized by singlet at g=2.0055 in an EPR spectrum. This singlet is often found in amorphous silicon and is attributed to neutral charge state of dangling bond in the vacancy cluster (1). The information on cluster structure of these centers can be obtained from the EPR lineshapes studies (2). On the other side, implantation H2+ and D2+ ions under the similar condition as heavier ions produce S1 type of paramagnetic defects (3) and defects with corresponding singlet at g=2.0066 which was earlier denoted as S2 defect (4). The microscopic structure of S2 defect has been studied by examining temperature dependence of EPR spectra and by subsequent annealing. The shift in the g-value only for EPR spectra produced by hydrogen ions is therefore ascribed to presence of hydrogen-related defects in the implanted layer. This complex spectrum can be decomposed into isotropic and anisotropic component. The relative concentration of anisotropic component is larger in Czochralski silicon and smaller in Float zone silicon than the respective isotropic component. The involvement of hydrogen and oxygen atoms in the center has been discussed. It is suggested that S2 center is developed in the multi-vacancy defect containing oxygen and hydrogen atoms.

EPR; paramagnetic center; silicon

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