Cu and Ag in Si: the elusive Cu0 and *Cu0 defects

Date

2021-08

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Abstract

Noble metals are often used for contacts on Si. A considerable amount of research has been done on Cu- and Au-related defects, but much less is known about Ag. Silver is a common contaminant in metallic copper. In this thesis, I focus on the Cu0 (also known as CuPL) photoluminescence defect which contains solely Cu, and the *Cu0 photoluminescence defect which has been shown to contain one Ag atom. In this study, I calculate the configurations and electronic properties of the intermediate defects leading to Cu0 and propose the complex Cus1Cui3 as Cu0. I also show that the calculated binding energies must be corrected to account for a change of charge state following the formation of the complex. This correction is Fermi-level dependent. The properties of isolated interstitial (Agi) and substitutional (Ags) silver are calculated here for the first time. I also show that the energetically-preferred configuration for the {Cu,Ag} pair involves substitutional Ag and interstitial Cu. I calculate the configurations and electronic properties of the intermediate defects leading to *Cu0 and propose that Ags1Cui3 is *Cu0. Finally, I study how Cu0 or *Cu0 could be the seeds of larger Cu precipitates in intrinsic Si. I first show that the vacancy formation energy near copper-related defects is much smaller than in the perfect crystal, and then show that this new process could generate aggregates of Cus1Cui3 building blocks.

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Keywords

Silicon, Copper, Silver, Semiconductor

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