It was recalled that the interstitial ion, Cui+, was a fast-diffusing impurity. The isolated interstitial was a shallow donor, but it reacted with impurities and defects and these reactions affected the electrical properties of the material. The Cu passivated shallow acceptors, formed pairs with various impurities (including itself) and precipitated at defects. Some of the latter precipitates were strong electron-hole recombination centres. Interstitial and substitutional Cu, Cu-acceptor pairs, and Cu precipitation at the ring hexavacancy, were studied here. The chemistry of Cu was not as simple as was commonly supposed; even in the case of Cui+. The interstitial ion was not in the 3d104sp0 configuration as was often assumed, but transferred some electrons into the 4sp shell. This was then responsible for the various covalent interactions between Cu and the host crystal.

Rich Chemistry of Copper in Crystalline Silicon S.K.Estreicher: Physical Review B, 1999, 60[8], 5375-82