Copper interactions with H, O, and the self-interstitial in silicon

The interactions between substitutional copper in Si and one to four hydrogen interstitials are studied using first-principles molecular-dynamics simulations. Up to three H's can bind covalently to one Cu_s. These complexes have been observed by deep level transient spectroscopy. The structures and binding energies are calculated, and the vibrational modes predicted. Although {Cu_s,H₄} does have a small binding energy relative to {Cu_s,H₃}+H_BC, constant-temperature dynamics show that this complex is not stable. It can break up in several ways, one of them is the dissociation into Cu_s + 2H₂ molecules. The interactions between interstitial copper and interstitial oxygen show that Cu_i⁺ prefers to be in the slightly larger void adjacent to O_i, but the binding energy is quite small (0.31 eV) and no covalent Cu-O overlap occurs. The interactions of Cu _i with an A center (oxygen-vacancy complex) involve a kickout Cu _i+{O,V}→{Cu_s,O_i}+1.7 eV, with O _i bridging a Si-Si bond immediately adjacent to Cu, which itself is at a slightly perturbed substitutional site. Again, no covalent Cu-O bonding occurs. Finally, Cu_i interacts with the self-interstitial by pushing it and one host atom away from a perfect substitutional site and moving itself toward it, at a gain of 1.6 eV.