This theoretical–experimental study focuses on the formation of the substitutional-tri-interstitial cluster Cus1Cui3, which has been proposed as the photoluminescence defect CuPL. The configurations and electronic properties of the intermediate defects Cus1Cui1 and Cus1Cui2 are calculated, and their electrically active levels are obtained from conventional and Laplace deep-level transient spectroscopy. The vacancy formation energy near copper-related defects is calculated and found to be much smaller than in the perfect crystal. Then, we show how Cus1Cui3 could become the seed of agglomerates of Cus1Cui3 “units.” The discussion focuses mostly on unanswered questions about the discrepancies between the calculated and measured properties of CuPL and Cus1Cui3.

Electronic devices generate unwanted heat. The removal of this heat often involves a layer of a high‐thermal‐conductivity material X deposited at a strategic location on the Si chip. The layer is then cooled using a mechanical fan or more sophisticated means. The authors present here the results of ab‐initio molecular‐dynamics simulations which examine the thermal interactions between heat generated in Si and three materials X: Ge, C, and Si itself. The geometry is a very thin wire of atoms X located within a Si slab. Heat is periodically removed from the wire as if it were connected to a heat sink. The wire then absorbs heat from the warmer Si slab, thus cooling it. The rate at which the Si temperature drops depends on how efficiently heat crosses the Si|X boundary and then is absorbed by the wire. The interactions involve the coupling of Si‐Si vibrational modes with Si‐X (interface) and then X‐X (layer) modes. The worst performance occurs for XC as lower‐frequency Si‐Si modes must decay into higher‐frequency Si‐C then CC modes. This involves slow two‐ (or more) phonon processes. The fastest cooling rate occurs when the wire is made of Si itself: there is no Si|Si interface and the vibrational interactions involve only Si bulk modes which couple to each other resonantly. The Ge wire performs quite well, as the Si‐Si modes easily decay into lower‐frequency Si‐Ge and Ge‐Ge modes.

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 and the *Cu0 photoluminescence defect has been shown to contain one Ag atom. In this study, we predict the properties of isolated interstitial (Agi) and substitutional (Ags) silver. The calculated migration barrier of Agi is 0.53 eV, less than half the value extracted from the high-temperature solubility data. Agi has a donor level high in the gap and is in the positive charge state for most positions of the Fermi level. When interacting with a pre-existing vacancy, Agi becomes Ags with a gain in energy slightly higher than in the case of Cu but still less than the formation energy of the vacancy calculated at the same level of theory. The calculated donor and acceptor levels of Ags are close to the measured ones, and we predict a double-acceptor level that matches a Ag-related (but otherwise unidentified) level reported in the literature. The AgsCui pair is more stable than the CusAgi pair. Ags can trap several Cuis and form Ags1Cuin complexes (n = 1–4) that are similar to the Cus1Cuin ones. When needed, their calculated binding energies are corrected to account for a change of the charge state following the formation of the complex. This correction is Fermi level dependent. We tentatively assign the *Cu0 defect to Ags1Cui3 even though the single-donor level associated with *Cu0 does not match the calculated one.