Formation of an extended defect cluster in cuprous oxide

Abstract

Intrinsic defects and defect clusters play an important role in the room-temperature transport of cuprous oxide. Neutralization of these defects by doping and/or modifying the synthesis process is essential to improve the room-temperature hole mobility in cuprous oxide. Toward this end, we annealed polycrystalline cuprous oxide under Cu-rich conditions, which led to the neutralization of the intrinsic acceptor defect. The concentration of both the acceptor defects ( VCu and VCusplit ) that are already present, reduces by four to five orders of magnitude. This is in accordance with the amount of possible Cu incorporation under different annealing conditions, indicating the backfilling of a large fraction of the Cu vacancies. Unforeseeably, the experimental conditions lead to the creation of yet another higher-order extended defect (3 VCu + 2Cu i ) with a defect level at ≈0.5 eV above the valence band. The formation of such a defect is also indirectly suggested by the analysis of carrier concentration vs. temperature data and first-principles calculations. Such singly ionized higher-order defects with a possibly higher capture cross-section act as more effective traps resulting in reduced hole mobility.