Nature, Published online: 07 October 2026; doi:10.1038/d41586-026-02934-2

Semiconductor crystals grow from tiny nuclei, but the position of these nuclei is difficult to control precisely and can affect the crystal’s properties. An approach using ‘etching flux’ has now been developed that constrains the position at which a nucleus forms, enabling spatially programmable growth of large single crystals of semiconducting material.