Seeded Chemical Vapor Transport Growth of Cu2OSeO3

We present an optimized seeded chemical vapor transport method for the growth of Cu2OSeO3 that allows for chemical control in a system with many stable phases to selectively produce large phase-pure single crystals. This method is shown to consistently produce single crystals in the range of 120 to 180 mg. A Wulff construction model of a representative crystal shows that the minimum energy surface is {1 1 0}, followed by {1 0 0}. Analysis of the lowest index planes revealed that cleavage of Se–O bonds has a large energy cost, leading to an overall high surface energy. The seeded chemical vapor transport demonstrated here shows promise for large single crystal growth of other functional materials such as Weyl semimetals, frustrated magnets, and superconductors.