Rapid synthesis of dual-element isotope-enriched 𝛼−Mo⁢O3 crystals by reactive vapor transport

Abstract

In this work, we develop a rapid reactive vapor transport technique to efficiently utilize limited isotopically pure precursors, particularly gaseous 18O2, and synthesize mm-scale, high-quality isotope-enriched crystals within few-minute growth durations. We unlock this capability by using metallic molybdenum precursors with high source temperatures (900∘⁢C) and total pressures (∼1 atm) to maximize precursor efficiency and yield. Subsequently, we grow 𝛼−Mo⁢O3 single crystals with high and uniform enrichment levels of 98Mo and 18O isotopes in several different permutations. As probed by Raman spectroscopy, modest and significant phonon energy redshifts occur following 98Mo and 18O enrichment, respectively. By demonstrating control over both molybdenum and oxygen isotopic enrichments, we establish a powerful tool to advance nanophotonics and thermal management goals using 𝛼−Mo⁢O3. This work is motivated by the possibility to enhance and engineer lattice vibrational mode phenomena including thermal conduction and hyperbolic phonon polariton dispersion—with particular interest in comparing the effects of light and heavy element enrichment.