Rapid synthesis of dual-element isotope-enriched alpha-MoO3 crystals by reactive vapor transport

TL;DR

This paper presents a rapid vapor transport method for synthesizing high-quality, isotope-enriched alpha-MoO3 crystals within minutes, enabling advanced nanophotonics and thermal management applications.

Contribution

It introduces a fast, efficient technique to produce isotope-enriched MoO3 crystals with controlled isotopic composition, improving upon traditional slower methods.

Findings

Achieved mm-scale crystals in minutes using reactive vapor transport.

Demonstrated high and uniform enrichment levels of 98Mo and 18O.

Observed phonon energy shifts correlating with isotope enrichment.

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 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 MoO3 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 fractions, we establish a powerful tool to advance nanophotonics and thermal management goals using MoO3. This work is motivated by the possibility to enhance and engineer lattice vibrational mode phenomena including thermal conduction and hyperbolic phonon polariton (HPhP) dispersion, with particular interest in comparing the effects of light and heavy element enrichment.