Isotope Enrichment in Laser-Ablation Plumes and Commensurately Deposited Thin Films

A highly efficient isotope enrichment process is observed directly in laser-ablation plumes generated from ultrafast laser pulses focused on a solid surface. Data are presented for boron nitride and gallium nitride targets using laser pulses of 150--200 fs at 780 nm wavelength. Isotope ratios for B and Ga are observed in a time-of-flight spherical-sector electrostatic analyzer. Enrichment factors of 2 or more above natural abundance are observed for the ratios of B¹⁰/B¹¹ as well as for Ga⁶⁹/Ga⁷¹. These same plumes are used to deposit isotopically enriched films of boron nitride on silicon.