Large substitutional impurity isotope shift in infrared spectra of boron-doped diamond

Isotopic enrichment offers cutting-edge properties of materials. In semiconductors, contributions to physical properties from different isotopes can be routinely and precisely examined by different optical techniques down to a very low relative atomic content in the crystal lattice. In the case of impurity centers this can be as low as a few ppm. We report the splitting of infrared absorption lines caused by the isotopic content of boron acceptors embedded in semiconducting diamond. A blueshift as large as 0.2% of the intracenter transition energy of B-10 relative to the B-11 transitions has been observed in diamond with natural boron abundance. This is a large isotopic shift for hydrogenlike substitutional impurity centers in semiconductors. Also, a much smaller (similar to 0.01%) redshift of B transitions in diamond doped with natural boron has been observed relative to the B-11 transitions in diamond doped by enriched B-11 (up to 99%).