  Boron arsenide (BAs) with a zinc blende structure has recently been
discovered to exhibit unusual and ultrahigh thermal conductivity (k), providing
a new outlook for research on BAs and other high thermal conductivity
materials. Technology for BAs crystal growth has been continuously improving,
however, the influence of boron isotopes, pure or mixed, on the thermal
conductivity in BAs is still not completely clear. Here we report detailed
studies on the growth of single crystals of BAs with different isotopic ratios
and demonstrate that the k of isotopically pure BAs is at least 10% higher than
that of BAs grown from natural B. Raman spectroscopy characterization shows
differences in scattering among various BAs samples. The presented results will
be helpful in guiding further studies on the influence of isotopes on
optimizing k in BAs.
