By hot-filament (HF) chemical vapor deposition (CVD), heavily boron (B)-doped single-crystal diamond (100)
filmswere fabricated and their structural and electrical properties were studied. Wedid not observe the soot formation,
which is frequently observed and limits the performances in the case of microwave plasma (MWP) CVD.
The B concentration was successfully controlled over the range from 1019 to 1021 cm−3. Hillock-free films were
obtained, whose mean surface roughness measured by atomic force microscopy (AFM) was less than 0.1 nm.
From the reciprocal space mapping (RSM) around 113 diamond reflection, it was revealed that the films possess
the smaller lattice expansion than that expected from the Vegard's law. The room-temperature resistivity was
decreased lower than 1mΩ·cmfor B concentration ~1021 cm−3. These results indicate that the HFCVD possesses
large potential for fabricating the device-grade p+ diamond.