Unintentional tungsten incorporation in diamond during hot-filament chemical vapor deposition

Abstract

Hot-filament chemical vapor deposition exhibits high potential for scaled-up diamond growth. However, contamination from filament materials may adversely affect diamond quality. In this study, we investigated the effects of off-axis (100) planes on impurity incorporation. Tungsten atoms at concentration levels of 10¹⁸ cm^-3 were unintentionally incorporated as impurities from filament wires used; this was confirmed by secondary ion mass spectroscopy. The incorporated amount did not depend on the off-axis angle of substrate, which ranged from 0 to 5°. The incorporation mechanism is discussed on the basis of the obtained experimental results. It is suggested that tungsten atoms are incorporated preferentially at facet faces rather than at step edges.