New cluster secondary ions for quantitative analysis of the concentration of boron atoms in diamond by time-of-flight secondary-ion mass spectrometry

A new approach to quantitative analysis of the concentration of boron atoms in diamond using secondary ion mass spectrometers with time-of-flight mass analyzers is proposed. Along with the known boron-containing lines (B, BC, BC$_2$), many lines related to cluster secondary ions BC$_ N$ have been found in the mass spectrum; their intensity increases by one or two orders of magnitude when Bi$_3$ probe ions are used. Lines BC$_{4}$, BC$_{6}$, BC$_{2}$, and BC$_{8}$ have the highest intensity (in the descending order); when they are summed, the sensitivity increases by an order of magnitude in comparison with the known mode of detecting BC$_2$. The parameters of the boron $\delta$-layer in single-crystal diamond films grown under optimal conditions have been measured to be unprecedented: the $\delta$-layer width is about 2 nm, and the concentration is 6.4 $\times$ 10$^{20}$ cm$^{-3}$ (the boron concentrations for doped and undoped diamonds differ by four orders of magnitude).