Dielectric screening versus quantum confinement of phosphorus donors in silicon nanocrystals investigated by magnetic resonance

We monitor the localization of donor wave functions when going from the bulk to nanoscales by electrically detected magnetic resonance of P-doped Si nanocrystal networks. Analysis of the P hyperfine splitting shows that for nanocrystals with radii above ∼6 nm donor localization is dominated by a reduction in dielectric screening relative to the bulk rather than by quantum confinement. Screening effects become negligible only for radii below ∼2 nm, where quantum confinement dominates. Thus, hyperfine interactions can serve as sensitive probes to study basic properties of doped nanocrystals and provide data to critically test theoretical models.