Formation of interstitial silicon defects in Si- and Si,P-doped nanodiamonds and thermal susceptibilities of SiV photoluminescence band.

We have produced two types of synthetic nanodiamonds Si- and Si,P-doped and have characterized the thermal susceptibilities of the spectral band of silicon-vacancy (SiV) centers at approximately 740 nm in each case. The covered temperature range from 295 to 350 K is of interest for thermometry in biological systems. Comparison of the relative brightness of the Si- and Si,P-doped crystals shows that phosphorous significantly increases average concentration and homogeneity of distribution of SiV centers in nanodiamonds. Moreover, linear dependence on temperature of the zero-phonon line width in Si-doped crystals is 0.061(2) nm K but is 0.047(3) nm K, about 35% smaller in Si,P-doped nanodiamonds. This proves control of SiV properties with additional chemical doping and close proximity of Si and P atoms.