Abstract <p>The results of X-ray diffraction studies of single-crystal silicon doped with copper are presented. X-ray diffraction data show that the surfaces of the studied samples correspond to the crystallographic orientation (111). The polycrystalline SiO₂ layer consists of various silicon dioxide crystallites characterized by a trigonal lattice with lattice parameters <i>a</i> = <i>b</i> = 4.9762 nm and <i>c</i> = 5.4321 nm and space group <i>P</i>3₂1. The nanocrystallites of silicon phosphide consist of cubic unit cells with a lattice parameter of 0.5692 nm belonging to space group <i>Pa</i>3. Introducing copper atoms into silicon at different temperatures (1000, 1100, and 1200°C) increases the lattice parameters of the <i>n</i>-Si samples. Introducing copper atoms into silicon at 1200°C decreases the intensity of the main structural line by a factor of 10 and increases the intensity of other types of structural reflections as a result of an increased number of impurity atoms. Formation of Cu₂O nanocrystallites with the crystallographic orientation (110) at subcrystallite interfaces occurs due to the introduction of a large number of copper atoms into silicon at 1200°C.</p>