Changes in the Structure and Properties of Silicon During Ytterbium Doping: The Results of o Comprehensive Analysis

In this work, a comprehensive study of the structural, chemical and electrophysical properties of monocrystalline silicon (Si) doped with ytterbium (Yb) has been carried out. The alloying was carried out by thermal diffusion at a temperature of 1473 K in high vacuum conditions followed by rapid cooling. Atomic force microscopy (AFM), infrared Fourier spectroscopy (FTIR), deep level spectroscopy (DLTS) and Raman spectroscopy (RAMAN) were used to analyze the samples obtained. AFM images of the surface of the doped samples demonstrated significant changes in topography. The RMS surface roughness increased from less than 10 nm to 60-80 nm, and the maximum height of the irregularities reached 325 nm. These changes are explained by the formation of nanostructures caused by the uneven distribution of ytterbium atoms in the silicon crystal lattice, as well as the occurrence of internal stresses. "IR-Fourier spectroscopy showed a significant decrease in the concentration of optically active oxygen (NOopt ) by 30-40% after doping. This effect is associated with the interaction of ytterbium atoms with silicon and a change in the chemical composition of the material. The RAMAN spectra revealed the formation of new phases and nanocrystallites in the doped samples. Peak shifts and changes in their intensity were detected, indicating a rearrangement of the crystal lattice caused by the introduction of ytterbium. It was calculated that the diffusion coefficient of ytterbium in silicon is 1.9×10-15 cm2/s, which indicates a slow diffusion process characteristic of rare earth metals. Electrical measurements carried out on the MDS-structures showed a shift in the volt-farad characteristics towards positive bias voltages, which is associated with a decrease in the density of surface states at the Si-SiO₂ interface and the appearance of deep levels with an ionization energy of Ec-0.32 eV.