Influence of ion irradiation on the morphology, structure, and optical properties of gold nanoparticles synthesized in SiO2 and Al2O3 dielectric matrices

Irradiation of fused quartz (SiO₂) and sapphire (Al₂O₃) by Ne⁺ and F⁺ ions with medium energies and their subsequent annealing enables us to control the intensity and frequency of surface plasmon resonance in Au nanoparticles (NPs) synthesized in oxide matrices. The control process can be implemented because NPs dissolve during irradiation and undergo partial reconstruction at annealing. The degree of reconstruction depends on the matrix material and the type and dose of ions. It has been found that the difference in the results obtained by means of irradiation with ions with similar masses is substantially affected by the chemical nature of the ions. The composition, morphology, and structure of the unirradiated and irradiated layers are investigated by transmission electron microscopy, X-ray photoelectron spectroscopy, and spectroscopic ellipsometry.     

Nanosize layers of silicon and manganese ferromagnetic alloys deposited from laser plasma

The results of studying random silicon-manganese alloys with Mn concentration increased up to 50 at % and discrete alloys (multilayer structures with silicon and manganese layers 5–20 and 1–5 nm thick, respectively) deposited from laser plasma are presented. Structure and composition were checked by atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. In Si-Mn discrete alloys, the high-level hole conduction with the conventional linear Hall effect was observed. For silicon-manganese random alloy layers with Mn concentration increased up to 50 at %, the hysteresis abnormal Hall effect, magnetooptic Kerr effect and anisotropic dependence between the microwave absorption and magnetic field typical for plane ferromagnets were recorded up to 293 K. Ferromagnetism of homogeneously doped silicon layers is due not to the separation of the second phase with the excess of Mn but with the unusual properties of silicon and manganese alloys prepared in heavily nonequilibrium conditions. Structural measurements of discrete alloys confirmed the presence of the periodic depth distribution of silicon and manganese. The first data about the character of atom mixing near the layer boundaries during the laser synthesis were obtained. Results obtained by applied mathematical and statistical analysis of the sequences of separate photoelectron lines observed during the Si-Mn system ion profiling in depth were given.     

Chemical and phase compositions of silicon oxide films with nanocrystals prepared by carbon ion implantation

The chemical and phase compositions of silicon oxide films with self-assembled nanoclusters prepared by ion implantation of carbon into SiO _x (x < 2) suboxide films with subsequent annealing in a nitrogen atmosphere have been investigated using X-ray photoelectron spectroscopy in combination with depth profiling by ion sputtering. It has been found that the relative concentration of oxygen in the maximum of the distribution of implanted carbon atoms is decreased, whereas the relative concentration of silicon remains almost identical over the depth in the layer containing the implanted carbon. The in-depth distributions of carbon and silicon in different chemical states have been determined. In the regions adjacent to the layer with a maximum carbon content, the annealing results in the formation of silicon oxide layers, which are close in composition to SiO₂ and contain silicon nanocrystals, whereas the implanted layer, in addition to the SiO₂ phase, contains silicon oxide species Si²⁺ and Si³⁺ with stoichiometric formulas SiO and Si₂O₃, respectively. The film contains carbon in the form of SiC and elemental carbon phases. The lower limit of the average size of silicon nanoclusters has been estimated as ∼2 nm. The photoluminescence spectra of the films have been interpreted using the obtained results.