Evgeny Buntov

Low-temperature photoluminescence of ion-implanted SiO 2 :Sn + films and glasses

Low-temperature photoluminescence spectroscopy with pulsed synchrotron excitation is applied to study the regularities of excitation and relaxation of both point defects and nanoparticles formed by tin implantation into SiO2 films and glasses. It has been found that tin implantation followed by air and nitrogen annealing yields the formation of α-Sn nanoclusters and nonstoichiometric SnOx nanoparticles, while a stable phase of SnO2 does not appear. Alternative channels of luminescence excitation are revealed for nanoclusters, including energy transfer from excitons and electron-hole pairs of the host SiO2 matrix.

Synchrotron-Excited Photoluminescence Spectroscopy of Silicon- and Carbon-Containing Quantum Dots in Low Dimensional SiO_{2} Matrices

A comprehensive method to study semiconductor nanoparticles in thin film SiO\(_{2}\) matrices has been developed. Selective and high-intensity synchrotron excitation allows the investigation of the nanoparticles energy structure. It is shown that the interference fringes affecting the optical excitation spectra of thin films may be neutralized by means of a special numerical technique. The spectral and kinetic properties of the Si, C, and SiC quantum dots (QD) formed by ion implantation in thin silica films were studied in details. Photoluminescence thermal quenching is shown to contain two stages and is dominated by Street law at low temperatures. Several indirect QD excitation mechanisms are realized, involving point defects, free, and self-trapped SiO\(_{2}\) matrix excitons. An exciton-assisted mechanism is dominating at helium temperatures. A resonant energy transfer mechanism taking place in the silica matrix reveals average defect-QD distance of 6–9 nm. A direct excitation channel is found only for carbon nanoclusters. An overall scheme of energy levels and optical transitions in the “matrix-cluster” system is proposed.

Interference effects in the UV(VUV)-excited luminescence spectroscopy of thin dielectric films

The problem of exciting UV and VUV light interference affecting experimental photoluminescence excitation spectra is analysed for the case of thin transparent films containing arbitrarily distributed emission centres. A numerical technique and supplied software aimed at modelling the phenomenon and correcting the distorted spectra are proposed. Successful restoration results of the experimental synchrotron data for ion-implanted silica films show that the suggested method has high potential.

Photoluminescence of implantation-induced defects in SiO2:Pb+ glasses

The luminescence of quartz glass with implanted Pb+ ions is investigated by time-resolved photoluminescence spectroscopy under synchrotron excitation. It is established that the glass layer modified with ions represents a microheterogeneous medium with a variable content of implanted ions predominantly in the form of Pb2+. Three different types of emission centers are detected that are created by radiation-induced defects of the SiO2 matrix and localized electronic states of the amorphous lead-silicate phase.

Ionization effects in Si/SiO2: Li, Na, K implanted structures under the impact of high-energy α particles

The method of thermally stimulated electron emission is applied in order to investigate ionization processes and defect formation in Si/SiO2 structures under the impact of high-energy α particles. The implantation of Si/SiO2 films with Li+, Na+, and K+ alkali-metal ions is found to contribute to the formation of active emission L centers in the modified oxide layer, which provides sensitivity to α radiation. The parameters of the emission centers are identified and analyzed. It is shown than Si/SiO2: Li heterostructures could be used to detect α radiation.

Optically Stimulated Electron Emission from Surface States of SiO2:Ge Films

Thin 30 nm SiO2 films on silicon substrate implanted with Ge+ ions and flash-annealed at 900°C are investigated by means of optically stimulated electron emission (OSEE). The materials under study may find a number of technological applications in optical devices and ultraviolet sensors. Samples attestation was performed by electron microscopy and x-ray photoelectron spectroscopy (XPS). XPS data revealed strong dependence between the germanium atoms state and annealing time. The application of Urbach rule and power Kane dependence allowed to fit OSEE spectra at different excitation energy ranges and to retrieve the important structure and energy parameters. Observed correlations between parameter values of Urbach-and Kane-related models suggest the implantation-induced changeover of both the vibronic subsystem and energy band structure.