D. A. Tashmukhamedova

Bio: D. A. Tashmukhamedova is an academic researcher from Tashkent State Technical University named after Islam Karimov. The author has contributed to research in topics: Ion implantation & Ion. The author has an hindex of 5, co-authored 16 publications receiving 63 citations.

On the synthesis of nanoscale phases of metal silicides in the near-surface region of silicon and the study of their electronic structures by passing light

Abstract: The band gap E g of nanocrystalline phases NaSi2 and CoSi2 synthesized on the surface and in the near-surface region of silicon by ion implantation in combination with annealing is determined by measuring the intensity of light at different frequencies, passing through the test samples, and by using ultraviolet photoelectron spectroscopy. The nanoscale phases MeSi2 (Me = Na, Co) on the surface of silicon are obtained by the implantation of Me ions with the energy E 0 = 1 keV; and in the near-surface region (at a depth of 15–16 nm), by the implantation of ions with E 0 = 15 keV. Postimplantation annealing is mainly carried out by heating. It is shown that MeSi2 nanocrystalline phases both on the surface and in the near-surface layer are crystallized in the cubic lattice. It is found that E g of the nanocrystalline metal-silicide phases, depending on their size, can range from 0.6 to 1 eV.

Energy spectra of SiO2 nanofilms formed on a silicon surface by ion implantation

Abstract: The topography, composition, and electronic and crystal structures of the surface of SiO2 films fabricated by the implantation of O2+ ions in Si (111) with subsequent annealing are investigated. It is established that at high ion implantation doses (D ≥ 6 × 1016 cm−2), continuous homogeneous polycrystalline SiO2 films form, while at relatively low doses (D = 8 × 1015−4 × 1016 cm−2), SiO2 films with regularly arranged Si nano-areas with a density of 1010–1011 cm−2 form.

Applying low-energy ion implantation in the creation of nanocontacts on the surface of ultrathin semiconductor films

Abstract: A new way for obtaining nanocontacts on the surface of semiconductors using Si (111) thin films as an example is proposed. The essence of the method lies in the fact that, first, cobalt-silicide nanofilms with a thickness of 45–50 A are formed by ion implantation in combination with annealing; then, atoms of the contact metal (Al) are sputtered. The specific resistance of the CoSi2 nanofilms is (2–3) × 10−5 Ω × cm.

Structure and electronic properties of nanoscale phases and nanofilms of metal silicides produced by ion implantation in combination with annealing

Abstract: It is established that ion implantation in combination with annealing makes it possible to produce regularly arranged nanocrystalline phases and continuous films of metal silicides in the surface region of Si. It is shown that silicide nanocrystals and nanofilms crystallize in the cubic lattice. A model of a Si surface with silicide nanocrystals is developed.

Emission and optical properties of SiO2/Si thin films

Abstract: The energy-band parameters and the emission and optical properties of SiO2/Si films of different thicknesses prepared by thermal oxidation and ion bombardment are studied. It is shown that the band gap E g of the SiO2/Si film with a thickness of 30–40 A is 8.8–8.9 eV. In the transition layer, the E g value and secondary-electron emission coefficient σm steadily decrease with increasing depth.

On the synthesis of nanoscale phases of metal silicides in the near-surface region of silicon and the study of their electronic structures by passing light

Abstract: The band gap E g of nanocrystalline phases NaSi2 and CoSi2 synthesized on the surface and in the near-surface region of silicon by ion implantation in combination with annealing is determined by measuring the intensity of light at different frequencies, passing through the test samples, and by using ultraviolet photoelectron spectroscopy. The nanoscale phases MeSi2 (Me = Na, Co) on the surface of silicon are obtained by the implantation of Me ions with the energy E 0 = 1 keV; and in the near-surface region (at a depth of 15–16 nm), by the implantation of ions with E 0 = 15 keV. Postimplantation annealing is mainly carried out by heating. It is shown that MeSi2 nanocrystalline phases both on the surface and in the near-surface layer are crystallized in the cubic lattice. It is found that E g of the nanocrystalline metal-silicide phases, depending on their size, can range from 0.6 to 1 eV.

Energy spectra of SiO2 nanofilms formed on a silicon surface by ion implantation

Abstract: The topography, composition, and electronic and crystal structures of the surface of SiO2 films fabricated by the implantation of O2+ ions in Si (111) with subsequent annealing are investigated. It is established that at high ion implantation doses (D ≥ 6 × 1016 cm−2), continuous homogeneous polycrystalline SiO2 films form, while at relatively low doses (D = 8 × 1015−4 × 1016 cm−2), SiO2 films with regularly arranged Si nano-areas with a density of 1010–1011 cm−2 form.

Ionization-Induced Subcycle Metallization of Nanoparticles in Few-Cycle Pulses

Abstract: Strong-field laser-matter interactions in nanoscale targets offer unique avenues for the generation and detailed characterization of matter under extreme conditions. Field-driven, subcycle ionizati...

On the creation of ordered nuclei by ion bombardment for obtaining nanoscale si structures on the surface of CaF2 films

Abstract: The effect of preliminary low-energy (~1 keV) and low-dose (~1012–1014 cm–2) ion bombardment on the initial stages of growth of Si films on a CaF2/Si surface is investigated. Ordered nanocrystal phases (thickness less than 5–6 monolayers) and homogeneous epitaxial nanofilms (thickness more than 8–10 monolayers) of silicon are shown to be formed after annealing.

Photoelectrochemical Reduction of CO2 to Syngas by Reduced Ag Catalysts on Si Photocathodes

Abstract: The photoelectrochemical reduction of CO2 to syngas that is used for many practical applications has been emerging as a promising technique to relieve the increase of CO2 in the atmosphere. Si has been considered to be one of the most promising materials for photoelectrodes, but the integration of electrocatalysts is essential for the photoelectrochemical reduction of CO2 using Si. We report an enhancement of catalytic activity for CO2 reduction reaction by Ag catalysts of tuned morphology, active sites, and electronic structure through reducing anodic treatment. Our proposed photocathode structure, a SiO2 patterned p-Si photocathode with these reduced Ag catalysts, that was fabricated using electron-beam deposition and electrodeposition methods, provides a low onset-potential of −0.16 V vs. the reversible hydrogen electrode (RHE), a large saturated photocurrent density of −9 mA/cm2 at −1.23 V vs. RHE, and faradaic efficiency for CO of 47% at −0.6 V vs. RHE. This photocathode can produce syngas in the ratio from 1:1 to 1:3, which is an appropriate proportion for practical application. This work presents a new approach for designing photocathodes with a balanced catalytic activity and light absorption to improve the photoelectrochemical application for not only CO2 reduction reaction, but also water splitting or N2 reduction reaction.