Yu. Yu. Lebedinskii

Generation of thorium ions by laser ablation and inductively coupled plasma techniques for optical nuclear spectroscopy

Single- and double-charged 232Th and 229Th ions were produced by laser ablation of solid-state thorium compounds and by inductively coupled plasma techniques with mass-spectrometry analysis from liquid solutions of thorium. The latter method was found to be more applicable for producing ions of radioactive 229Th for laser experiments when searching for the energy value of the isomeric nuclear transition.

The Formation of Submonolayer Thorium Coatings on a Silicon Oxide Surface by Electrochemical Deposition

Data are reported on the mechanisms of the formation of submonolayer coatings based on thorium oxide on the surface of Si(111) single crystal with natural oxide as a result of electrochemical deposition. It is experimentally shown that the deposition of thorium atoms from an acetone solution of Th(NO3)4 onto the surface of natural silicon oxide leads to the formation of defects in the thin silicon oxide layer, which is accompanied by the deposition of thorium nanoclusters onto a pure silicon surface. The observed effects have been qualitatively explained assuming the breakdown of natural silicon oxide due to the presence of an electrical double layer in the near-surface region of the cathode.

The band structure of submonolayer thorium coatings on a silicon oxide surface

Data are reported on the electronic structure of thorium-containing clusters formed on the surface of natural silicon oxide via electrochemical deposition. The mutual arrangement of bands in the clusters and silicon oxide substrate is restored with the use of X-ray photoelectron spectroscopy and electron energy loss spectroscopy. It is concluded that the studied cluster/substrate system may be promising for investigating the low-lying isomeric nuclear transition in 229Th isotope.

Investigation of the electronic properties of Au nanoclusters in SiO2 by combined scanning tunneling/atomic force microscopy

The tunneling of electrons through Au nanoc lusters formed by pulsed laser deposition in a SiO2 thin film on a Si substrate has been investigated by combined scanning/atomic force microscopy (STM/AFM). Conducting Pt-coated Si cantilevers were used. The feedback was maintained via the AFM channel, and the current-voltage (I-V) characteristics of the tunnel contact between the AFM probe and the n+-Si substrate through a =4-nm-thick SiO2 film with Au nanoclusters =2 nm in diameter were measured simultaneously. The current image of the structure contained areas of increased current (tunnel-current channels) 2–15 nm in size, related to tunneling of electrons through Au nanoclusters in SiO2. The I-V characteristics recorded in the tunnel-current channels exhibit specific features related to the Coulomb blockade of electron tunneling through Au nanoclusters.

The size dependence of thermal EMF for Au, Pd, and Pt nanoclusters deposited onto highly oriented pyrolitic graphite surface

Data are presented on the tunnel current-voltage characteristics of gold, palladium, and platinum nanoclusters formed by pulsed laser deposition on the surface of highly oriented pyrolytic graphite. Differential tunnel current-voltage characteristics measured by scanning tunnel spectroscopy have been used to restore the size dependences of the thermal emf values of the studied nanoclusters. The behavior of the thermal emf of the nanoclusters as depending on their sizes has been found to depend on the nature of a metal. The data obtained have been analyzed.

Experimental treatments for the investigation of nuclear optical transition in Thorium-229

An original preparation technique of the thorium films by electrochemical deposition from thorium nitrate solution on different substrate is reported. It was found that electrochemical deposition of thorium on the metal surface provides the formation of adherent continuous films, while the deposition on the semiconductor substrates leads to the formation of thorium island films. The origin of the observed thorium films formation and the results on the investigation of thorium films on Si(111) and polycrystalline Cu surfaces by XPS and LEIS are discussed.

Changes of structure and composition of a zinc ion-implanted silicon surface during nanoparticle formation upon thermal treatment

Data from investigating the formation of nanoparticles (NPs) on a surface of silicon wafers after zinc ion implantation and thermal annealing are presented. The investigation is conducted by means of trans-mission electron microscopy, electron diffraction analysis, energy dispersive microanalysis, scanning tunneling microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. It is found that on their surfaces, the implanted samples have only films of amorphous silicon containing implanted zinc, oxygen, and carbon contamination. Thermal treatment in the range of 400–800°C leads to the formation NP with 20–50 nm wide and 10 nm tall on a wafer’s surface, plus a silicon oxide layer about 20 nm thick. NPs are composed of zinc compounds of the ZnO, ZnSiO3, or Zn2SiO4 types. These NPs disappear after annealing at 1000°C.

Formation of local thorium silicate compound by electrochemical deposition from an acetone solution of thorium nitrate

The results of the study of local formation (diameter of deposited area is about 100 μm) of thorium oxide coatings on SiO2/Si(001) surface by electrochemical deposition are presented. It was found that the electrochemical deposition of thorium atoms from an acetone solution of Th(NO3)4 on silicon surface lead to the formation of thorium-based films. The results of surface analysis by local X-ray photoelectron spectroscopy and X-ray photoemission indicate that these films contain of thorium-, silicon-, oxygen- and carbon-based compounds. After 30 h of annealing at 1350 °C in atmosphere carbon pulled completely, and the compound transforms into thorium silicate films ThSiO4 (Huttonite). Our primary study of ThSiO4 compound by reflection electron energy loss spectroscopy showed that this system have energy gap ~7.7 eV and can be useful for further research of «nuclear clocks» as well as for «nuclear battery».Graphical Abstract