Transition levels of acceptor impurities in ZnO crystals by DFT-LCAO calculations

This research was partly supported by the Kazakhstan Science Project № AP05134367«Synthesis of nanocrystals in track templates of SiO2/Si for sensory, nano-and optoelectronic applications» and Latvian Super Cluster (LASC), installed in the Institute of Solid State Physics (ISSP) of the University of Latvia. Authors are indebted to D. Gryaznov, A. Popov and A. Dauletbekova for stimulating discussions.Large scale ab-initio calculations are carried out to study the charge state transition levels of nitrogen and phosphorus impurity defects in zinc oxide crystals using the DFT-LCAO approximation as implemented into the CRYSTAL computer code. It is shown that at a high concentration of defects (close location of defects) their formation energy is underestimated due to a significant delocalization of the charge within the supercell. After inclusion the energy offset correction and defect-defective interaction, the formation energy is improved, in a comparison with that calculated in a large supercell. The optical transition levels obtained by a direct calculation confirm the experimental observation: nitrogen and phosphorus impurities are deep acceptor centers with large formation energy in a charged state and, therefore, cannot serve as the effective source of hole charge. The obtained results are in good agreement with the previous theoretical work, in which other calculation methods were used, and are capable of qualitatively describing the energy characteristics of the charged defects.University of Latvia; Institute of Solid State Physics, Chinese Academy of Sciences; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

ITO Thin Films for Low-Resistance Gas Sensors

This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP08856540). The research was carried out with the support of a grant under the Decree of the Government of the Russian Federation No. 220 of 9 April 2010 (Agreement No. 075-15-2022-1132 of 1 July 2022). In addition, this research was partly performed at the Institute of Solid State Physics, University of Latvia (ISSP UL). ISSP UL, as the Centre of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under Grant Agreement No. 739508, project CAMART2.Indium tin oxide thin films were deposited by magnetron sputtering on ceramic aluminum nitride substrates and were annealed at temperatures of 500 °C and 600 °C. The structural, optical, electrically conductive and gas-sensitive properties of indium tin oxide thin films were studied. The possibility of developing sensors with low nominal resistance and relatively high sensitivity to gases was shown. The resistance of indium tin oxide thin films annealed at 500 °C in pure dry air did not exceed 350 Ohms and dropped by about 2 times when increasing the annealing temperature to 100 °C. Indium tin oxide thin films annealed at 500 °C were characterized by high sensitivity to gases. The maximum responses to 2000 ppm hydrogen, 1000 ppm ammonia and 100 ppm nitrogen dioxide for these films were 2.21 arbitrary units, 2.39 arbitrary units and 2.14 arbitrary units at operating temperatures of 400 °C, 350 °C and 350 °C, respectively. These films were characterized by short response and recovery times. The drift of indium tin oxide thin-film gas-sensitive characteristics during cyclic exposure to reducing gases did not exceed 1%. A qualitative model of the sensory effect is proposed. © 2022 by the authors. --//-- Published under the CC BY 4.0 license.Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP08856540); ISSP UL, as the Centre of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under Grant Agreement No. 739508, project CAMART2

This content has been downloaded from IOPscience. Please scroll down to see the full text. Hydrogen adsorption on the ZnO surface: ab initio hybrid density functional linear combination of atomic orbitals calculations Hydrogen adsorption on the ZnO ( ) su

Abstract Hydrogen atoms unavoidably presented in ZnO samples or thin films during their synthesis considerably affect electrical conductivity. Results of first principles hybrid functional linear combination of atomic orbitals calculations are discussed for hydrogen atoms incorporated in bulk or adsorbed upon non-polar ZnO (1100) surfaces. The energy of H incorporation, atomic relaxation, electronic density redistribution and modification of the electronic structure are compared for both surface adsorption and bulk absorption. It is shown that hydrogen forms a strong bonding with the surface O ions (E ads = 2.7 eV) whereas its incorporation into bulk is energetically quite unfavorable. Hydrogen adsorption reduces the surface energy. Surface hydrogen atoms are very shallow donors, thus contributing to the electronic conductivity and ZnO metallization

Study of β-Ga2O3 Ceramics Synthesized under Powerful Electron Beam

This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP14870696). Financial support in Latvia was provided by ERAF Project Nr. 1.1.1.1/20/A/057. In addition, J.P and A.I.P. thank the Institute of Solid State Physics, University of Latvia (ISSP UL). ISSP UL as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART2.The synthesis of β-Ga2O3 ceramic was achieved using high-energy electron beams for the first time. The irradiation of gallium oxide powder in a copper crucible using a 1.4 MeV electron beam resulted in a monolithic ceramic structure, eliminating powder particles and imperfections. The synthesized β-Ga2O3 ceramic exhibited a close-to-ideal composition of O/Ga in a 3:2 ratio. X-ray diffraction analysis confirmed a monoclinic structure (space group C2/m) that matched the reference diagram before and after annealing. Photoluminescence spectra revealed multiple luminescence peaks at blue (~2.7 eV) and UV (3.3, 3.4, 3.8 eV) wavelengths for the synthesized ceramic and commercial crystals. Raman spectroscopy confirmed the bonding modes in the synthesized ceramic. The electron beam-assisted method offers a rapid and cost-effective approach for β-Ga2O3 ceramic production without requiring additional equipment or complex manipulations. This method holds promise for fabricating refractory ceramics with high melting points, both doped and undoped. --//-- This is an open access article Usseinov, A.B.; Karipbayev, Z.T.; Purans, J.; Kakimov, A.B.; Bakytkyzy, A.; Zhunusbekov, A.M.; Koketai, T.A.; Kozlovskyi, A.L.; Suchikova, Y.; Popov, A.I. Study of β-Ga2O3 Ceramics Synthesized under Powerful Electron Beam. Materials 2023, 16, 6997. https://doi.org/10.3390/ma16216997 published under the CC BY 4.0 licence.Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP14870696); ERAF Project Nr. 1.1.1.1/20/A/057; the Institute of Solid State Physics, University of Latvia (ISSP UL). ISSP UL as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART2

New Method of Synthesis of ZnSe2O5 Nanocrystals

Секция 4. Формирование наноматериалов и наноструктур = Section 4. Formation of Nanomaterials and NanostructuresThe paper presents the results of an experimental and theoretical study of zinc diselenide nanocrystals obtained by electrochemical deposition in а-SiO2/Si-n track template. The track template SiO2/Si was obtained by irradiation on a DC-60 cyclotron with Xe ions with an energy of 200 MeV (Φ = 10 8 ions/cm2) followed by chemical etching in an aqueous solution of hydrofluoric acid (HF). Electrochemical deposition (ECD) in the track template was carried out in potentiostatic mode. The surface of the samples after deposition was examined using a JSM 7500F scanning electron microscope. X-ray diffraction analysis (XRD) was performed using a D8 ADVANCE ECO X-ray diffractometer. According to X-ray diffraction data, electrodeposition of zinc in the a-SiO2/Si-n track template led to the formation of ZnSe2O5 nanocrystals with an orthorhombic crystal structure. The experimental parameters of the crystal lattice, the density of the crystal, the effective charge, and the population of the chemical bond are in good agreement with the results of quantum chemical calculations performed in the approximation of linear combinations of atomic orbitals and other literature data.The work was performed within the framework of the grant project AP05134367 “Synthesis of nanocrystals in SiO2/Si track templates for sensory, nano - and optoelectronic applications”. The authors are grateful to prof. A. Akylbekov and prof. M. Zdorovets for valuable comments and advice

New Method of Synthesis of ZnSe2O5 Nanocrystals

Секция 4. Формирование наноматериалов и наноструктур = Section 4. Formation of Nanomaterials and NanostructuresThe paper presents the results of an experimental and theoretical study of zinc diselenide nanocrystals obtained by electrochemical deposition in а-SiO2/Si-n track template. The track template SiO2/Si was obtained by irradiation on a DC-60 cyclotron with Xe ions with an energy of 200 MeV (Φ = 10 8 ions/cm2) followed by chemical etching in an aqueous solution of hydrofluoric acid (HF). Electrochemical deposition (ECD) in the track template was carried out in potentiostatic mode. The surface of the samples after deposition was examined using a JSM 7500F scanning electron microscope. X-ray diffraction analysis (XRD) was performed using a D8 ADVANCE ECO X-ray diffractometer. According to X-ray diffraction data, electrodeposition of zinc in the a-SiO2/Si-n track template led to the formation of ZnSe2O5 nanocrystals with an orthorhombic crystal structure. The experimental parameters of the crystal lattice, the density of the crystal, the effective charge, and the population of the chemical bond are in good agreement with the results of quantum chemical calculations performed in the approximation of linear combinations of atomic orbitals and other literature data.The work was performed within the framework of the grant project AP05134367 “Synthesis of nanocrystals in SiO2/Si track templates for sensory, nano - and optoelectronic applications”. The authors are grateful to prof. A. Akylbekov and prof. M. Zdorovets for valuable comments and advice