"Spicy world of NanoScience"
Nanotechnology Scientific Educational Centre (SEC) was established as a structural department of Dagestan State University.
The SEC was established to co-ordinate and carry out fundamental, applied, and scientific and research studies, as well as to train highly qualified nanotechnology specialists, and to implement the results of the researches into innovative educational programs in place at Dagestan State University.
Core departments and laboratories of the Physics and Chemistry faculties at Dagestan State University, as well as the centre for High Technologies and three laboratories at the Dagestan Scientific Centre of Russian Academy of Sciences, served as the infrastructural foundation for the SEC.
Currently, the Nanotechnology SEC focuses on the following priority scientific areas:
1) synthesis of new materials based on oxides and other compounds;
2) generation of nanopowders and ceramics using the compaction method;
3) generation of thin films and multi-layered structures;
4) material structure and properties studies;
5) creation of a database addressing the properties of nanostructured materials.
The labs used to carry out the scientific projects are provided with state-of-the-art equipment – in particular, a cryogenic complex for to produce liquid nitrogen (Figure 1) necessary ultralow temperature experiments, Ntegra Spectra probe nanolaboratory (Fihure 2), scanning electron microscope with a microanalyser, appliances for producing thin films via chemical transport methods (Figure 3), magnetron sputtering (Figure 4), high-temperature decomposition of organic materials, etc. The laboratories also get to use research equipment of the Analytical Spectroscopy Multiple-Access Centre.
Figure 1. Liquid nitrogen production cryogenic complex
The researches address the fundamental problem of material sciences – the synthesis of materials based on oxides, and identifying regularities in their properties, as well as creating conditions for possible managing these properties using external actions.
Currently, the researches are being carried out due to financial support of the Federal Task Program “Scientific and Pedagogical Resources of Innovative Russia for 2009-2013,” the Analytical Institutional task Program “Development of Scientific Potential of Higher School,” the Russian Foundation for Basic Research grants, and other sources. Priority research areas include the following:
- regularities of formation, peculiarities of structure and physical properties of nanostructured objects considered promising for practical use of the materials;
- regularities of formation of properties and phase states of oxide polycrystalline materials with perovskite structure;
- peculiarities of formation of scattering cross-section of elementary electronic and thermal excitation in metal solid solutions of various types;
- synthesis and exploration of photocatalytic activity of nano-dispersed photocatalysts during dye oxidation under oxygen pressure;
- nonlinear electrophysical properties of polycrystalline ferroelectrics and ferrorelaxers in static and pulsed electric fields;
- experimental and theoretical researches of the structure and properties of transport of solid and fused electrolytes.
Figure 2. NtegraSpectra Probe Laboratory
It should be noted that within the high energy-gap semiconductor family, oxides draw special attention of researchers as they offer a broad range of possible uses. That includes zinc oxide(ZnO) – a promising semiconductor material with a unique set of physicochemical properties. For example, it offers wide perspectives for use in LCD displays, solar converters, low-emission power-saving glass coatings, etc. However, practical implementation of potential possibilities offered by the compound is inhibited due to the lack of reproducible technology of thin ZnO film generation with tailored properties, that are actively applied in acoustoelectronics. Among known piezoelectric semiconductors, zinc oxide has the greatest electromechanical-coupling coefficient which the semiconductor transducer operation efficiency depends on, and is widely used for piezo- and optoelectronics as a thin film on an amorphous substrate. n-ZnO/p-GaN heterostructures have recently been the subject of intensive research – with the purpose of creating highly effective LEDs based on them.
Figure 3. Appliance producing films via magnetron sputttering and gas-cycle synthesis
Compounds with perovskite structure; structures complicated with hydrogen bonds; Si and Ge semiconductors; semiconductor compounds ZnO; fullerenes; carbon nanotubes; as well as MgB2, Y(Ba1-xBex)2Cu3O7-δ and other high-temperature superconductors share an anomaly – negative thermal deformation at low temperature . This anomaly is an evidence of competition of the interatomic bond amplification mechanisms, on average in the atomic lattice, along with the attenuation of bonds between the adjacent atoms at the temperature rise. Such objects are often very sensitive to various external effects with their sensitivity grows vastly with the activation of the mechanism of interatomic interaction forces formation associated with excessive surface energy.
Figure 4. Complex producing films via magnetron sputtering
As a result of identification of the connection between thermal deformation and kinetic properties of condensed media, it was possible to discover the nature of temperature dependencies of such objects and to suggest a way to manage contributions of the aforementioned mechanisms. Use of the latter facilitated generation of new complex oxides Y(Ba1-xBex)2Cu3O7-δ, где х = 0–1, with a wide range of electric properties from high-temperature superconductivity to semiconductors. It is known that relative thermal deformation does not depend on the size of the material and is determined only by the peculiarities of the average interatomic interaction forces in the atomic lattice of the material. Therefore, the use of consequences of the determined linear bond between thermal deformation and kinetic properties of condensed media allows to effectively assess physical properties of relevant nano-objects based on diffraction analysis data.
Nanopowders based on complex yttrium, barium, and beryllium oxides with dispersion ranging from 20 to 100 nm and low apparent density (0.02 g/sm3) were produced by burning nitrate-organic precursors. Figure 5 shows the morphology of nanoparticle agglomerates. Powder compacting method was used to create ceramic materials based on Y(Ba1-xBex)2Cu3O7-δ with various densiti levels including one close to theoretical. There were generated mono- and polycrystalline films from 10 to 500 nm wide, and sandwich structures Te/CdTe, Te/ZnTe, Te/CaF, Te/Al2O3, CdS/ZnO, ZnO/ Y(Ba1-xBex)2Cu3O7-δ, YBe2Cu3O7-δ/ZnO, Si/ Y(Ba1-xBex)2Cu3O7-δ. Properties of Ge-ZnO, Si-ZnO, GaP-ZnO, СdS-ZnO heterostructures were studied, and a capability to improve the diode properties of the heterostructures was demonstrated. Using the magnetron sputtering method on direct current, ZnO films were generated with a high level of lattice perfection and without a columnar structure.
Figure 5. Structure of nanopowders based on
а) YBа2Cu3O7-δ, b) YBа0,5Be0,5Cu3O7-δ, c) YBe2Cu3O7-δ
Currently, Nanotechnology SEC has built laboratory functional devices with particular physicochemical properties (delay lines, gas sensors, ultraviolet radiation sources and detectors, piezo- and photo-transformers). ZnO and Y(Ba1-xBex)2Cu3O7-δ nanofilms and nanolayers with the corresponding structural perfection, composition and properties are promising for producing functional structures. Methods of creating materials based on ZnO and Y(Ba1-xBex)2Cu3O7-δ are patented [2–12].
Interest for nano-dispersed semiconductor oxides is associated with their unique physical properties with their sizes close to 5–10 nm – for example, their unique wettability, sensor and optical properties, biological compatibility, etc. Semiconductor metal oxides show high photocatalytic activity which allows to operate the process of surface, water and air cleaning.
Figure 6. Microphotography of a Cu2O sample
In the course of the project, nanodispersed Fe2O3, Cu2O oxides (Figure 6) and TiO2 nanotubes were synthesised using the electrochemical method allowing to generate high-clean products. The synthesised oxides can be used in various industries, and in particular, to create solar energy conversion elements. Copper oxide (I) is used to dye glass and enamels. It is also a part of paint applied to underwater areas of vehicles of the sea. Such paint prevents the bottom of ship from being covered with seaweed. In addition, cuprite (Cu2O) is a p-type semicondustor with direct energy-gap width of 2.0–2.2 eV; it can find a use in building elements for solar energy conversion .
KAg4I5 and RbAg4I5 superionic conductors based on silver iodite are promising members of the family termed “advanced superionic conductors” (ASIC) . They arouse great interest as they show exceptional conductivity and low junction temperature to the superconductor phase. Superionic conductors are widely applied in various electrochemical systems and devices used for information conversion, storage and transfer.
It was the first time that the study of the dependency of electroconductivity of α-RbAg4I5, α-KAg4I5, α-KCu4I5 and their melts on the electric field strength. In superconducting phases of crystals and their melts, an increase in electric field strength results hitting of in limiting values of high-voltage electroconductivity that surpass the low-voltage numbers by tens of percentage points. At the same time, α-RbAg4I5, α-KAg4I5 demonstrates a long-term post-activation relaxation which, together with the strong field effect, makes them even more attractive for solid-state electrochemical devices.
Ferroelectric ceramics based on solid solutions of lead zirconate – titanate oxides Pb(Zr,Ti)O3 (PZT) have widespread application in various devices and apparatuses of up-to-date technology owing to their superior physical properties and to a possibility to vary them if chemical composition has changed. Determination of regularities in physical properties formation and of opportunities to control them via external exposure serves as a basis for development of high-performance ferropiezoelectric materials and for their manufacturing technique improvement. Special interest has recently been shown for ferroelectric ceramics compounds, where alloying below a certain temperature leads to long-range order derangement, and ordered domains (with a short-range order), according cross-section data, have dimensions of about 10–102 nm. Compounds with such a small correlation radius of polarization fluctuations demonstrate relaxor behavior and are called ferrorelaxors. A characteristic feature of these materials is also the fact that nano-scale polar areas, chaotically located throughout the crystal volume, appear in the smeared phase transition area, nano-scale polar areas being surrounded by paraelectric phase (a nanopolar structure). A heavily deformed paraelectric phase interlayer is formed between closely located polar areas, the interlayer prevents merging of nanopolar areas and formation of ferroelectric domain.
The pulse method of ferropiezoelectric materials polarization has been developed and tested. The method reduces time and power inputs of respective materials polarization by many times. It will find an application in the course of obtaining frequency selective devices of broad spectrum and special-purpose piezoelectric transducers.
A complex of thermal and electrical properties of segneto piezoelectric materials has been investigated. The database (certified by the National Standard Reference Data Service)  can be used when developing high-temperature processes of sintering tailored piezoelectric materials and thermal operation conditions for devices based on them.
Research on static critical behavior of magnetic superlattice models was accomplished with assistance of high-efficient cluster algorithms of the Monte-Carlo Method, all basic static critical indices were calculated, regularities in their changes due to interlayer exchange interaction value were determined. The obtained results enable to establish a complete picture of static critical parameters behavior depending on the interlayer/intralayer exchange interaction relation [16–21].
Priority lines of educational activities are as follows: support to young researchers, user guides edition, arrangement of nanotechnology conferences, schools and workshops, etc.
In the course of research and innovative activity scientific research is coordinated with consolidation of staff and material resources of the Physics, Chemistry, Biology and Ecology Faculties at DSU and the DRS RAS with developments in the “Nanotechnologies” area on the experimental basis of multi-access centers at DSU and DRC RAS and in creating competitive science-intensive. Scientific and technical cooperation is performed with research, RD, engineering organizations and industrial enterprises, foundations and other structures for the purpose of solving the most important scientific and technical, and educational problems, expansion of international scientific and technical cooperation with educational institutions and foreign companies with the view of integrating into the world system of science and education.
Master’s training programs (full-time training) were elaborated at the Subdepartments of Physics and Chemistry at DSU and the following special training courses are delivered on the following guidelines:
011200.68 – “Physics” – educational master’s program on nanosystem physics – nanosystem physics essentials, physical experiment technique, probe local spectroscopy; nanosystem physics, transport in nanosystems, nanostructures magnetic properties, chemical and electrochemical methods of particle formation, physics and technology of composites, X-ray structural analysis;
210100 – “Electronics and Nanoelectronics” – educational master’s program on semiconductors and dielectrics physics – nanoelectronics elements and devices, physical nanoelectronics, high energy-gap semiconductors; pressing problems of contemporary electronics and nanoelectronics, semiconductors and dielectrics physics, physics and technology of ceramic materials и and composites, promising techniques of epitaxial technology, physics and technology of electric transition;
020100.68 – “Chemistry” – educational master’s program on guideline 020104 “Physical Chemistry” – quantum mechanics and quantum chemistry, physical methods of investigation, coordination chemistry, superionic conductor electrochemistry.
Laboratory practical training sessions were elaborated and experimental research laboratories “Technology of nano- microstructured materials”, “Methods of research of structure and properties of nano- and microstructured materials”, “Microstructure and physical characteristics of functional materials” were established.
The publishing house of the University issued the following educational and user’s guides: “Obtainin nanopwders Y(Ba1-xBex)2Cu3O7-δ via chemical technology methods (laboratory practical training session)», “Obtaining nanostructured films and semiconducting layers from gaseous phase (laboratory practical training session)». The book “Matter Structure” is in print.
Ready for publication: “Nanosystem physics: kinetic and magnetic properties”, “Background energy spectrum and thermal properties of condensed media”, “Conductors electronic structure and properties”.
All-Russian Conferences take place in the framework of SEC (Scientific Educational Center) “Physical Electronics” and “Innovatika”. The International Conference “Phase Transitions, Critical and Nonlinear Phenomena in Condensed Media» takes place on the basis of Dagestan Research Center, Russian Academy of Sciecnes.
M.Kh. Rabadanov, D.K. Palchaev, A.B. Isaev
Federal State Budgetary Educational Institution of Higher Professional Education “Dagestan State University”,
43a, M. Gadzhiev str., 367001, Makhachkala