Îëåêñåíêî Î.Î.
Íàö³îíàëüíèé òåõí³÷íèé óí³âåðñèòåò Óêðà¿íè
" Êè¿âñüêèé ïîë³òåõí³÷íèé ³íñòèòóò "
DIELECTRIC PROPERTIES OF NANOCOMPOSITE SYSTEMS METAL- DIELECTRIC INTRODUCTION
Granular nanocomposites are the metal – dielectric heterogeneous systems consisting of metallic granules of nanometer size, by casual appearance of distributed in a dielectric matrix. These structural features determine the unique and important for practical application electrophysical properties. Unique properties of granular nanocomposites do these materials interesting for microelectronic applications. On their basis materials are created for hybrid microelectronic technology. Namely pastes for internal connections, composite conducting pastes for interconnections, and also protective dielectric pastes, sheeting and other technological materials. In addition they can be used for creation of functional units.
In work the results of research of conductivity and dielectric permeability of nanocomposites are represented metal is dielectric in a UHF-range.
1. Method of experimental researches
Most methods of measuring of conductivity are the contact methods based on measuring of currents and tensions. However much quality of contacts considerably influences on the results of measuring, especially at the low values of conductivity. In addition these methods impose restraints on the geometrical sizes of standard.
Nevertheless, it is known [1; 2] that the most adequate information about the size of conductivity of matters can be got indirect (contactless) methods in basis of which the analysis of electromagnetic properties of material lies in optical or UHF-range.
Measuring was conducted in the range of frequencies of 8 – 12 GHz. For the performance of measuring, the rectangular or cylindrical dielectric sample (1), made from the explored material, with the known geometrical sizes takes place between two parallel metallic plates covered by silver or gold (2) as shown on the fig. 1. For diminishing of the losses brought in by a measuring cell, the surfaces of plates are covered by silver or gold.
One of plates is set with possibility of moving in direction perpendicular to the planes of metallic mirrors and, by means of bar (3), fastened on a micrometrical screw (4), that enables to measure the thickness of dielectric sample.
Fig . 1. Measuring method
This measuring section, through a coaxial cable (5), joins in one of the known charts of measuring of resonances frequencies and own quality factors. Own frequency and own quality factor of the system for the lower E-type of vibrations are determine.
Then on the got values conduct the calculation of dielectric permeability and tangent of angle of dielectric losses and, accordingly, conductivity [2].
2. Experimental researches
Metal-dielectric granular nanocomposite materials are explored in work. As a metallic phase nano powders of aluminum were used, and as a dielectric matrix are polymeric materials with the different values of dielectric permeability.
Samples of nanocomposite materials were made by the method of electro-mechanicals interfusion of nano powder of aluminum with polymeric connective in the liquid state. Hardening of standards took place at a room temperature under constraint and at permanent interfusion.
By the change of aluminum nano powder volume stake in composition, the series of samples were got with different concentration of metallic nano phase in with to the connective dielectric matrix.
The structure of nanocomposite materials was explored by the method of raster electronic microscopy.
3. Results and Discussions
Specific volumes resistances of composite structures are experimentally explored in the frequency range of 8 – 12 GHz. The influencing of volume part of filling factor for electrical properties of metal – dielectric structures studying (fig. 1, 2). The structure of nanocomposite materials was explored by the method of raster electronic microscopy (fig. 3).
For measuring of complex dielectric permeability of material and specific resistance of composite materials with low conductivity used dielectric resonator method.
|
a) real part complex dielectric permeability of material |
b) imaginary part of complex dielectric permeability of material |
|
Fig . 2. Complex dielectric permeability of composite
|
|
|
|
|
|
Fig . 3. Specific conductivity of composite |
Fig . 4. Microstructure of composite |
It is shown that electrophysical properties of nanocomposite structures have percolation character.
The list of references:
1. Gorbachev V.V. Physics of semiconductors and metals / V.V. Gorbachev, P.G . Sinitsin . – M.: High school, 1982. – Ð. 248.
2. Tatarchuk D.D . Measuring of UHF-parameters of materials by the method of E-type dielectric resonator / D.D . Tatarchuk // Electronics and Communications. – 2002. – ¹14. – (Russian) – P. 22 – 23.
3. Insulators, semiconductors and metals By John Clarke Slater, Vol. 3 of Quantum Theory of Molecules and Solids, 1967.
4. Machulyansky A.V . The High Conductivity of Nanoscale Metal Particles / A.V . Machulyansky // Electronics and Communications. – 2007. – P. 1 (Russian) – P. 41 – 45.
5. Machulyansky A.V . Modeling of Super Dispersed Metal-dielectric Systems / A.V . Machulyansky // Electronics and Communications. – 2000. – ¹ 9 (Russian). – P. 123 – 125.