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Home Material Sciences Structure and some properties nanosized and nanostructured objects

Structure and some properties nanosized and nanostructured objects


Results of researches of structure and thermalphysical properties of thin films and crystals of the small sizes (Аu, Ag, Al, Ni, Re, Pb, In, C60) are discussed. Thermal conductivity (λ,), thermal diffusivity (K), thermal expansion (α), cpecific heat (C), total emissivity (ε), mean square displacement of atoms, Debyе temperature, some aspects of melting and crystallization of thin films are investigated.

Experimental methods of studying of the specified properties in wide Interval of thickness t (1–100 nm), temperatures Т (4,2–700 K), structural conditions (a monocrystal, polycrystal, amorphous condition) are developed. The information about structure and the specified properties it is received, in the core, by method of transaction higher energy electron diffraction by the analysis of position, intensity and a profile of the electron diffraction lines. For definition thermal conductivities and thermal diffusivity films heated up inside electron diffraction chamber. The temperature of the films computed from electron diffraction pictures by coefficient of thermal expansion.

Dimensional, structural and substructural effects are investigated. This effects make for distinctions in thermalphysical properties thin films and bulk. It is established, that thermal conductivity of thin films is less of heat conductivity of the bulk. Distinctions in values λ and λ0 depend on a temperature interval of researches, thickness of the films, their structures and can reach several orders of the value.

In an interval 300–4,2 K thermal conductivity of the films monotonously decreases with decrease of the temperature. The maximum of thermal conductivity for bulk metals at low temperatures, in films is not observed. For temperatures 80–300 K thermal resistivity of thin films is well described by expression

λ-1= B/T +C,

where B/T =Wo – residual thermal resistivity, C= Wi – ideal thermal resistivity.

Value Wi are the same for poly- and monocrystal films, does not depend on thickness and coincides with value for bulk.Lorentz's ratio in Wiedemann-Franz-Lorentz law is experimentally determinated. Lorentz's ratio of thin films for the investigated interval of thickness, temperatures, structural states does not differ from classical Sommerfeld value. Total emissivity ε of thin films is less, than ε0 of bulk metal. Value of ε is monotonously increase with increase of thickness, coming nearer to value ε0. As well as for bulk metals, value ε linearly increase with increasing of the temperature.

Distinction in values of coefficient of thermal expansion α, mean square displacement of the thin films and bulk metals are established. Enlarged values of α and root-mean-square displacement of films are caused by influence of external and internal (due to nanoporosity) surfaces. From dependence α on thickness (t <10 nm) of thin films the estimation of coefficient of linear expansion αs for a surface (Аu, С60) is estimated. The influence of thickness and grain size on thermal diffusivity is found. The value K of thin films changes similarly to change of value λ.

Innovative Aspect and Main Advantages

New electron-optical methods of studying thermalphysical properties nanosized objects are offered and developed. The main advantage of the offered techniques of research of properties consists that they allow to supervise structure and phase composition of nanosized bodies during thermophysical experiments.

For the first time the investigations of the thermalphysical properties of thin free from substrates films are carried out. Dependences above mentioned properties of thin films on the thickness, temperature, a structural state are experimentally established. The reasons of distinction in properties of thin films and bulk metals are established.

Areas of Application

The information about thermalphysical characteristics nanosized and nanostructured bodies, are a basis for thermel calculations in numerous areas where thin-film objects and compositions on their basis with different functional destinations are used: micro and nanoelectronics, computer technik, optics, thin-film devices, coverings, catalysts, sensors, etc.

Thin free from substrate thin films with known thermo-physical characteristics can are used as nanocalorimetre. By means of such nanocalorimetre the heating of thin films under electron beam is investigated.

Thickness dependence of thermal expansion of thin C60
Fig. 1 Thickness dependence of thermal expansion of thin C60 films

Stage of Development

Now data on stationary and non-stationary temperature fields free of thin films and their properties are used for development of new methods of investigation of thermo-physical properties of films with thickness t>102 nm, multilayered films, films with amorphous structure.

Contact Details

National technical university "Kharkov polytechnical institute"
Ukraine, 61002, Kharkov, Frunze st. , 21.
D. Sc. Pugachov Anatoliy Ph.
Tel: +38(057) 707-6831
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it


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