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Metal nanoparticles are promising objects of research, since their properties are significantly different from the bulk material. When analyzing nanoparticles, it is important to study their size, stability, structural features and spatial arrangement. The initial and annealed nanoparticles of silver, formed on a carbon substrate by vacuum-thermal evaporation and having dimensions from 2 nm up to 10 nm, have been studied by using the high resolution electron microscopy method. The classification of their form and structure has been carried out. Among the studied ones the nanoparticles in the shape of a faceted ellipsoid with a polycrystalline structure, coarse nanoparticles with a monocrystalline structure and twins, icosahedral and decahedral nanoparticles with multiple twinning, and also, small single crystalline nanoparticles with dimensions less than 3.5 nm, have been revealed. It has been found that a result of annealing the number of small nanoparticles has been about 2 times decreased and the fraction of nanoparticles with icosahedral and decahedral shapes has been approximately 1.5 times increased. It has been shown that the nanoparticles with sizes less than 5 nm are unstable after a few seconds of exposure to high-energy electrons. For small initial and annealed single crystalline nanoparticles of less than 3 nm size the mean values of the lattice constant have been found by the precise determination of the atomic column centers on their images and the calculation of the local interplanar spacing values between the atoms located in mutually orthogonal (200) and (022) planes. It has been shown that in such nanoparticles both prior and after annealing there had been no noticeable distortions of the crystal structure and their lattice constant had been close to the value, characteristic for bulk silver.
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During formation of silver nanoparticles arrays by condensation to the cold substrate the initial condensate is non-stable. For the formation of non-stable arrays with the form, close to a spherical one, subsequent weak thermal treatment is required. The nanosize state for many substances significantly differs from the mass state. In the work the behavior of the silver nanoparticle array during low-temperature annealing has been shown. Using the atomic-force microscopy the evolution of the silver nanoparticles array, formed on the SiO by the vacuum-thermal evaporation the unheated substrate during in-situ heating up to 200 °C, has been investigated. The qualitative estimate of the temperature influence on the geometry of the nanoparticles arrays has been obtained. It has been experimentally shown that a sharp enlargement of silver nanoparticles and decreasing of their quantity on the surface occurs in a small temperature of (75-100 °C). After statistical processing of the obtained data the average sizes of the formed particles and their density per unit area at each stage of the experiment have been determined and the corresponding dependences have been obtained.
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