Fyzikální ústav Akademie věd ČR

Seminar Tuesday, 06/05/2014 13:00 - 13:30

Speakers: Prof. Nikolay Galkin (Institute of Automation and Control Processes of FEB RAS, 5 Radio Str., 690041, Vladivostok, Russia)
Place: Library, Institute of Physics ASCR, Cukrovarnická 10, Praha 6
Presented in English
Organisers: Department of Optical Materials

In presented report short review of nanocomposite structure formation based on embedded nanocrystallites of semiconductor silicides of Fe, Cr, Mg, Mn, Ca in the monocrystalline and poycrystalline silicon in silicon and their electrical and optical properties have been presented. It was shown that b-FeSi₂ and CrSi₂ NCs with sizes (5-20 nm) have a strained crystal structure with lattice constants on 1.0 – 2.5% smaller than those for the bulk silicides. The effect of nanocrystals moving has been observed for b-FeSi₂ and CrSi₂ NCs during the epitaxial growth of silicon top layers. Different motion mechanisms (coalescence by sweeping for b-FeSi2 NCs and low temperature melting for CrSi₂ NCs) during their embedding in monocrystalline Si lattice have been proposed for both systems. The range expansion of the RT EL-signal to 1.2 – 1.6 microns of silicon diode structures with embedded β-FeSi₂ NCs layers was explained by contribution b-FeSi2 NCs with sizes 10-40 nm, quantum size effect of very small b-FeSi₂ NCs (5-7 nm) and dislocation EL signal of D3 and D4 lines. The possibility of the enhancement of near infrared sensitivity of silicide based silicon photodetectors utilizing b-FeSi₂ and CrSi₂ NCs embedded in silicon matrix has been shown. It was demonstrated, that an increase of the b-FeSi2 NCs period quantity and existence in silicon matrix of stressed CrSi₂ NCs result to increase the photoresponse of the mesa-diode in the spectral range down to 0.70 eV (or 1.8 mm) that is very convenience for design of new silicon based NIR optoelectronic couples. Doping process of semiconductor silicide‘s NCs of Mg, inside nanocomposite layers has been developed on the base of ordered superstructures of metals (Ag, Sb) on a silicon substrate. Nanocomposite layers with n- and p-type conductivity have been successfully grown. The huge increase of Seebeck coefficient and power factor in the Si-p/b-FeSi2 NCs/Si-p and Si/Mg2Si NCs/Si nanocomposites has been found as compared with p- or n-type conductivity Si substrate. N- and p-type conductivity nanocomposite heterostructures with high Seebeck coefficient, power factor and increased ZT value in the temperature range of 300-500 K will be soon grown and tested by electrical and thermal conductivity methods.