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International projectsSTCU 5513Technological methods

Several  technological methods for synthesis of SiO2:C composite materials are used:

(1) carbonized nano-porous silicon oxide (por-SiO2:C) layers are fabricated by electrochemical etching of monocrystaline silicon wafers followed by successive thermal carbonization in acetylene flow and oxidation by water vapor;

Scheme of the procedure for fabrication of light-emitting por-SiO2:C layers

TEM image of por-SiO2:C layer and real photo of light emission of such kind of material

(2) SiO(x)C(x):H thin films are fabricated by low-temperature oxidation of carbon-rich a-SiC:H thin films deposited by magnetron sputtering of Si or SiC target in argon/hydrocarbon gas mixture. After oxidation in oxygen flow at temperature 500-600 oC these films excibite white light photoluminescence.

(3) SiO2:C nano-powders synthesized by chemical treatment of fumed nano-silica precursor (a-SiO2:H nano-powder) followed by thermal annealing in inert atmosphere;

Chemical treatment is performed so that to replace hydroxyl (-OH) groups with hydrocarbon groups (for example methyl groups, as shown in the picture).

Schematic ilustration of formation of SiO2:CnHm precursor powder

Following thermal annealing of silica-hydrocarbon powder SiO2:CnHm at temperature above 400 oC result in dehydrogenatetion of hydrocarbon radicals and carbon precipitation. Proper treatment results in formation of SiO2:C material that emits strong white light under excitation by violet or UV radiation

Evolution of the color of the powder with increase of the treatment temperature

Photoilustration of light emission from SiO2:C powder under 408 nm LED

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