Nanocomposites and nanomaterials

Influence of growing conditions on the characteristics of silicon nanowires
Yu. Kalashnyk1, A. Klimovskaya1, O. Oberemok1, Yu. Pedchenko1, A. Voroshchenko1, P. Lytvyn1, D. Hourlier2
1 V.E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, 41 pr. Nauki, 03028, Kyiv, Ukraine.
E-mail: yu.kalashnik@gmail.com
2 Institut de'Electronique, de Microélectronique et de Nanotechnologies, Villeneuve de'Ascq, France.

We grow the SiNWs using the method of chemical vapor deposition in a chamber of reduced pressure (CVD technology) using gold as a metal catalyst. Nanowires growing under quasi-equilibrium conditions and non-equilibrium temperature conditions in the growth chamber. Variation of the growth regimes gives the rise to grow different nanowires structures on the substrate.
In quasi-equilibrium conditions we obtained silicon nanowires, uniformly distributed on the substrate. The diameter of the SiNWs ranges from 10 to 200 nanometers, and the length was up to 70 µm. The size of the SiNWs depended on the conditions of the preliminary processing of the substrate in which they grew (the thickness of the golden film, temperature, time of annealing) and growth conditions (the time of growth, the flow of silane, the temperature of the substrate).
To ensure non-equilibrium conditions, we placed a silicon substrate with gold droplets in the growth chamber and heated to the temperature of the silane decomposition. Gold was heated much faster than silicon, and began rapidly diffuse over the surface of the substrate and slowly diffuse inside of the substrate. The diffusion slows down with the onset of the decomposition of silane and the subsequent growth of the nanowires and ends after the substrate temperature is equalized. The growth-seeds and nanostructures were distributed in the form of rings with a central nucleus. The central parts (the cores) have diameters of about 15-20 µm. The rings have a diameter of about 10-15 µm. The nature of the formation of such structures is based on the Liesegang’s effect.

1.	D. Hourlier, A. Klimovskaya at al. Growth of arrays of silicon nanowires with centrosymmetric distribution over silicon substrate // Superlattices and Microstructures. - 2008. - 44. - P. 362-373.