Formation of electrical dipoles during agglomeration of uncharged particles of hydrogenated silicon

A new phenomenon of the formation of agglomerates having electric dipoles b y agglomeration of originally uncharged aerosol particles is reported. The aerosol particles of hydrogenated silicon are formed via silane pyrolysis i n a flow reactor. The size and morphology of agglomerates were analyzed by a transmission electron microscope. The agglomerate radius increased from 0 .3 to 6 mum with the coagulation time increasing from 0.1 to 200 s (for T = 873 K). The mass M of these agglomerates is connected with the radius R vi a the equation M(g) = 8.5 x 10(-14) x [R(mum)](1.65). An imaging system cou pled with a TV setup was used for direct observation of agglomerate coagula tion and investigation of agglomerate movement in the electric field. The e xperimental results testify that the agglomerates are electric dipoles. It is suggested that this dipole moment arises due to the difference in Fermi energy of primary particles. The dipole moment is similar to 3.5 x 10(-12) (units of CGSE) for the agglomerates with the radius R similar to 0.5 mum ( T = 873 K). This dipole moment corresponds to the Fermi energy difference f or coagulating particles similar to 0.08 V. (C) 2000 Elsevier Science Ltd. All rights reserved.