STRUCTURE AND PHOTOLUMINESCENCE OF ANNEALED SEMIINSULATING POLYCRYSTALLINE SILICON MATERIAL OBTAINED BY DISILANE

Semi-insulating polycrystalline silicon samples from a mixture of disi lane and nitrous oxide were deposited with different oxygen content an d annealed by RTA under different time and temperature conditions. Str uctural characterization by TEM showed that after annealing and in sam ples with high silicon content, the excess of silicon crystallizes in small clusters with diameters between 40-80 Angstrom. As shown by FTIR and XPS, the matrix surrounding the nanocrystals is composed of SiOx and SiO2 regions. A thermodynamic free energy model for the different silicon tetrahedral configurations was applied to the structure of thi s material. The model predicted that phase separation is favoured afte r annealing at high temperature, but some remaining concentrations of suboxide species are present in the whole range of oxygen content, all these results being in agreement with the shell model. Furthermore, p hotoluminescence experiments only showed bands owing to defects, in co ntrast with visible emission reported for nanocrystals of the same siz e. (C) 1997 Elsevier Science S.A.