{111} Sigma 3 and {112} Sigma 3 twin boundaries and their junctions in a phosphor-doped cast polycrystalline silicon were investigated by EELS using HREM to study the local electrical properties and impurity effects at these boundaries and junctions. FWHMs of the silicon plasmon-loss peaks are wider at the grain boundary junctions and {112} Sigma 3 twin boundary as compared with other area partly because of the overlapped effect of plasmon loss Of SiO2 and carbon. In the inner-shell edge part of EELS spectrum, the grain boundary junction having distorted structure shows slightly strong intensity at around 110 eV, suggesting the formation of nano-size SiO2, even though the presence of the SiO2 could not be observed by HREM. The effects of carbon K-edge can be recognized in the EELS spectra acquired at {111} Sigma 3 and {112} Sigma 3 boundaries and their junctions, suggesting the grain boundary segregation of carbon atoms. (c) 2007 Elsevier B.V. All rights reserved.