Electron energy loss spectroscpy (EELS) spectra and atomic column images we
re obtained from a dissociated 60 degrees misfit dislocation at the GexSi1-
x substrate interface of a strained Si quantum well. Silicon 2p(3/2) EELS s
pectra from the stacking fault show splitting of the L-1 conduction band mi
nimum caused by third-neighbor interactions at the fault. Spectra from the
30 degrees dislocation show a similar splitting as well as in-gap defect el
ectronic states. Spectra from the 90 degrees dislocation also show evidence
of in-gap states but do not show the L-1 splitting. An extended core struc
ture based on a double period pairing reconstruction may be able to explain
this lack of L-1 splitting.