A silicon oxide layer was subjected to high dose silicon implantation and to a subsequent high temperature anneal to induce the formation of silicon nanoclusters embedded in the SiO2 host. The sample was analyzed by energy filtered transmission electron microscopy in a cross-sectional configuration. By using the electron energy loss associated with the silicon bulk plasmon excitation, we were able to image the silicon nanoclusters. The corresponding electron intensity was then normalized to the value associated with pure SiO2 and the results were used to measure the clustered silicon concentration at any depth of the SiO2 layer. The data were compared to the silicon excess concentration profile obtained by using the Si L-edge and the O K-edge ionization losses to determine the chemical silicon and oxygen concentration profile.