A co-sputtering system was used to deposit silicon nanoclusters embedded in zinc oxide matrix (Si:ZnO) at low temperature without post-annealing. By adjusting the radio frequency power of the Si target during co-sputtering, Si:ZnO films with various crystallographic structures can be obtained. Silicon nanoclusters embedded in the zinc oxide matrix were examined using a high-resolution transmission electron microscope, x-ray diffractometer, and Fourier transformation infrared spectrometry. By comparing with photoluminescence spectra, we can clearly identify quantum confinement effect of silicon nanoclusters embedded in the ZnO matrix.