White light emission from the composite system of ZnO/porous Si

We report that the composites of ZnO/porous Si (PS) can exhibit intensively white photoluminescence (PL) under proper excitation wavelength. The PS sample is formed by electrochemical anodization of n-type (111) silicon. ZnO films are then deposited on the PS surface by pulsed laser deposition (PLD). ZnO is transparent in the visible region, so the red PL from PS can be transmitted through the ZnO films. White PL from the ZnO layer on PS can be obtained, which consists of blue-green emission from ZnO and red emission from PS. The x-ray diffraction (XRD) pattern shows that the ZnO films deposited on PS surface are non-crystalline. Due to the roughness of the PS surface, some cracks appear in the ZnO films, which could be seen from the scanning electron microscopy (SEM) images.