FESEM and TEM images of the vertically grown ZnO NWs. (a) FESEM image (tilted view) of the as-grown ZnO NWs, that are grown vertically to the Si(100) substrate. Inset shows the NWs at higher magnification. (b) and (c) show the typical TEM image and SAED pattern of the as-grown ZnO NWs. The inset of (b) shows the high-resolution lattice image of the corresponding NW.