SEM images of ZnO nanowire arrays grown on FTO substrates with different ZnO seed obtained from (a–f) the spin-coating method, (g–k) the dip-coating method.a,c,e,g,iandkcorrespond to top-view observations,b,d,f,h,jandlcorrespond to cross-sectional views. The insets show high-magnification SEM images