Growth and characterization of ZnO nanorods grown on porous silicon substrates prepared with different etching times

Self-assembly of densely packed ZnO nanorods were grown on porous silicon (PS) substrates by chemical bath deposition. The structural and optical properties of the fabricated ZnO nanostructures on PS substrates prepared with different etching times were systematically studied. Field emission scanning electron microscopy (FESEM) revealed that the self-assembly of densely packed ZnO nanorods occurred on the pore walls, inside the pores, and on the surface of PS substrates. FEEM images indicated that the average diameter and length of the ZnO nanorods increased 100 to 200 nm and 600 to 1200 nm with increased etching time from 10 min to 20 min, respectively. X-ray diffraction indicated that the intensity of the ZnO (002) peak increased with increased etching time from 10 min to 15 min, and then decreased with further increased etching time to 20 min. The photoluminescence spectra exhibited a strong UV emission peak located from 379 nm to 381 nm and a visible region emission peak located from 500 nm to 700 nm. The highest intensity ratio (I-UV/I-DLE) was obtained using the PS substrate prepared with etching time of 15 min.