"PREPARATION AND CHARACTERIZATION OF POROUS ZnO NANOSTRUCTURES GROWN ONTO SILICON SUBSTRATE"

Abstract

"Zinc oxide (ZnO) thin film (approximately 1.1 μm) was synthesized onto a Si(100) substrate by radio frequency (rf) sputtering with 200 W rf power for 120 min. The porous nanostructure of the film was prepared through electrochemical etching with electrolyte solution containing ethanol and nitric acid at a current density of 50 mA/cm2 and constant etching time of 120 s. Scanning electron microscopy images showed that the ZnO nanoparticles featured plate-like shape and covered the entire Si(100) substrate. After the porous process, the surface of the ZnO film became smooth, the plates or large particles disappeared, and nanosized pores were uniformly distributed. X-ray diffraction patterns confirmed that the ZnO/Si(100) thin film exhibited higher crystallinity, with hexagonal phase growing toward the c axis, than that of the porous ZnO/Si(100) nanostructure. The photoluminescence (PL) spectrum showed that the intensity of the near-band edge of the ZnO/Si peak was higher than that of the P–ZnO/Si peak. Furthermore, the number of defects in P–ZnO/Si(100) increased when the ratio of PL intensity for IUV to Idefect decreased from 36.17 for ZnO/Si sample to 1.44 for porous ZnO/Si."