Influence of growth temperature and duration on different properties of ultra-long ZnO nanorods grown by modified chemical bath deposition method

Abstract

In this work, ultra-long ZnO nanorods (NRs) were grown on ZnO buffered Si substrates by using direct heat substrate-modified chemical bath deposition (DHS-MCBD) method. Initially, the growth temperature was varied in the range 140 °C to 250 °C while keeping the time fixed at 4h. In the second stage, the growth temperature was kept fixed at 220 °C and the time was changed from 4h to 8 h. The morphological, structural and optical properties of ZnO NRs at different growth temperatures were investigated by using field emission scanning electron microscope (FESEM), x-ray diffraction (XRD) and photoluminescence (PL) spectroscopy techniques. The surface morphology results revealed the formation of hexagonal-shaped, ultra-long and vertically-aligned ZnO NRs. The average length of the NRs was increased from 5.7 μm to 24.5 μm by increasing the growth temperature from 140 °C to 250 °C. The XRD results specified the formation of c-axis oriented diffraction peak corresponding to hexagonal ZnO NRs in all the samples. The intensity of this peak was increased by increasing the growth temperature up to 220 °C, however, on further increasing the temperature to 250 °C, the c-axis peak intensity was decreased. The PL analysis indicated higher UV to deep level emission intensity ratio (IUV/IDLE) of the NRs grown at 220 °C as compared to the others. Similarly, by changing the growth time from 4h to 8h, the length of ZnO NRs was also increased. The results obtained were correlated and the chemical reactions for ZnO NRs growth were discussed in this paper.