The intensity of ZnO crystal peaks increased with the rise in ZnO growth time to 2 h. In addition, the ZnO(002) crystalline peak selleck inhibitor became more prevalent with longer ZnO growth time. The strong ZnO(002) peak proves the c-axis growth of ZnO along
the  growth direction. This again shows that prolonging the growth time will switch the deposition of ZnO materials from solely expanding the thickness of the shell layer to lateral growth of ZnO NRs out of the Si/ZnO radial which gives a stronger ZnO(002) peak. Figure 5 XRD study on the Si/ZnO heterostructure NWs. XRD pattern of the ZnO nanostructures prepared at ZnO growth time of 1 and 2 h on the In/Si NWs. The PL spectra of the In/Si NWs and ZnO nanostructures deposited on the In/Si NWs at different growth time are depicted in Figure 6. The In/Si NWs (Figure 6a) exhibit orange and red emissions with spectral range
from 500 to 750 nm, centered at Ralimetinib nmr approximately 620 and 690 nm, respectively. The orange (approximately 620 nm) emission was caused by a defect emission due to incomplete oxidation learn more on the surface of the In seeds , while the red (approximately 690 nm) emission is partially related to the quantum confinement effect in Si nanocrystallites surrounding the surface of the Si NWs [34, 36]. Decorating the surface of the In/Si NWs with ZnO NPs creates a broader range of PL ranging from approximately 400 to 750 nm with an additional defect (green) emission from ZnO, centered at approximately 530 nm (Figure 6b). Meanwhile, a weak UV emission with a maximum reading at approximately 380 nm was also observed which is due to excitonic recombination corresponding to the near band edge emission of ZnO. Similar PL spectrum is observed for the ZnO NPs deposited at 1 h (Figure 6c) as well as traces of increment in the green and UV emissions. By increasing the ZnO growth time to 1.5 h, both the green and UV emissions were increased in relation to the suppression in the orange and red emissions. The suppression of the orange and red emissions from the In2O3 and nanocrystallites Si could be due to the full coverage of ZnO nanostructures on the In/Si NWs. Similarly, a change in
the visible PL peak position from approximately 600 to 500 nm was also observed by Bera et al.  for selleck compound the ZnS-coated ZnO NWs. This suggests that the visible emission can be changed by the formation of core-shell NWs. Further increase of the ZnO growth time to 2 h enhanced the UV emission and reduced the green emission of ZnO. Figure 6 PL analysis on the Si/ZnO heterostructure NWs. PL spectra of (a) In/Si NWs and Si/ZnO core-shell NWs prepared at different ZnO growth times of (b) 0.5, (c) 1, (d) 1.5, and (e) 2 h. The green defect emission is normally observed for the ZnO nanostructures in addition to the near band edge emission. Although the origin of the green emission remains questionable, it is generally attributed to the transition of donor-acceptor pair related to the oxygen vacancies [14–16, 50–52].