The structures of the ZnO NPs and NRs layers grown on the In/Si NWs were characterized

by HRTEM. Figure 4a shows a TEM micrograph of a ZnO NPs decorating NWs prepared at 0.5 h of ZnO deposition time. Hexagonal shaped ZnO NPs with different sizes from 10 to 40 nm were observed on the surface of the Si NWs. A magnified HRTEM micrograph of the open square area in Figure 4a is displayed in Figure 4b. A lattice-resolved HRTEM image (inset of Figure 4b) shows the crystal lattice at the interface of Si and ZnO structures. The estimated lattice spacing at two different locations for Si(111) and ZnO(100) crystallographic planes are 3.1 and 2.8 Å, respectively. The average sizes of ZnO NPs measured by the TEM system VX-680 cell line increased to approximately 60 ± 10 nm, which corresponds to the increase of the ZnO growth time to 1 h. The TEM micrograph (Figure 4c) shows the Si NWs are mostly covered by the ZnO NPs. The HRTEM micrograph (Figure 4d) shows the high crystallinity of the grown ZnO NPs. A set of measured lattice spacing with values of approximately 2.8 and 2.5 Å TSA HDAC confirms to the ZnO(100) and (101) crystal planes given by the FFT pattern shown in the inset of Figure 4d. These crystal planes have also been reported by other researchers as a favorable orientation

for ZnO NPs grown on Si NWs [17, 21]. The Si/ZnO hierarchical core-shell NW consists of multiple ZnO NRs which grew laterally from the side of the Si/ZnO core-shell NWs, as revealed in Figure 4e. The lattice-resolved HRTEM image in Figure 4f shows a lattice spacing of approximately 2.6 Å which corresponds to ZnO(002) crystallographic plane. FFT pattern (inset of Figure 4f) indicates that the ZnO NRs are growing along the direction of [0001]. This corresponds with the observation of the growth direction for branching ZnO NRs on the Si wire [27] and undoped ZnO cores previously reported [46]. Figure 4 HRTEM analysis on the Si/ZnO heterostructure NWs. ADP ribosylation factor TEM and HRTEM micrographs of Si/ZnO

core-shell NWs prepared at different ZnO growth time of (a, b) 0.5, (c, d) 1, and (e, f) 1.5 h. Magnified HRTEM micrographs from (b) and (d) are inserted in the respective figures. FFT patterns inserted in (d) and (f) are converted from the appropriate HRTEM micrographs. The crystal structures of the samples were studied using XRD. Figure 5 shows the XRD pattern of the Si/ZnO core-shell NWs prepared at the ZnO growth duration of 1 and 2 h. The Si diffraction peaks are indexed to a face-centered cubic structure [31], while ZnO diffraction peaks are matched to the structure of wurtzite (JCPDS card: 36–1451). The XRD pattern for ZnO nanostructures formed on Si NWs at ZnO growth time of 1 h revealed a similar structure as bulk ZnO [47] with the strongest diffraction peak being at ZnO(101) crystal plane.