Abstract
In this study, ZnO nanowires with diameters ranging from 50 nm to 500 nm have been synthesized hydrothermally on Ag and ZnO seed layers deposited by electron beam evaporation. ZnO nanowires grown on hetero and homo interfaces have been studied by comparing the growth characteristics of (a) ZnO nanowires on the Ag seed layer and (b) ZnO nanowires grown on the ZnO seed layer, respectively. The surface morphology of the as-evaporated seed layers before the nanowire growth has been investigated. Electron backscatter diffraction (EBSD) has been employed to examine the crystallinity of ZnO nanowires. In addition, the integrity of the Ag–ZnO heterointerface has been investigated using high-resolution transmission electron microscopy (HR-TEM). The length, diameter, density, and alignment of nanowires grown on Ag and ZnO seed layers have been studied as a function of growth time from 0.5 hours to 18 hours and precursor concentration from 5 mM to 18 mM. Furthermore, for both the Ag–ZnO nanowire heterostructure and ZnO–ZnO nanowire homostructure, the role of defects in the optical properties in the wavelength range of 517 nm to 900 nm has been studied using photoluminescence (PL) spectroscopy.
Highlights
One dimensional (1D) materials with different properties have been employed to perform a range of functions. 1D Zinc Oxide (ZnO), as a wide band gap semiconductor with a 60 meV binding energy at room temperature,[1] has been considered one of the most promising materials and has been developed for various applications such as piezoelectric,[2,3] optoelectronic,[4,5] and electrochemical devices.[6]
For high-resolution transmission electron microscopy (HR-TEM) sample preparation, the focused ion beam (FIB) technique has been used to extract the ZnO NW–Ag heterointerface and transfer it to a copper grid; the details have been presented in the Electronic supplementary information (ESI).† In addition, PL spectra in the wavelength range of 517 nm to 900 nm have been obtained on both Ag seeded ZnO NWs and ZnO seeded ZnO NWs grown with different growth times and precursor concentrations
ZnO NWs grown on both Ag and ZnO seed layers show [0001] oriented wurtzite crystal structures based on both Electron backscatter diffraction (EBSD) results and HR-TEM results
Summary
One dimensional (1D) materials with different properties have been employed to perform a range of functions. 1D Zinc Oxide (ZnO), as a wide band gap semiconductor with a 60 meV binding energy at room temperature,[1] has been considered one of the most promising materials and has been developed for various applications such as piezoelectric,[2,3] optoelectronic,[4,5] and electrochemical devices.[6]. Compared to sputtering, e-beam evaporation has a better directionality, and it is easier to control the crystalline structure and the surface roughness of the thin- lm.[27] As a very popular deposition method in current very-large-scale (VLS) microfabrication,[28] e-beam evaporation can be an alternative method to prepare high-quality seed layers to grow ZnO NWs, and it is suitable for pattern de nition in high-resolution lithography.[29,30] studies on e-beam evaporated thin- lms as the seed layer to grow ZnO NWs and the mechanism of ZnO NW growth on e-beam evaporated homo and hetero seed layers are still limited in the existing literature. For both the Ag–ZnO NW heterostructure and ZnO–ZnO NW homostructure, the role of defects in the optical properties as a function of growth time and precursor concentration has been studied using photoluminescence (PL) spectroscopy in the wavelength range of 517 nm to 900 nm
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