Structural and photoluminescence studies on catalytic growth of silicon/zinc oxide heterostructure nanowires

Su Kong Chong,Chang Fu Dee,Saadah Abdul Rahman

doi:10.1186/1556-276x-8-174

Abstract

Silicon/zinc oxide (Si/ZnO) core-shell nanowires (NWs) were prepared on a p-type Si(111) substrate using a two-step growth process. First, indium seed-coated Si NWs (In/Si NWs) were synthesized using a plasma-assisted hot-wire chemical vapor deposition technique. This was then followed by the growth of a ZnO nanostructure shell layer using a vapor transport and condensation method. By varying the ZnO growth time from 0.5 to 2 h, different morphologies of ZnO nanostructures, such as ZnO nanoparticles, ZnO shell layer, and ZnO nanorods were grown on the In/Si NWs. The In seeds were believed to act as centers to attract the ZnO molecule vapors, further inducing the lateral growth of ZnO nanorods from the Si/ZnO core-shell NWs via a vapor-liquid-solid mechanism. The ZnO nanorods had a tendency to grow in the direction of [0001] as indicated by X-ray diffraction and high resolution transmission electron microscopy analyses. We showed that the Si/ZnO core-shell NWs exhibit a broad visible emission ranging from 400 to 750 nm due to the combination of emissions from oxygen vacancies in ZnO and In2O3 structures and nanocrystallite Si on the Si NWs. The hierarchical growth of straight ZnO nanorods on the core-shell NWs eventually reduced the defect (green) emission and enhanced the near band edge (ultraviolet) emission of the ZnO.

Highlights

One-dimensional semiconductor nanowires (NWs) have gained tremendous attention owing to their unique optical and electrical properties, which can be applied in nanophotonics and nanoelectronics [1,2]
TEM (Figure 1c) and high-resolution transmission electron microscopy (HRTEM) (Figure 1d) micrographs reveal the cone-shaped In seeds with sizes varying from 8 to 50 nm, which are evenly distributed on the surface of the NWs
The high sticky coefficient of In seeds [38] allows it to act as centers to collect vaporized zinc oxide (ZnO) molecules/atoms, which nucleate to form ZnO nanostructures on the Si NWs

Summary

Introduction

One-dimensional semiconductor nanowires (NWs) have gained tremendous attention owing to their unique optical and electrical properties, which can be applied in nanophotonics and nanoelectronics [1,2]. Among the semiconductor NWs, silicon (Si) and zinc oxide (ZnO) NWs are leading in numerous energy-related applications, especially in the fields of optics [3,4], photovoltaic [5,6], and field emission [7,8]. Nanocrystalline Si as well as Si NWs can produce red emission due to the quantum confinement effect [9,10]. This makes them applicable in photonics [3]. ZnO nanorods (NRs) are known to exhibit efficient ultraviolet (UV) and visible green emissions at room temperature [11].

Methods

Results

Conclusion