Abstract
In this study, we report the effects of thermal annealing in nitrogen ambient on the optical and electrical properties of zinc oxide (ZnO) nanorod (NR) arrays for the application in light emission diodes (LED). The single-crystalline ZnO NR array was synthesized on p+-Si (111) substrate without seed layer using simple, low-cost, and low-temperature hydrothermal method. The substrate surface was functionalized by hydrofluoric acid and self-assembled monolayer of octadecyltrimethoxysilane ((CH3 (CH2)17Si(OCH3)3). ZnO NRs were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and micro-photoluminescence (micro-PL). The results of FESEM and XRD indicate that single crystalline ZnO NRs with (002) preferred orientation along the substrate surface is successfully grown on functionalized p+-Si (111) substrate. The current–voltage and electroluminescence (EL) characteristics of the LED show that the most suitable annealing temperature ranges from 400°C to 600°C. Both PL and EL spectra show broadband emissions, ultraviolet and visible (green-yellow) light. The white-like light emission is able to be observed by naked eyes.
Highlights
Zinc oxide (ZnO) is a II-VI compound semiconductor that exhibits n-type conduction due to oxygen deficiency or zinc excess
We investigated on improving the optical properties of the ZnO NRs by annealing the samples in nitrogen ambient under different temperatures
SEM images show that the ZnO NRs are hexagonal crystallographic pillars standing vertically with respect to the substrate surface
Summary
Zinc oxide (ZnO) is a II-VI compound semiconductor that exhibits n-type conduction due to oxygen deficiency or zinc excess. It has a direct wide bandgap of 3.37 eV, large exciton binding energy of 60 meV at room temperature, which is much higher than that of GaN of 25 meV, and defect emissions that cover the whole visible range [1]. In contrast to ZnO and GaN, ZnO has large single crystals that can be grown . It has a very high melting point of 1,977°C, making it difficult to achieve melt to growth. The toxicity and environmental impact are very low than most of the other semiconductors; ZnO is used as a UVblocker in sun lotions or as an additive to human and
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