Selective patterning of ZnO nanorods on silicon substrates using nanoimprint lithography

Mi-Hee Jung,Hyoyoung Lee

doi:10.1186/1556-276x-6-159

Abstract

In this research, nanoimprint lithography (NIL) was used for patterning crystalline zinc oxide (ZnO) nanorods on the silicon substrate. To fabricate nano-patterned ZnO nanorods, patterning of an n-octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) on SiO2 substrate was prepared by the polymer mask using NI. The ZnO seed layer was selectively coated only on the hydrophilic SiO2 surface, not on the hydrophobic OTS SAMs surface. The substrate patterned with the ZnO seed layer was treated with the oxygen plasma to oxidize the silicon surface. It was found that the nucleation and initial growth of the crystalline ZnO were proceeded only on the ZnO seed layer, not on the silicon oxide surface. ZnO photoluminescence spectra showed that ZnO nanorods grown from the seed layer treated with plasma showed lower intensity than those untreated with plasma at 378 nm, but higher intensity at 605 nm. It is indicated that the seed layer treated with plasma produced ZnO nanorods that had a more oxygen vacancy than those grown from seed layer untreated with plasma. Since the oxygen vacancies on ZnO nanorods serve as strong binding sites for absorption of various organic and inorganic molecules. Consequently, a nano-patterning of the crystalline ZnO nanorods grown from the seed layer treated with plasma may give the versatile applications for the electronics devices.

Highlights

Zinc oxide (ZnO) nanorods have been widely investigated in applications such as ultraviolet nanolaser sources, gas sensors, solar cells, and field emission display devices because they have a direct band gap of 3.37 eV and a large exciton binding energy of 60 meV
It was found that the nucleation and initial growth of the crystalline ZnO were accelerated on the ZnO seed layer, not on the oxidized SiO2 surfaces
In conclusions, nanoimprint lithography (NIL) was used for patterning crystalline ZnO nanorods on the silicon substrate

Summary

Introduction

Zinc oxide (ZnO) nanorods have been widely investigated in applications such as ultraviolet nanolaser sources, gas sensors, solar cells, and field emission display devices because they have a direct band gap of 3.37 eV and a large exciton binding energy of 60 meV. The aligned growth of ZnO nanorods has been successfully achieved on solid substrates via a vapor-liquid-solid (VLS) process with the use of gold and tin as catalysts [1]. The VLS process may risk introducing catalyst residual atoms into the ZnO nanorods, which is incompatible with silicon technology and requires heat treatment at high temperatures, which can damage substances already present on the. A solution method for patterning the ZnO nanorods using the selfassembled monolayer (SAM) template was reported. Julia et al [3] demonstrated the direct growth of the ZnO nanorods on silver films from aqueous solution using the organic template because the ZnO nucleation was inhibited through appropriate complexation with the carboxylate end groups of ω-alkanethiol SAM molecules on the silver substrate. Koumoto et al [4] reported that pre-patterned SAMs of a hydrophobic end group led effectively to pattern a ZnO nanocrystal

Methods

Results

Conclusion