Role of hexamethylenetetramine concentration on structural, morphological, optical and electrical properties of hydrothermally grown zinc oxide nanorods

J Mater Sci: Mater Electron (2016) 27:1220912215 DOI 10.1007/s10854-016-5376-6

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Web End = Role of hexamethylenetetramine concentration on structural, morphological, optical and electrical properties of hydrothermally grown zinc oxide nanorods

Guru Nisha Narayanan1 Karthigeyan Annamalai1

Received: 3 May 2016 / Accepted: 14 July 2016 / Published online: 21 July 2016 Springer Science+Business Media New York 2016

Abstract Zinc oxide (ZnO) nanorods were grown on the glass substrates using hydrothermal method. Inuence of hexamethylenetetramine (HMTA) concentration on the morphological, structural, optical and electrical properties of ZnO was investigated. Increasing HMTA concentration produces dense growth of nanorods and decreases the diameter from *450 to *150 nm and also modied the hexagonal shape of ZnO nanorods to circular shape. X-ray diffraction spectra revealed that the synthesized ZnO nanorod exhibits wurtzite structure. Shifting of absorbance edge from 3.30 to 3.36 eV with increasing concentration of HMTA was observed in the UVVis spectra. Photoluminescence studies showed the presence of defect related peaks such as zinc interstitial and oxygen vacancies. The observed blue shift in UV emission peak from 387 to 361 nm in photoluminescence spectrum also conrmed the decrease in the size of nanorods. Electrical studies showed the increase in the resistance with the increase in the HMTA concentration from 1.17 to 16.9 kX due to dense and reduced size of nanorod networks.

1 Introduction

Zinc Oxide (ZnO), one of the IIVI metal oxide semiconductors, has been widely investigated as it possesses wide direct band gap of 3.37 eV and large exciton binding energy of 60 meV at room temperature [1] and its potential

applications in light emitting diodes [2], eld emission devices [3], solar cells [4, 5], super capacitors [6, 7], photocatalysis [8, 9] and gas sensors [10, 11]. Preparation of ZnO nanostructures were reported by pulsed laser deposition [12], rf sputtering [13], spray pyrolysis [14], chemical vapor deposition techniques [15] and also through chemical routes [16]. ZnO nanostructures such as nanowires (NW) [17], nanorods (NR) [18], nanobers [19], nanotubes (NT) [20], nanoplates (NP) [21], and nanoparticles [22] have been successfully developed employing these techniques. Among these techniques, hydrothermal approach is a promising one for growing ZnO nanorods due to controlled growth rate, simplicity [23] and its ability to produce various nanostructures [24, 25]....